MASTER Publications Catalog March 2023 PDF

Technical Publications Catalog
March 2023
Table of Contents
Index of AGMA Current Standards and Information Sheets ...................................................................... 1
Index of AGMA Standards and Information Sheets by Topic .................................................................... 5
Aerospace ......................................................................................................................................... 5
Calibration and Measurement Uncertainty ......................................................................................... 5
Couplings .......................................................................................................................................... 5
Design and Assembly – Bevel ........................................................................................................... 5
Design – Fine Pitch ........................................................................................................................... 5
Design – Spur and Helical ................................................................................................................. 5
Design – Wormgears......................................................................................................................... 5
Drive Components............................................................................................................................. 6
Enclosed Drives ................................................................................................................................ 6
Failure Modes ................................................................................................................................... 6
High Speed Units .............................................................................................................................. 6
Inspection and Tolerances................................................................................................................. 6
Lubrication ........................................................................................................................................ 6
Materials ........................................................................................................................................... 6
Metric Usage ..................................................................................................................................... 7
Mill Drives ......................................................................................................................................... 7
Nomenclature .................................................................................................................................... 7
Plastics Gears ................................................................................................................................... 7
Powder Metallurgy Gears .................................................................................................................. 7
Proportions........................................................................................................................................ 7
Rating: Spur, Helical and Bevel Gears ............................................................................................... 7
Sound and Vibration .......................................................................................................................... 8
Splines .............................................................................................................................................. 8
Style Manual ..................................................................................................................................... 8
Thermal............................................................................................................................................. 8
Vehicle .............................................................................................................................................. 8
Wind Turbine Units ............................................................................................................................ 8
Wormgears ....................................................................................................................................... 8
AGMA Standards and Information Sheets................................................................................................ 9
ISO Standards, Technical Reports, and Technical Specifications by ISO Technical Committee 60 ......... 24
Fall Technical Meeting Papers: 2000–2021............................................................................................ 27
2022 PAPERS................................................................................................................................. 27
2021 PAPERS................................................................................................................................. 32
2020 PAPERS................................................................................................................................. 39
2019 PAPERS................................................................................................................................. 43
2018 PAPERS................................................................................................................................. 52
2017 PAPERS................................................................................................................................. 57
2016 PAPERS................................................................................................................................. 60
2015 PAPERS................................................................................................................................. 63
2014 PAPERS................................................................................................................................. 73
2013 PAPERS................................................................................................................................. 78
2012 PAPERS................................................................................................................................. 85
2011 PAPERS................................................................................................................................. 93
2010 PAPERS............................................................................................................................... 102
2009 PAPERS............................................................................................................................... 108
2008 PAPERS............................................................................................................................... 112
2007 PAPERS............................................................................................................................... 116
2006 PAPERS............................................................................................................................... 121
2005 PAPERS............................................................................................................................... 124
2004 PAPERS............................................................................................................................... 128
2002 PAPERS............................................................................................................................... 131
2001 PAPERS............................................................................................................................... 133
Index of AGMA Withdrawn Standards and Information Sheets ............................................................. 136
Obsolete and withdrawn documents should not be used; please use replacements.
Most historical documents are available for purchase. Contact AGMA Headquarters for pricing and availability.
AGMA Publications Catalog i March 2023

American Gear Manufacturers Association
AGMA is a voluntary association of companies, consultants and academicians with a direct interest in the
design, manufacture, and application of gears and flexible couplings. AGMA was founded in 1916 by nine
companies in response to the market demand for standardized gear products; it remains a member- and
market-driven organization to this day. AGMA provides a wide variety of services to the gear industry and
its customers and conducts numerous programs that support these services. Some of these services and
programs are:
• EVENTS:
o FALL TECHNIAL MEETING (FTM) –AGMA’s annual Fall Technical Meeting (FTM) is the
perfect forum in which to share this cutting-edge research and to disperse knowledge for
the benefit of the industry. It provides engineers with the opportunity to communicate
ideas with other experts in the industry making innovation fundamental to the rise of
modern mechanical technology.
o MOTION + POWER TECHNOLOGY (MPT) EXPO – the MPT connects the top
manufacturers, suppliers, buyers, and experts in the mechanical, electrical, and fluid
power industries.
• STANDARDS: AGMA develops all U.S. gear-related standards through an open process under
the authorization of the American National Standards Institute (ANSI).
• ISO PARTICIPATION: AGMA is Secretariat to TC60, the technical committee responsible for
developing all international gear standards. TC60 is an International Organization of
Standardization (ISO) committee.
• MARKET REPORTS AND STATISTICS: AGMA’s Operating Ratio Report, Wage & Benefit
Survey, and Monthly Market Trend Reports help you stay competitive by giving you up-to-date
information on the gear industry.
• TECHNICAL COMMITTEE MEETINGS: AGMA’s Committee meetings are the core of the open
AGMA standard writing process keeping members abreast of new developments while ensuring
AGMA standards are kept current.
• EDUCATION: AGMA supports the professional development of the gear manufacturing
workforce that, in turn, will enhance the manufacturing and distribution of member company
products. We offer face-to-face, online, and webinar formats; leading the industry in gear
education and training, while embracing the expanded use of technology to reach our learners
anytime, anywhere.
• AGMA’s e-NEWSLETTERS: AGMA offers timely and useful information to engage members and
non-members alike.
If you would like additional information about our programs, or on how to become a member of AGMA,
please contact AGMA Headquarters.
American Gear Manufacturers Association

1001 N. Fairfax Street, Suite 500
Alexandria, VA 22314
Phone: (703) 684-0211

FAX: (703) 684-0242
E-Mail: tech@agma.org
website: www.agma.org
Technology Driven. Globally Connected.
AGMA Publications Catalog ii March 2023

How to Purchase Documents
Unless otherwise indicated, AGMA Standards, Information Sheets and papers presented at Fall Technical
Meetings are available for purchase, in electronic form, through the AGMA website, www.agma.org. Current
document pricing is also available on the AGMA website.
Index of AGMA Current Standards and Information Sheets

See index on page 136 for the list of Withdrawn documents
Number Title Page

AGMA 900-J20 Style Manual for the Preparation of Standards, Information Sheets 9
and Editorial Manuals
AGMA 901-A92 Procedure for the Preliminary Design of Minimum Volume Gears 9
AGMA 904-C96 Metric Usage 9
AGMA 905-A17 Inspection of Molded Plastic Gears 9
AGMA 908-B89 Geometry Factors for Determining the Pitting Resistance and 9
Bending Strength of Spur, Helical and Herringbone Gear Teeth
AGMA 909-A06 Specifications for Molded Plastic Gears 9
AGMA 910-D12 Formats for Fine-Pitch Gear Specification Data 9
AGMA 911-B21 Design Guidelines for Aerospace Gear Systems 10
AGMA 913-A98 Method for Specifying the Geometry of Spur and Helical Gears 10
AGMA 914-B04 Gear Sound Manual – Part I: Fundamentals of Sound as Related to 10
Gears; Part II: Sources, Specifications and Levels of Gear Sound;
Part III: Gear Noise Control
AGMA 915-2-B20 Inspection Practices – Part 2: Double Flank Radial Composite 10
Measurements
AGMA 915-3-A99 Inspection Practices – Gear Blanks, Shaft Center Distance and 10
Parallelism
AGMA 916-A19 Face Gears with Intersecting Perpendicular Axes 10
AGMA 917-B97 Design Manual for Parallel Shaft Fine-Pitch Gearing 10
AGMA 918-A93 Numerical Examples Demonstrating the Procedures for Calculating 11
Geometry Factors for Spur and Helical Gears
AGMA 919-1-A14 Condition Monitoring and Diagnostics of Gear Units and Open 11
Gears: Part 1 – Basics
AGMA 920-B15 Materials for Plastic Gears 11
AGMA 922-A96 Load Classification and Service Factors for Flexible Couplings 11
AGMA 923-C22 Metallurgical Specifications for Steel and Cast Iron Gearing 11
AGMA 925-B22 Effect of Tribology and Lubrication on Gear Surface Distress 11
AGMA 926-C99 Recommended Practice for Carburized Aerospace Gearing 11
AGMA 927-A01 Load Distribution Factors – Analytical Methods for Cylindrical Gears 11
AGMA 929-B22 Calculation of Bevel Gear Top Land, Slot Widths and Cutter Edge 12
Radii
AGMA 930-A05 Calculated Bending Load Capacity of Powder Metallurgy (P/M) 12
External Spur Gears
AGMA Publications Catalog 1 March 2023

Number Title Page
AGMA 932-A05 Rating the Pitting Resistance and Bending Strength of Hypoid Gears 12
AGMA 933-B03 Basic Gear Geometry 12
AGMA 935-A05 Recommendations Relative to the Evaluation of Radial Composite 12
Gear Double Flank Testers
AGMA 937-A12 Aerospace Bevel Gears 12
AGMA 938-A05 Shot Peening of Gears 12
AGMA 939-A07 Austempered Ductile Iron for Gears 12
AGMA 940-A09 Double Helical Epicyclic Gear Units 13
AGMA 942-A12 Metallurgical Specifications for Powder Metallurgy, PM, Steel 13
Gearing
AGMA 943-A22 Tolerances for Spur and Helical Racks 13
AGMA 944-A19 Mechanisms of Powder Metal PM Gear Failures 13
AGMA 945-1-B20 Splines – Design and Application 13
AGMA 945-2-B20 Splines – Design and Application (Inch Edition) 13
AGMA 946-A21 Test Methods for Plastic Gears 13
AGMA 955-A22 Guidance for Industrial Gear Lubrication 13
AGMA ISO 10064-1-A21 Code of Inspection Practice – Part 1: Measurement of Cylindrical 14
Gear Tooth Flanks
AGMA ISO 10064-5-A06 Code of Inspection Practice – Part 5: Recommendations Relative to 14
Evaluation of Gear Measuring Instruments
AGMA ISO 10064-6-A10 Code of Inspection Practice – Part 6: Bevel Gear Measurement 14
Methods
AGMA ISO 14179-1 Gear Reducers – Thermal Capacity Based on ISO/TR 14179-1 14
AGMA ISO 18792-A19 Lubrication of industrial gear drives 14
AGMA ISO 22849-A12 Design Recommendations for Bevel Gears 14
ANSI/AGMA 1003-H07 Tooth Proportions for Fine-Pitch Spur and Helical Gears 14
ANSI/AGMA 1006-A97 Tooth Proportions for Plastic Gears 15
ANSI/AGMA 1010-F14 Appearance of Gear Teeth – Terminology of Wear and Failure 15
ANSI/AGMA 1012-G05 Gear Nomenclature, Definitions of Terms with Symbols 15
ANSI/AGMA 1102-C19 Tolerance Specification for Gear Hobs 15
ANSI/AGMA 1103-H07 Tooth Proportions for Fine-Pitch Spur and Helical Gears (Metric 15
Edition)
ANSI/AGMA 1104-A09 Tolerance Specification for Shaper Cutters 15
ANSI/AGMA 1106-A97 Tooth Proportions for Plastic Gears 15
ANSI/AGMA 1107-A19 Tolerance Specification for Form Milling 15
ANSI/AGMA 2001-D04 Fundamental Rating Factors and Calculation Methods for Involute 16
Spur and Helical Gear Teeth
ANSI/AGMA 2002-D19 Tooth Thickness and Backlash Measurement of Cylindrical Involute 16
Gearing

Number Title Page
ANSI/AGMA 2003-D19 Rating the Pitting Resistance and Bending Strength of Generated 16
Straight Bevel, Zerol Bevel, and Spiral Bevel Gear Teeth)
ANSI/AGMA 2004-C08 Gear Materials, Heat Treatment and Processing Manual 16
ANSI/AGMA 2008-D11 Assembling Bevel Gears 16
ANSI/AGMA 2011-B14 Cylindrical Wormgearing Tolerance and Inspection Methods 16
ANSI/AGMA 2101-D04 Fundamental Rating Factors and Calculation Methods for Involute 17
Spur and Helical Gear Teeth (Metric)
ANSI/AGMA 2111-A98 Cylindrical Wormgearing Tolerance and Inspection Methods (Metric) 17
ANSI/AGMA 2116-A05 Evaluation of Double Flank Testers for Radial Composite 17
Measurement of Gears
ANSI/AGMA 6000-C20 Specification for Measurement of Linear Vibration on Gear Units 17
ANSI/AGMA 6001-F19 Design and Selection of Components for Enclosed Gear Drives 17
ANSI/AGMA 6002-D20 Design Guide for Vehicle Spur and Helical Gears 17
ANSI/AGMA 6006-B20 Standard for Design and Specification of Gearboxes for Wind 17
Turbines
ANSI/AGMA 6008-A98 Specifications for Powder Metallurgy Gears 18
ANSI/AGMA 6011-J14 Specification for High Speed Helical Gear Units 18
ANSI/AGMA 6013-B16 Standard for Industrial Enclosed Gear Drives 18
ANSI/AGMA 6014-B15 Gear Power Rating for Cylindrical Shell and Trunnion Supported 18
Equipment
ANSI/AGMA 6015-A13 Power Rating of Single and Double Helical Gearing for Rolling 18
Mill Service
ANSI/AGMA 6022-D19 Standard for Design Manual for Cylindrical Wormgearing 18
ANSI/AGMA 6025-E19 Sound for Enclosed Helical, Herringbone and Spiral Bevel Gear 18
Drives
ANSI/AGMA 6032-B13 Standard for Marine Gear Units: Rating and Application for Spur and 19
Helical Gear Teeth
ANSI/AGMA 6033-C08 Materials for Marine Propulsion Gearing 19
ANSI/AGMA 6034-C21 Practice for Enclosed Cylindrical Wormgear Speed Reducers and 19
Gearmotors
ANSI/AGMA 6035-A02 Design, Rating and Application of Industrial Globoidal Wormgearing 19
ANSI/AGMA 6101-F19 Design and Selection of Components for Enclosed Gear Drives 19
(Metric)
ANSI/AGMA 6102-D20 Design Guide for Vehicle Spur and Helical Gears (Metric) 19
ANSI/AGMA 6113-B16 Standard for Industrial Enclosed Drives (Metric) 19
ANSI/AGMA 6114-B15 Gear Power Rating for Cylindrical Shell and Trunnion Supported 20
Equipment (Metric)
ANSI/AGMA 6115-A13 Power Rating of Single and Double Helical Gearing for Rolling Mill 20
Service (Metric Edition)
ANSI/AGMA 6123-C16 Design Manual for Enclosed Epicyclic Gear Drives 20

Number Title Page
ANSI/AGMA 6132-B13 Standard for Marine Gear Units: Rating and Application for Spur and 20
Helical Gear Teeth (Metric Edition)
ANSI/AGMA 6133-C08 Materials for Marine Propulsion Gearing (Metric) 20
ANSI/AGMA 6134-C21 Practice for Enclosed Cylindrical Wormgear Speed Reducers and 20
Gearmotors (Metric Edition)
ANSI/AGMA 6135-A02 Design, Rating and Application of Industrial Globoidal Wormgearing 20
(Metric)
ANSI/AGMA 9000-D11 Flexible Couplings – Potential Unbalance Classification 21
ANSI/AGMA 9001-C18 Flexible Couplings – Lubrication 21
ANSI/AGMA 9002-C14 Bores and Keyways for Flexible Couplings (Inch Series) 21
ANSI/AGMA 9003-C17 Flexible Couplings – Keyless Fits 21
ANSI/AGMA 9004-B08 Flexible Couplings – Mass Elastic Properties and Other 21
Characteristics
ANSI/AGMA 9005-F16 Industrial Gear Lubrication 21
ANSI/AGMA 9006-A16 Flexible Couplings – Basis for Rating 21
ANSI/AGMA 9008-B00 Flexible Couplings – Gear Type – Flange Dimensions, Inch Series 22
ANSI/AGMA 9009-E20 Flexible Couplings – Nomenclature for Flexible Couplings 22
ANSI/AGMA 9103-C17 Flexible Couplings – Keyless Fits (Metric Edition) 22
ANSI/AGMA 9104-A06 Flexible Couplings – Mass Elastic Properties and Other 22
Characteristics (Metric Edition)
ANSI/AGMA 9110-A11 Flexible Couplings – Potential Unbalance Classification 22
(Metric Edition)
ANSI/AGMA 9112-B15 Bores and Keyways for Flexible Couplings (Metric Series) 22
ANSI/AGMA ISO 1328-1- Cylindrical gears – ISO system of flank tolerance classification – 22
B14 Part 1: Definitions and allowable values of deviations relevant to
flanks of gear teeth
ANSI/AGMA ISO 1328-2- Cylindrical Gears — ISO System of Flank Tolerance Classification 22
A21 — Part 2: Definitions and Allowable Values of Double Flank Radial
Composite Deviations
ANSI/AGMA ISO 14104- Gears – Surface Temper Etch Inspection After Grinding, Chemical 23
A17 Method
ANSI/AGMA ISO 17485- Bevel Gears – ISO System of Accuracy 23
A08
Supplement to Supplemental Tables for ANSI/AGMA ISO 17485-A08, Bevel Gears 23
ANSI/AGMA ISO 17485- – ISO System of Accuracy – Tolerance Tables
A08
ANSI/AGMA ISO 18653- Gears – Evaluation of Instruments for the Measurement of 23
A06 Individual Gears
ANSI/AGMA ISO 23509- Bevel and Hypoid Gear Geometry 23
B17

Index of AGMA Standards and Information Sheets by Topic
Aerospace
AGMA 911 Design Guidelines for Aerospace Gear Systems
AGMA 926 Recommended Practice for Carburized Aerospace Gearing
AGMA 937 Aerospace Bevel Gears
Calibration and Measurement Uncertainty

AGMA 935 Recommendations Relative to the Evaluation of Radial Composite Gear Double Flank Testers
ANSI/AGMA 2116, Evaluation of Double Flank Testers for Radial Composite Measurement of Gears
AGMA ISO 10064-5, Code of Inspection Practice – Part 5: Recommendations Relative to Evaluation of Gear
Measuring Instruments
ANSI/AGMA ISO 18653, Gears – Evaluation of Instruments for the Measurement of Individual Gears
Couplings
AGMA 922 Load Classification and Service Factors for Flexible Couplings
ANSI/AGMA 9000 Flexible Couplings – Potential Unbalance Classification
ANSI/AGMA 9001 Flexible Couplings – Lubrication
ANSI/AGMA 9002 Bores and Keyways for Flexible Couplings (Inch Series)
ANSI/AGMA 9003 Flexible Couplings – Keyless Fits
ANSI/AGMA 9004 Flexible Couplings – Mass Elastic Properties and Other Characteristics
ANSI/AGMA 9006 Flexible Couplings – Basis for Rating
ANSI/AGMA 9008 Flexible Couplings – Gear Type – Flange Dimensions, Inch Series
ANSI/AGMA 9009 Flexible Couplings – Nomenclature for Flexible Couplings
ANSI/AGMA 9103 Flexible Couplings – Keyless Fits (Metric Edition)
ANSI/AGMA 9104 Flexible Couplings – Mass Elastic Properties and Other Characteristics (Metric Edition)
ANSI/AGMA 9110 Flexible Couplings – Potential Unbalance Classification (Metric Edition)
ANSI/AGMA 9112 Bores and Keyways for Flexible Couplings (Metric Series)
Design and Assembly – Bevel

AGMA 929 Calculation of Bevel Gear Top Land, Slot Widths and Cutter Edge Radii
AGMA ISO 10064-6 Code of Inspection Practice – Part 6: Bevel Gear Measurement Methods
AGMA ISO 22849 Design Recommendations for Bevel Gears
ANSI/AGMA 2008 Assembling Bevel Gears
ANSI/AGMA ISO 17485 Bevel Gears – ISO System of Accuracy
ANSI/AGMA ISO 23509 Bevel and Hypoid Gear Geometry
Design – Fine Pitch

AGMA 910 Formats for Fine-Pitch Gear Specification Data
AGMA 916 Face Gears with Intersecting Perpendicular Axes
AGMA 917 Design Manual for Parallel Shaft Fine-Pitch Gearing
Design – Spur and Helical

AGMA 901 A Rational Procedure for the Preliminary Design of Minimum Volume Gears
AGMA 913 Method for Specifying the Geometry of Spur and Helical Gears
Design – Wormgears
ANSI/AGMA 6022 Design Manual for Cylindrical Wormgearing

Drive Components
ANSI/AGMA 6001 Design and Selection of Components for Enclosed Gear Drives
ANSI/AGMA 6101 Design and Selection of Components for Enclosed Gear Drives (Metric Edition)
Enclosed Drives
AGMA 940 Double Helical Epicyclic Gear Units
AGMA ISO 14179-1 Gear Reducers – Thermal Capacity Based on ISO/TR 14179-1
ANSI/AGMA 6013 Standard for Industrial Enclosed Gear Drives
ANSI/AGMA 6113 Standard for Industrial Enclosed Gear Drives (Metric)
ANSI/AGMA 6123 Design Manual for Enclosed Epicyclic Gear Drives (Metric)
Failure Modes
AGMA 944-A19, Mechanisms of Powder Metal, PM, Gear Failures
ANSI/AGMA 1010, Appearance of Gear Teeth – Terminology of Wear and Failure
High Speed Units

ANSI/AGMA 6011 Specification for High Speed Helical Gear Units
Inspection and Tolerances

AGMA 905 Inspection of Molded Plastic Gears
AGMA 915-2 Inspection Practices – Part 2: Double Flank Radial Composite Measurements
AGMA 915-3 Inspection Practices – Gear Blanks, Shaft Center Distance and Parallelism
AGMA 943-A22 Tolerances for Spur and Helical Racks
AGMA ISO 10064-1 Code of Inspection Practice – Part 1: Measurement of Cylindrical Gear Tooth Flanks
ANSI/AGMA 1102 Tolerance Specification for Gear Hobs
ANSI/AGMA 1104 Tolerance Specification for Shaper Cutters
ANSI/AGMA 1107 Tolerance for Specification for Form Milling Cutters
ANSI/AGMA 2002 Tooth Thickness Specification and Measurement
ANSI/AGMA 2011 Cylindrical Wormgearing Tolerance and Inspection Methods
ANSI/AGMA 2111 Cylindrical Wormgearing Tolerance and Inspection Methods (Metric)
ANSI/AGMA ISO 1328-1 Cylindrical Gears – ISO System of Flank Tolerance Classification – Part 1: Definitions
and Allowable Values of Deviations Relevant to Flanks of Gear Teeth
ANSI/AGMA ISO 1328-2 Cylindrical Gears — ISO System of Flank Tolerance Classification — Part 2:
Definitions and Allowable Values of Double Flank Radial Composite Deviations
ANSI/AGMA ISO 14104 Gears – Surface Temper Etch Inspection After Grinding, Chemical Method
ANSI/AGMA ISO 17485 Bevel Gears – ISO System of Accuracy
Lubrication
AGMA 955 Guidance for Industrial Gear Lubrication
ANSI/AGMA 9005 Industrial Gear Lubrication
AGMA ISO 18792-A19 Lubrication of industrial gear drives
Materials
AGMA 920 Materials for Plastic Gears
AGMA 923 Metallurgical Specifications for Steel and Cast Iron Gearing
AGMA 938 Shot Peening of Gears
AGMA 939 Austempered Ductile Iron for Gears
ANSI/AGMA 2004 Gear Materials, Heat Treatment and Processing Manual
ANSI/AGMA 6033 Materials for Marine Propulsion Gearing

ANSI/AGMA 6133 Materials for Marine Propulsion Gearing (Metric)
Metric Usage
AGMA 904 Metric Usage
Mill Drives
ANSI/AGMA 6014 Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment
ANSI/AGMA 6015 Power Rating of Single and Double Helical Gearing for Rolling Mill Service
ANSI/AGMA 6114 Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment (Metric)
ANSI/AGMA 6115 Power Rating of Single and Double Helical Gearing for Rolling Mill Service (Metric Edition)
Nomenclature
AGMA 933 Basic Gear Geometry
ANSI/AGMA 1012 Gear Nomenclature, Definitions of Terms with Symbols
Plastics Gears
AGMA 905 Inspection of Molded Plastic Gears
AGMA 909 Specifications for Molded Plastic Gears
AGMA 920 Materials for Plastic Gears
AGMA 946 Test Methods for Plastic Gears
ANSI/AGMA 1006 Tooth Proportions for Plastic Gears
Powder Metallurgy Gears

AGMA 930 Calculated Bending Load Capacity of Powder Metallurgy (P/M) External Spur Gears
AGMA 942 Metallurgical Specifications for Powder Metallurgy, PM, Steel Gearing
AGMA 944-A19, Mechanisms of Powder Metal, PM, Gear Failures
ANSI/AGMA 6008 Specifications for Powder Metallurgy Gears
Proportions
ANSI/AGMA 1003 Tooth Proportions for Fine-Pitch Spur and Helical Gears
ANSI/AGMA 1103 Tooth Proportions for Fine-Pitch Spur and Helical Gears (Metric Edition)
ANSI/AGMA 1106 Tooth Proportions for Plastic Gears (Metric Edition)
Rating: Spur, Helical and Bevel Gears

AGMA 908 Information Sheet – Geometry Factors for Determining the Pitting Resistance and Bending
Strength of Spur, Helical and Herringbone Gear Teeth
AGMA 918 A Summary of Numerical Examples Demonstrating the Procedures for Calculating Geometry
Factors for Spur and Helical Gears
AGMA 925 Effect of Lubrication on Gear Surface Distress
AGMA 927 Load Distribution Factors – Analytical Methods for Cylindrical Gears
AGMA 932 Rating the Pitting Resistance and Bending Strength of Hypoid Gears
ANSI/AGMA 2001 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear
Teeth
ANSI/AGMA 2003 Rating the Pitting Resistance and Bending Strength of Generated Straight Bevel, ZEROL
Bevel, and Spiral Bevel Gear Teeth
ANSI/AGMA 2101 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear
Teeth (Metric Edition)
ANSI/AGMA 6032 Standard for Marine Gear Units: Rating and Application for Spur and Helical Gear Teeth

ANSI/AGMA 6132 Standard for Marine Gear Units: Rating and Application for Spur and Helical Gear Teeth
(Metric Edition)
Sound and Vibration

AGMA 914 Gear Sound Manual – Part I: Fundamentals of Sound as Related to Gears; Part II: Sources,
Specifications and Levels of Gear Sound; Part III: Gear Noise Control
ANSI/AGMA 6000 Specification for Measurement of Linear Vibration on Gear Units
ANSI/AGMA 6025 Sound for Enclosed Helical, Herringbone, and Spiral Bevel Gear Drives
Splines
AGMA 945-1 Splines – Design and Application
AGMA 945-2 Splines – Design and Application (Inch Edition)
Style Manual
AGMA 900 Style Manual for the Preparation of Standards and Editorial Manuals
Thermal
Vehicle
ANSI/AGMA 6002 Design Guide for Vehicle Spur and Helical Gears
ANSI/AGMA 6102 Design Guide for Vehicle Spur and Helical Gears (Metric)
Wind Turbine Units

ANSI/AGMA 6006 Standard for Design and Specification of Gearboxes for Wind Turbines
Wormgears
ANSI/AGMA 6034 Practice for Enclosed Cylindrical Wormgear Speed Reducers and Gearmotors
ANSI/AGMA 6035 Design, Rating and Application of Industrial Globoidal Wormgearing
ANSI/AGMA 6134 Practice for Enclosed Cylindrical Wormgear Speed Reducers and Gearmotors (Metric)
ANSI/AGMA 6135 Design, Rating and Application of Industrial Globoidal Wormgearing (Metric)

AGMA Standards and Information Sheets
Many standards require additional documents for their proper use. A list of these standards is normally
supplied after the scope, in the normative references section of a document. Be sure to inquire whether
the standard you need requires other documents listed herewith.
AGMA 900-K22 Style Manual for the Preparation of Standards, Information Sheets and Editorial Manuals
This information sheet is a compilation of the AGMA and ISO editorial style manuals. This document provides
guidelines for the way that the AGMA Brand is presented from both a graphic and language perspective in
publications of the Technical Division, specifically standards and information sheets. It is intended for use
ensuring multiple contributors create a clear and cohesive way that reflects the corporate style and ensures brand
consistency. These standards will be applied either for general use or individual publication. Revision of
AGMA 900-J20.
Pages: 34
AGMA 901-A92 A Rational Procedure for the Preliminary Design of Minimum Volume Gears
Presents a simple, closed-form procedure as a first step in the minimum volume spur and helical gearset design.
It Includes methods for selecting geometry and dimensions, considering maximum pitting resistance, bending
strength, and scuffing resistance, and methods for selecting profile shift. Reaffirmed April 2020.
ISBN: 1-55589-579-4 Pages: 37
AGMA 904-C96 Metric Usage

Serves as a guide in preparing AGMA metric standards. Reaffirmed January 2017.
ISBN: 1-55589-681-2 Pages: 20
AGMA 905-A17 Inspection of Molded Plastic Gears

Due to their specification, design, and manufacture, plastic gears have unique issues that can affect the
measurement methods and results obtained. This information sheet describes industry accepted practices to
inspect molded plastic gears. It identifies the unique characteristics of molded plastic gears that influence the
accuracy and/or repeatability of gear measurements.
ISBN: 1-55589-735-2 Pages: 84
AGMA 908-B89 Geometry Factors for Determining the Pitting Resistance and Bending Strength of Spur,
Helical and Herringbone Gear Teeth
Gives the equations for calculating the pitting resistance geometry factor, I, for external and internal spur and
helical gears, and the bending strength geometry factor, J, for external spur and helical gears that are generated
by rack-type tools (hobs, rack cutters or generating grinding wheels) or pinion-type tools (shaper cutters). Includes
charts which provide geometry factors, I and J, for a range of typical gear sets and tooth forms. Reaffirmed
November 11, 2020.
ISBN: 1-55589-525-5 Pages: 78
AGMA 909-A06 Specifications for Molded Plastic Gears

The objective of this information sheet is to inform the plastic gear designer of the importance to clearly and
thoroughly define the gear specifications to the plastic gear producer. It discusses the specifications for gear tooth
geometry, inspection, other gear features and manufacturing considerations for involute external and internal spur
and helical gears. Suggested data forms are provided in the annexes. Reaffirmed April 10, 2018.
ISBN: 1-55589-889-8 Pages: 25
AGMA 910-D12 Formats for Fine-Pitch Gear Specification Data

This information sheet consists of a series of printed forms for gear drawings that contain the appropriate data to
be tabulated by the gear designer for the gear manufacturer. It also includes a series of definitions of the various
tabulated items. Replaces AGMA 910-C90. Reaffirmed September 6, 2017.
ISBN: 1-55589-999-8 Pages: 32

AGMA 911-B21 Guidelines for Aerospace Gear Systems
This information sheet covers current gearbox design practices as they are applied to air vehicles and spacecraft.
The material included goes beyond the design of gear meshes and presents the broad spectrum of factors which
combine to produce a working gear system, whether it be a power gearbox or special purpose mechanism.
Although a variety of gear types, such as wormgears, face gears and various proprietary tooth forms are used in
aerospace applications, this document covers only spur, helical, and bevel gears. Replaces AGMA 911-A94.
ISBN: 978-1-64353-094-9 Pages: 140
AGMA 913-A98 Method for Specifying the Geometry of Spur and Helical Gears
Provides information to translate tooth thickness specifications which are expressed in terms of tooth thickness,
center distance or diameter into profile shift coefficients. It describes the effect that profile shift has on the
geometry and performance of gears. Annexes are provided which contain practical examples on the calculation of
tool proportions and profile shift. Reaffirmed May 2021.
ISBN: 1-55589-714-2 Pages: 25
AGMA 914-B04, Gear Sound Manual – Part I: Fundamentals of Sound as Related to Gears; Part II: Sources,
Specifications and Levels of Gear Sound; Part III: Gear Noise Control
This information sheet discusses how noise measurement and control depend upon the individual characteristics
of the prime mover, gear unit, and driven machine, as well as their combined effects in a particular acoustical
environment. It indicates certain areas that might require special attention. This document is a revision of AGMA
299.01 to include updated references and a discussion of Fast Fourier Transform analysis. Replaces
AGMA 299.01. Reaffirmed March 15, 2018.
ISBN: 1-55589-820-3 Pages: 37
AGMA 915-2-B20 Inspection Practices – Part 2: Double Flank Radial Composite Measurements
This information sheet discusses inspection of cylindrical involute gears using the radial (double flank) composite
method, with recommended practices detailed. Also included is a clause on runout and eccentricity measurement
methods. This information sheet is a supplement to the standard ANSI/AGMA 2015-2. It replaced AGMA ISO
10064-2 and replaces double flank composite measurement section of AGMA 2000-A88.
ISBN: 978-1-64353-067-3 Pages: 52
AGMA 915-3-A99 Inspection Practices – Part 3: Gear Blanks, Shaft Center Distance and Parallelism
Provides recommended numerical values relating to the inspection of gear blanks, shaft center distance and
parallelism of shaft axes. Discussions include such topics as methods for defining datum axes on components;
the use of center holes and mounting surfaces during manufacturing and inspection; and, recommended values of
in-plane and out-of-plane deviations of shaft parallelism. Modified adoption of ISO/TR 10064-3:1996.
Reaffirmed October 2022.
ISBN: 1-55589-738-3 Pages: 9
AGMA 916-A19 Face Gears with Intersecting Perpendicular Axes

Describes design calculations for spur pinions and face gears that intersect with perpendicular axes. The
procedure described in this document will result in a face gear tooth geometry that is defined by the generating
action of a reciprocating spur gear cutter which incorporates certain essential features of the mating pinion. The
method described applies to all modules and profile angles.
ISBN: 978-1-64353-038-3 Pages: 93
AGMA 917-B97 Design Manual for Parallel Shaft Fine-Pitch Gearing

Provides guidance for the design of spur and helical gearing of 20 through 120 diametral pitch including internal
and rack forms. Manual contains such specialized subjects as inspection, lubrication, gear load calculation
methods, materials, including a wide variety of plastics. Replaces AGMA 370.01. Reaffirmed August 2022.
ISBN: 1-55589-694-4 Pages: 84

AGMA 918-A93 A Summary of Numerical Examples Demonstrating the Procedures for Calculating Geometry
Factors for Spur and Helical Gears
Provides numerical examples for calculating the pitting resistance geometry factor, I, and bending strength
geometry factor, J, for typical gearsets that are generated by rack-type tools (hobs, rack cutters or generating
grinding wheels) or pinion-type tools (disk-type shaper cutters). Supplement to AGMA 908-B89. Reaffirmed
November 11, 2020.
ISBN: 1-55589-617-0 Pages: 42
AGMA 919-1-A14 Condition Monitoring and Diagnostics of Gear Units and Open Gears: Part 1 – Basics
The new information sheet provides basic overviews of key approaches to establishing a condition monitoring and
diagnostics program for open gearing and enclosed gear units. This information sheet attempts to inform the
reader of the common techniques used and parameters measured for condition monitoring of a gear unit allowing
the reader to build a program based on individual needs. Reaffirmed March 25, 2019
ISBN: 978-1-61481-087-2 Pages: 20
AGMA 920-B15 Materials for Plastic Gears

The purpose of this document is to aid the gear designer in understanding the unique physical, mechanical and
thermal behavior of plastic materials. The use of plastic materials for gear applications has grown considerably
due to cost and performance issues. Growing markets include the automotive, business machine, and consumer-
related industries. Topics covered include general plastic material behavior, gear operating conditions, plastic
gear manufacturing, tests for gear related material properties, and typical plastic gear materials. There are no
quantitative details on material properties or any comparative evaluations of plastic types. Such specific
information is left to be provided by material suppliers and gear manufacturers. Revision of AGMA 920-A01.
Reaffirmed June 2, 2020
ISBN: 1-55589-048-3 Pages: 50
AGMA 922-A96 Load Classification and Service Factors for Flexible Couplings
This Information Sheet provides load classifications and related service factors that are frequently used for various
flexible coupling applications. Typical applications using smooth prime movers and special considerations
involving unusual or more severe loading are discussed. Replaces AGMA 514.02. Reaffirmed April 2020.
ISBN: 1-55589-680-4 Pages: 6
AGMA 923-C22 Metallurgical Specifications for Steel and Cast Iron Gearing
This document identifies metallurgical quality characteristics which are important to the performance of steel
gearing. The AGMA gear rating standards identify performance levels of gearing by heat treatment method and
grade number. For each heat treatment method and AGMA grade number, acceptance criteria are given for
various metallurgical characteristics identified in this document. Revision of AGMA 923-B05.
ISBN: 978-1-64353-119-9 Pages: 56
AGMA 925-B22 Effect of Tribology and Lubrication on Gear Surface Distress

AGMA 925-B22 covers lubricant-related damage modes in gear teeth. Various methods of gear surface distress
are included, such as scuffing and wear, and micro- and macropitting. This document contains additional
information about lubricant viscometric data, Dudley’s regimes of lubrication theory, surface roughness
measurements, EHD theory, FZG lubricant test rigs, Gaussian theory, flow charts, and example calculations.
Replaces AGMA 925-A03.
ISBN: 978-1-64353-116-8 Pages: 113
AGMA 926-C99 Recommended Practice for Carburized Aerospace Gearing

Establishes recommended practices for material case and core properties, microstructure and processing
procedures for carburized AISI 9310 aerospace gears. This document is not intended to be a practice for any
gears other than those applied to aerospace. Replaces AGMA 246.02a. Reaffirmed October 20, 2017.
ISBN: 1-55589-758-4 Pages: 9
AGMA 927-A01 Load Distribution Factors – Analytical Methods for Cylindrical Gears
Describes an analytical procedure for the calculation of face load distribution factor. The iterative solution that is
described is compatible with the definitions of the term face load distribution of AGMA standards and longitudinal
load distribution of the ISO standards. The procedure is easily programmable and flow charts of the calculation
scheme, as well as examples from typical software are presented. Supplement to ANSI/AGMA 2001-D04.
Reaffirmed January 30, 2018.
ISBN: 1-55589-779-7 Pages: 31

AGMA 929-B22 Calculation of Bevel Gear Top Land, Slot Widths and Cutter Edge Radii
This information sheet supplements ANSI/AGMA ISO 23509-A08 with calculations for bevel gear top land and
guidance for selection of cutter edge radius for determination of tooth geometry. It integrates various publications
with modifications to include face hobbing. It adds top land calculations for non-generated manufacturing
methods. It is intended to provide assistance in completing the calculations requiring determination of top lands
and cutter edge radii for gear capacity in accordance with ANSI/AGMA 2003-C10. Revision of AGMA 929-A06.
ISBN: 978-1-64353-120-5 Pages: 71
AGMA 930-A05 Calculated Bending Load Capacity of Powder Metallurgy (P/M) External Spur Gears
This information sheet describes a procedure for calculating the load capacity of a pair of powder metallurgy
external spur gears based on tooth bending strength. Two types of loading are considered: 1) repeated loading
over many cycles; and 2) occasional peak loading. It also describes an essentially reverse procedure for
establishing an initial design from specified applied loads. As part of the load capacity calculations, there is a
detailed analysis of the gear teeth geometry, including tooth profiles and various fillets. Reaffirmed August 2022.
ISBN: 1-55589-845-9 Pages: 78
AGMA 932-A05 Rating the Pitting Resistance and Bending Strength of Hypoid Gears
This information sheet provides a method by which different hypoid gear designs can be compared. The formulas
are intended to establish a uniformly acceptable method for calculating the pitting resistance and bending strength
capacity of both curved and skewed tooth hypoid gears. They apply equally to tapered depth and uniform depth
teeth. Annexes contain graphs for geometry factors and a sample calculation to assist the user. Supplement to
ANSI/AGMA 2003-B97. Reaffirmed February 3, 2011.
ISBN: 1-55589-869-6 Pages: 18
AGMA 933-B03 Basic Gear Geometry

This information sheet illustrates important geometrical relationships which provide a sound basis for a thoroughly
logical and comprehensive system of gear geometry. Replaces AGMA 115.01. Reaffirmed February 2022.
ISBN: 1-55589-814-9 Pages: 18
AGMA 935-A05 Recommendations Relative to the Evaluation of Radial Composite Gear Double Flank Testers
The condition and alignment of gear measuring instruments can greatly influence the measurement of product
gears. This information sheet provides qualification procedures for double flank testers that are used for the
evaluation of radial composite deviations of gears. It discusses guidelines for alignment of double flank tester
elements such as centers, ways, probe systems, etc. It also covers the application of artifacts to determine
instrument accuracy. Supplement to standard ANSI/AGMA 2116-A05. Reaffirmed April 2020.
ISBN: 1-55589-872-6 Pages: 11
AGMA 937-A12 Aerospace Bevel Gears

This information sheet covers aerospace bevel gears for power, accessory and actuation applications. It provides
additional information on the design, manufacturing and quality control unique to the aerospace environment. The
new information sheet was developed to fill the void following the withdrawal of AGMA 431.01. It expands the
scope to include all applications of aerospace bevel gearing. Reaffirmed August 2022.
ISBN: 1-61481-030-8 Pages: 142
AGMA 938-A05 Shot Peening of Gears

This information sheet provides a tool for gear designers interested in the residual compressive stress properties
produced by shot peening and its relationship to gearing. It also discusses shot media materials, delivery methods
and process controls. Reaffirmed September 19, 2017
ISBN: 1-55589-847-5 Pages: 14
AGMA 939-A07 Austempered Ductile Iron for Gears

This information sheet gives the background and basic guidelines to consider the feasibility of austempered
ductile iron (ADI) for gear applications. It contains experimental, experiential and anecdotal information to assist in
the specification, purchase and manufacture of ADI components. The metallurgy of ADI, relevant factors in its
production, allowable stress numbers, and stress cycle curves are reviewed. It also has references, relevant
standards, and evaluation methods used in the manufacture of ADI components. Reaffirmed January 30, 2018.
ISBN: 1-55589-901-1 Pages: 10

AGMA 940-A09 Double Helical Epicyclic Gear Units
This information sheet addresses epicyclic gear drives which utilize double helical type gearing on the planetary
elements. It is intended to be a supplement to and used in conjunction with ANSI/AGMA 6123-B06, Design
Manual for Enclosed Epicyclic Gear Dives. It covers only those topics which are unique to double helical gear
arrangements in epicyclic gear drives. Reaffirmed August 2022.
ISBN: 1-55589-953-0 Pages: 28
AGMA 942-A12 Metallurgical Specifications for Powder Metallurgy, PM, Steel Gearing
This information sheet recommends powder metallurgy, PM, steel materials and metallurgical quality
characteristics for use in specifying PM gearing. It identifies specifications and requirements for various PM steel
materials for as-sintered, through hardened or sinter hardened, carburized case hardened, and induction
hardened gearing. Requirements are coded by process and class number, the latter based on the density of the
PM gear teeth. Characteristics covered include material composition, density, sinter processing (conventional,
high temperature and sinter hardening), secondary heat treatments and post heat treatment processing, and their
associated inspections. Reaffirmed August 2022.
ISBN: 1-61481-031-5 Pages: 17
AGMA 943-A22 Tolerances for Spur and Helical Racks

This information sheet establishes a tolerance classification system relevant to manufacturing and conformity
assessment of tooth flanks of a single piece spur or helical rack. It specifies definitions for rack flank tolerance
terms, the structure of the flank tolerance class system, and allowable values.
ISBN: 978-1-64353-117-5 Pages: 22
AGMA 944-A19 Mechanisms of Powder Metal, PM, Gear Failures

This information sheet describes many of the ways in which powder metal, PM, gear teeth can fail and
recommends methods for reducing PM gear failures. It provides basic guidance for those attempting to analyze
PM gear failures. The information sheet should be used in conjunction with ANSI/AGMA 1010 in which the gear
tooth failure modes are defined. Similar definitions can also be found in ISO 10825 [1]. Although these standards
are primarily focused on steel parts, they help investigators understand failures and investigate remedies.
ISBN: 978-1-64353-036-9 Pages: 30
AGMA 945-1-B20 Splines – Design and Application

This information sheet covers parallel straight sided and involute splines. It provides information relating to
geometry, fit types, materials, manufacturing, rating, inspection, lubrication, and failure of splined elements.
Revision of AGMA 945-A18
ISBN: 978-1-64353-076-5 Pages: 79
AGMA 945-2-B20 Splines – Design and Application (Inch Edition)

This information sheet covers parallel straight sided and involute splines. It provides information relating to
geometry, fit types, materials, manufacturing, rating, inspection, lubrication, and failure of splined elements. For
metric based splines, see AGMA 945-1-B20.
ISBN: 978-1-64353-077-2 Pages: 79
AGMA 946-A21 Test Methods for Plastic Gears

This information sheet describes test methods and recommended documentation practices for determining load
carrying capacity and wear performance of plastic gears. It describes test methods for plastic gears related to
dynamic testing where two gears rotate against each other under controlled load and velocity, as well as static
testing where a gear is held stationary while a load is applied to one or more of the gear’s features, or pulsator
testing where the test gear is not rotating, but the load is pulsed repeatedly until fatigue failure occurs.
ISBN: 978-1-64353-091-8 Pages: 18
AGMA 955-A22 Guidance for Industrial Gear Lubrication

This information sheet provides lubrication guidelines for enclosed and open gearing installed in general industrial
power transmission applications. It is not intended to supplant specific instructions from the gear manufacturer.
ISBN: 978-1-64353-118-2 Pages: 73

AGMA ISO 10064-1-A21 Code of Inspection Practice – Part 1: Measurement of cylindrical gear tooth flanks
This information sheet provides a code of practice dealing with measurements on flanks of individual cylindrical
involute gears, i.e. with the measurement of pitch, profile, helix and tangential composite characteristics. It
describes measuring equipment, provides advice for gear measuring methods and for the analysis of
measurement results, and discusses the interpretation of results. Replaces AGMA 915-1-A02. Identical
adoption of ISO TR 10064-1:2019.
ISBN: 978-1-64353-089-5 Pages: 91
AGMA ISO 10064-5-A06 Code of Inspection Practice – Part 5: Recommendations Relative to Evaluation of
Gear Measuring Instruments
This information sheet provides methods and examples to support the implementation of ANSI/AGMA ISO 18653-
A06. It includes evaluation and calibration procedures for involute, helix, runout, and tooth thickness measurement
processes. Methods are given for the evaluation of condition and alignment of instrument elements such as
centers, guideways, probe systems, etc. Recommendations include statistical data evaluation procedures.
Guidance is given on the application of measurement processes to the inspection of product gears, including
fitness for use and the recommended limits of U95 uncertainty based on the accuracy tolerances of product gears
to be inspected. Many of its recommendations could be applied to the measurement of worms, worm wheels,
bevel gears and gear cutting tools. Replaces AGMA 931-A02. Reaffirmed November 1, 2012.
ISBN: 1-55589-881-5 Pages: 62
AGMA ISO 10064-6-A10 Code of Inspection Practice – Part 6: Bevel Gear Measurement Methods
This document provides information on measuring methods and practices of unassembled bevel and hypoid gears
and gear pairs. Tolerances are provided in ISO 17485:2006, for calculating the maximum values allowed by the
specific tolerance grade. These methods and practices are intended to promote uniform inspection procedures
which are accurate and repeatable to a degree compatible with the specified tolerance grade. Replaces
ANSI/AGMA 2009-B01. Reaffirmed November 1, 2012.
ISBN: 1-55589-994-3 Pages: 28
This information sheet utilizes an analytical heat balance model to provide a means of calculating the thermal
transmittable power for a single- or multi-stage gear drive lubricated with mineral oil. The calculation is based on
standard conditions of 25C maximum ambient temperature and 95C maximum oil sump temperature in a large
indoor space, but provides modifiers for other conditions. Differences from ISO/TR 14179-1 are: a) errors were
identified and corrected, b) text was added to clarify the calculation methods, and c) an illustrative example was
added to assist the reader. Modified adoption of ISO/TR 14179-1.
ISBN: 1-55589-821-1 Pages: 26
AGMA ISO 18792-A19 Lubrication of Industrial Gear Drives

This information sheet provides general guideline and source of information on lubricants and lubrication selection
for industrial drives
ISBN: 978-1-64353-039-0 Pages: 54
AGMA ISO 22849-A12 Design Recommendations for Bevel Gears

This information sheet provides information for the application of bevel and hypoid gears using the geometry in
ANSI/AGMA ISO 23509, the capacity as determined by ISO 10300 (all parts), or ANSI/AGMA 2003-C10 and
AGMA 932-A05, and the tolerances in ANSI/AGMA ISO 17485. This information sheet provides additional
information on the application, manufacturing, strength and efficiency of bevel gears for consideration in the
design stage of a new bevel gear set. Replaces ANSI/AGMA 2005-D03.
ISBN: 1-61481-029-2 Pages: 40
ANSI/AGMA 1003-H07 Tooth Proportions for Fine-Pitch Spur and Helical Gears
Tooth proportions for fine-pitch gearing are similar to those of coarse pitch gearing except in the matter of
clearance. This standard is applicable to external spur and helical gears with diametral pitch of 20 through
120 and a profile angle of 20 degrees. It provides a system of enlarged pinions which use the involute form above
5 degrees of roll. Data on 14-1/2 and 25-degree profile angle systems, and a discussion of enlargement and tooth
thicknesses are provided in annexes. In addition, it addresses, in a new annex, an analysis of comparative
systems of selecting tooth thicknesses of pinions. Revision of ANSI/AGMA 1003-G93. Reaffirmed February 6,
2020.
ISBN: 1-55589-902-8 Pages: 25

ANSI/AGMA 1006-A97 Tooth Proportions for Plastic Gears
Presents a new basic rack, AGMA PT, which, with its full round fillet, may be preferred in many applications of
gears made from plastic materials. It contains a description, with equations and sample calculations, of how the
proportions of a spur or helical gear may be derived from the design tooth thickness and the basic rack data. In
several annexes, there are discussions of possible variations from the basic rack and also a procedure for
defining tooth proportions without using the basic rack concept. Reaffirmed March 2023.
ISBN: 1-55589-684-7 Pages: 47
ANSI/AGMA 1010-F14 Appearance of Gear Teeth – Terminology of Wear and Failure

This standard provides nomenclature for general modes of gear tooth wear and failure. It classifies, identifies and
describes the most common types of failure and provides information which will, in many cases, enable the user
to identify failure modes and evaluate the degree or progression of wear. Revision of ANSI/AGMA 1010-E95.
Reaffirmed February 6, 2020.
ISBN: 1-61481-089-6 Pages: 81
ANSI/AGMA 1012-G05 Gear Nomenclature, Definitions of Terms with Symbols

This standard lists terms and their definitions with symbols for gear nomenclature. Revision of ANSI/AGMA
1012-F90. Reaffirmed March 2011.
ISBN: 1-55589-846-7 Pages: 89
ANSI/AGMA 1102-C19 Tolerance Specification for Gear Hobs

The purpose of this standard is to provide specifications for nomenclature, dimensions, tolerances, and inspection
of gear hobs, and thereby establish a basis for mutual understanding in this respect in the use and manufacture of
these tools. Revision of ANSI/AGMA 1102-B13.
ISBN: 978-1-64353-070-3 Pages: 58
ANSI/AGMA 1103-H07 Tooth Proportions for Fine-Pitch Spur and Helical Gears (Metric Edition)
Tooth proportions for fine-pitch gearing are similar to those of coarse pitch gearing except in the matter of
clearance. This standard is applicable to external spur and helical gears with diametral pitch of 1.25 through
0.2 and a profile angle of 20 degrees. It provides a system of enlarged pinions which use the involute form above
5 degrees of roll. Data on 14-1/2 and 25-degree profile angle systems, and a discussion of enlargement and tooth
thicknesses are provided in annexes. In addition, it addresses, in a new annex, an analysis of comparative
systems of selecting tooth thicknesses of pinions. Metric version of ANSI/AGMA 1003-H07. Reaffirmed
February 6, 2020.
ISBN: 1-55589-903-5 Pages: 25
ANSI/AGMA 1104-A09 Tolerance Specification for Shaper Cutters

The purpose of this standard is to provide specifications for nomenclature, dimensions, tolerances, and inspection
of shaper cutters, and thereby establish a basis for mutual understanding in this respect in the use and
manufacture of these tools. Reaffirmed November 19, 2020.
ISBN: 1-55589-974-5 Pages: 54
ANSI/AGMA 1106-A97 Tooth Proportions for Plastic Gears

Presents a new basic rack, AGMA PT, which, with its full round fillet, may be preferred in many applications of
gears made from plastic materials. It contains a description, with equations and sample calculations, of how the
proportions of a spur or helical gear may be derived from the design tooth thickness and the basic rack data. In
several annexes, there are discussions of possible variations from the basic rack and also a procedure for
defining tooth proportions without using the basic rack concept. Metric edition of ANSI/AGMA 1006-A97.
Reaffirmed March 2023.
ISBN: 1-55589-685-5 Pages: 47
ANSI/AGMA 1107-A19 Tolerance Specification for Form Milling Cutters

This standard provides specifications for nomenclature, dimensions, tolerances and inspection for form milling
cutters. Included in these are involute type, straight sided for rack or worm thread generation, form relieved,
indexable carbide insert (ICI), and special form. This standard establishes a basis for understanding the use and
manufacture of these form types of milling cutters.
ISBN: 978-1-64353-071-0 Pages: 52

ANSI/AGMA 2001-D04 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical
Gear Teeth
Presents a comprehensive method for rating the pitting resistance and bending strength of spur and helical
involute gear pairs. Contains detailed discussions of factors influencing gear survival and calculation methods.
Revisions reflected in this version include incorporating the latest AGMA accuracy standard (ANSI/AGMA 2015-1-
A01) into the determination of dynamic factor and change to the relationship between service factor and stress
cycle factor. Revision of ANSI/AGMA 2001-C95. Reaffirmed March 2016.
ISBN: 1-55589-839-4 Pages: 56
ANSI/AGMA 2002-D19, Tooth Thickness and Backlash Measurement of Cylindrical Involute Gearing
Establishes the procedures for determining the specification limits for tooth thickness of external and internal
cylindrical involute gearing. Includes equations and calculation procedures for the commonly used measuring
methods. A specific tooth thickness specification limit can be established from the design thickness or from
another tooth thickness measurement. The procedures can be used with an established design tooth thickness, or
with actual tooth thickness dimensions. The effect of tooth geometric quality variations on tooth thickness
dimensions is discussed. Calculations for backlash are included, and are based on the specified tooth thickness,
center distance, and tolerances. Revision of ANSI/AGMA 2002-B88.
ISBN: 978-1-64353-068-0 Pages: 145
ANSI/AGMA 2003-D19 Rating the Pitting Resistance and Bending Strength of Generated Straight Bevel, Zerol
Bevel and Spiral Bevel Gear Teeth
This standard specifies a method for rating the pitting resistance and bending strength of generated straight bevel,
zerol bevel and spiral bevel gear teeth. A detailed discussion of factors influencing gear survival and a calculation
method are provided. Revision of ANSI/AGMA 2003-C10.
ISBN: 978-1-64353-037-6 Pages: 99
ANSI/AGMA 2004-C08 Gear Materials, Heat Treatment and Processing Manual

This standard provides information pertaining to ferrous and nonferrous materials used in gearing. Factors in
material selection, including material forms, properties, and associated processing and heat treatments are
discussed. Manufacturing procedures to prepare materials for machining and final heat treatment are included.
Heat treating procedures used for gearing are covered in detail, including process description, product
specifications, process controls, and characteristics of heat treated gearing. Post-heat treatment processes to
meet gearing requirements are discussed. Product inspection methods and documentation are covered. Term
definitions, test methods, distortion and residual stress, sources for additional information and bibliography are
included. Revision of ANSI/AGMA 2004-B89. Reaffirmed February 6, 2020.
ISBN: 1-55589-904-2 Pages: 68
ANSI/AGMA 2008-D11 Assembling Bevel Gears

This Standard was prepared for the assembly man in the factory and for the service man in the field. Each
definition, explanation, and instruction is directed toward the physical appearance of the gears as they are
inspected and assembled by these personnel. The definitions are simple. The explanations are thorough. An
Annex provides detailed instructions on performing contact pattern checks. Reaffirmed November 2021.
ISBN: 1-55589-998-1 Pages: 49
ANSI/AGMA 2011-B14 Cylindrical Wormgearing Tolerance and Inspection Methods

This standard describes and defines variations that may occur in unassembled wormgearing. It displays
measuring methods and practices, giving suitable warnings if a preferred probe cannot be used. The applicability
of single or double flank composite testing is discussed, using a reference gear. Tooth thickness measurement is
shown using direct measurement as well as the use of measurements over wires or pins. Equations for the
maximum variations are given for the stated ranges, as a function of size, pitch and tolerance grade. Revision of
ANSI/AGMA 2011-A98. Reaffirmed December 17, 2019.
ISBN: 1-61481-090-2 Pages 51

ANSI/AGMA 2101-D04 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical
Gear Teeth (Metric Edition)
Presents a comprehensive method for rating the pitting resistance and bending strength of spur and helical
involute gear pairs. Contains detailed discussions of factors influencing gear survival and calculation methods.
Revisions reflected in this version include incorporating the latest AGMA accuracy standard (ANSI/AGMA 2015-1-
A01) into the determination of dynamic factor and change to the relationship between service factor and stress
cycle factor. Revision of ANSI/AGMA 2101-C95. Reaffirmed March 2016.
ISBN: 1-55589-840-8 Pages: 56
ANSI/AGMA 2111-A98 Cylindrical Wormgearing Tolerance and Inspection Methods

Establishes a classification system for the geometrical accuracy specification of wormgearing. It also provides
uniform measurement procedures including discussions on single and double flank composite testing and tooth
thickness measurements. The standard establishes ten accuracy grades, W3 through W12, based on the relative
effect of geometrical errors on conjugate action for wormgear sets. Metric edition of ANSI/AGMA 2011-A98.
Reaffirmed November 20, 2020.
ISBN: 1-55589-717-7 Pages: 43
ANSI/AGMA 2116-A05 Evaluation of Double Flank Testers for Radial Composite Measurement of Gears
This standard provides the evaluation criteria for double flank testers. Recommended artifact sizes and geometry
are provided along with measurement system conditions. Annexes contain methods for estimating calibration
uncertainty and specifying artifact. Reaffirmed February 2, 2017.
ISBN: 1-55589-871-8 Pages: 9
ANSI/AGMA 6000-C20 Specification for Measurement of Linear Vibration on Gear Units

This standard presents a method for the measurement of linear vibrations on a gear unit. Instrumentation,
measuring methods, test procedures and discrete frequency vibration limits are recommended for acceptance
testing to confirm integrity. An annex which lists system effects on gear unit vibration and responsibility is also
provided. Revision of ANSI/AGMA 6000-B96.
ISBN: 1-55589-666-9 Pages: 21
ANSI/AGMA 6001-F19 Design and Selection of Components for Enclosed Gear Drives
This standard outlines the basic practices for the design and selection of components, other than gearing, for use
in commercial and industrial enclosed gear drives. Fundamental equations provide for the proper sizing of shafts,
keys, and fasteners based on stated allowable stresses. Other components are discussed in a manner to provide
an awareness of their function or specific requirements. This standard applies to the following types of commercial
and industrial enclosed gear drives, individually or in combination: spur, helical, herringbone, bevel and worm.
Revision of ANSI/AGMA 6001-E08.
ISBN: 978-1-64353-035-2 Pages: 66
ANSI/AGMA 6002-D20 Design Guide for Vehicle Spur and Helical Gears
This standard provides information on the design of spur and helical vehicle power transmission gears. Included
are considerations for design, material and heat treatment, lubrication, determination of load capacity, mounting
features, and typical design problems. Revision of ANSI/AGMA 6002-C15.
ISBN: 978-1-64353-074-1 Pages: 65
ANSI/AGMA 6006-B20 Standard for Design and Specification of Gearboxes for Wind Turbines
This standard is intended to apply to wind turbine gearboxes. It provides information for specifying, selecting,
designing, manufacturing, testing, procuring, operating and maintaining reliable speed increasing gearboxes for
wind turbine generator system service.
Annex information is supplied on wind turbine architecture, wind turbine load description, quality assurance,
operation and maintenance, minimum purchaser gearbox manufacturer ordering data, lubrication selection and
monitoring, determination of an application factor from a load spectrum using the equivalent torque, and bearing
stress calculations. Revision of ANSI/AGMA/AWEA 6006-A03.
ISBN: 978-1-64353-073-4 Pages: 46

ANSI/AGMA 6008-A98 Specifications for Powder Metallurgy Gears
Defines the minimum detailed information to be included in the powder metallurgy gear specifications submitted
by the gear purchaser to the gear producer. Specifications on gear tooth geometry are described in detail for
external spur and helical gears and for straight bevel gears. In addition, there are discussions on specifications for
gear drawings and gear material data. The standard applies to gears made by the conventional P/M process
consisting of compaction followed by sintering and, in some cases, by post sintering treatments. Reaffirmed
December 14, 2017.
ISBN: 1-55589-713-4 Pages: 17
ANSI/AGMA 6011-J14 Specification for High Speed Helical Gear Units

This standard includes design, lubrication, bearings, testing and rating for single and double helical external tooth,
parallel shaft speed reducers or increasers. Units covered include those operating with at least one stage having a
pitch line velocity equal to or greater than 35 meters per second or rotational speeds greater than 4500 rpm and
other stages having pitch line velocities equal to or greater than 8 meters per second. Revision of ANSI/AGMA
6011-I03. Reaffirmed December 19, 2019.
ISBN: 1-61481-088-9 Pages: 69
ANSI/AGMA 6013-B16 Standard for Industrial Enclosed Gear Drives

This standard includes design, rating, lubrication, testing, and selection information for enclosed gear drives,
including foot mounted, shaft mounted, screw conveyor drives, and gearmotors. These drives may include spur,
helical, herringbone, double helical, or bevel gearing in single or multistage arrangements as either parallel,
concentric, or right-angle configurations. Revision of ANSI/AGMA 6013-A06. Reaffirmed November 2021.
NOTE: ANSI/AGMA 6013-B16 has an errata included at the end of the document.
ISBN: 978-1-55589-049-0 Pages: 86
ANSI/AGMA 6014-B15 Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment
This standard specifies a method for rating the pitting resistance and bending strength of open or semi-enclosed
gearing for use on cylindrical shell and trunnion supported equipment such as grinding mills, kilns, coolers, and
dryers. This includes spur, self-aligning spur, single helical, double helical, and herringbone gears made from
steel, ductile iron, and austempered ductile iron. Annexes cover installation, alignment, maintenance, combination
drives, and lubrication. Revision of ANSI/AGMA 6014-A06. Reaffirmed December 4, 2020.
ISBN: 1-55589-045-2 Pages: 82
ANSI/AGMA 6015-A13 Power Rating of Single and Double Helical Gearing for Rolling Mill Service
This Standard provides a method for determining the power rating of gear sets used in main mill drives, pinion
stands, and combination units used for the reduction of material size in metal rolling mills. Applications include,
but are not limited to, hot mills and cold mills, roughing and finishing stands: reducing, increasing, and 1:1 ratio
sets. Auxiliary drives, including drives listed in ANSI/AGMA 6013-A06, such as bridles, coilers, uncoilers, edge
trimmers, flatteners, loopers (accumulators), pinch rolls, scrap choppers, shears, and slitters are not covered by
this document. This standard includes a method by which different gear tooth designs can be rated and compared
at extended life cycles typical for these applications, up to 175 000 hours. Reaffirmed December 17, 2018.
ISBN: 1-61481-056-8 Pages: 67
ANSI/AGMA 6022-D19 Standard for Design Manual for Cylindrical Wormgearing

Covers the design of fine and coarse pitch cylindrical wormgearing operating at right angles and primarily made
as gear sets to be incorporated into other machines and mechanisms. Many of the design procedures are also
incorporated in enclosed drives.
ISBN: 1-55589-041-5 Pages: 44
NOTE: ANSI/AGMA 6022-D19 has an errata included at the end of the document
ANSI/AGMA 6025-E19 Sound for Enclosed Helical, Herringbone and Spiral Bevel Gear Drives
Describes a recommended method of acceptance testing and reporting of the sound pressure levels generated by
a gear speed reducer or increaser when tested at the manufacturer’s facility. The results obtained through the use
of this standard should represent only the sound of the gear unit, as other system influences, such as prime
mover or driven equipment are minimized. Annexes to the standard present sound power measurement methods
for use when required by specific contract provisions between the manufacturer and purchaser. Revision of
ANSI/AGMA 6025-D98.
ISBN: 978-1-64353-033-8 Pages: 32

ANSI/AGMA 6032-B13 Standard for Marine Gear Units: Rating and Application for Spur and Helical
Gear Teeth
This document considers rating practices for marine main propulsion, power take-off and auxiliary propulsion
service. Revision of ANSI/AGMA 6032-A94. Reaffirmed December 14, 2018.
ISBN: 1-61481-084-1 Pages: 52
ANSI/AGMA 6033-C08 Materials for Marine Propulsion Gearing

This standard identifies commonly used alloy steels, heat treatments and inspection requirements for through
hardened and surface hardened gearing for main propulsion marine service over 1500 hp. Forged and hot rolled
alloy steel bar stock are specified to two metallurgical quality grades (1 and 2) according to cleanliness and test
requirements. Cast steel gearing is specified to a single metallurgical quality level. Mechanical, metallurgical and
nondestructive test requirements are provided for various heat treatment processes and metallurgical quality
grades of gearing. Revision of ANSI/AGMA 6033-B98. Reaffirmed February 7, 2020.
ISBN: 1-55589-929-5 Pages: 34
ANSI/AGMA 6034-C21 Practice for Enclosed Cylindrical Wormgear Speed Reducers and Gearmotors
This standard gives a method for rating and design of specific enclosed cylindrical wormgear reducers and gear
motors at speeds not greater than 3600 rpm or mesh sliding velocities not more than 6000 ft/min. It contains
power, torque and efficiency equations with guidance on component design, thermal capacity, service factor
selection, lubrication, and self-locking features of wormgears. Annexes are supplied on service factors, user
recommendations. Replaces ANSI/AGMA 6034-B92.
ISBN: 978-1-64353-092-5 Pages: 43
ANSI/AGMA 6035-A02 Design, Rating and Application of Industrial Globoidal Wormgearing

This standard provides guidelines for the design, rating and application of globoidal wormgearing mounted at a
90-degree angle. Specific definitions for globoidal wormgearing terms are presented, along with formulas for
determining the geometric sizes of the major features for the worm and gear. Design considerations, design
procedures, gear blanks and self-locking conditions are also discussed. Procedures for rating the load capacity of
globoidal wormgearing are included. Replaces ANSI/AGMA 6017-E86 and ANSI/AGMA 6030-C87. Reaffirmed
May 2019.
ISBN: 1-55589-792-4 Pages: 45
ANSI/AGMA 6101-F19 Design and Selection of Components for Enclosed Gear Drives (Metric Edition)
This standard outlines the basic practices for the design and selection of components, other than gearing, for use
in commercial and industrial enclosed gear drives. Fundamental equations provide for the proper sizing of shafts,
keys, and fasteners based on stated allowable stresses. Other components are discussed in a manner to provide
an awareness of their function or specific requirements. This standard applies to the following types of commercial
and industrial enclosed gear drives, individually or in combination: spur, helical, herringbone, bevel and worm.
Metric Edition of ANSI/AGMA 6101-E08.
ISBN: 978-1-64353-034-5 Pages: 63
ANSI/AGMA 6102-D20 Design Guide for Vehicle Spur and Helical Gears (Metric Edition)
This standard provides information on the design of spur and helical vehicle power transmission gears. Included
are considerations for design, material and heat treatment, lubrication, determination of load capacity, mounting
features, and typical design problems. Metric edition of ANSI/AGMA 6002-D20.
ISBN: 978-1-64353-075-8 Pages: 65
ANSI/AGMA 6113-B16 Standard for Industrial Enclosed Gear Drives (Metric Edition)
This standard includes design, rating, lubrication, testing, and selection information for enclosed gear drives,
including foot mounted, shaft mounted, screw conveyor drives, and gearmotors. These drives may include spur,
helical, herringbone, double helical, or bevel gearing in single or multistage arrangements as either parallel,
concentric, or right angle configurations. Metric version of ANSI/AGMA 6013-B16. Replaces ANSI/AGMA 6113-
A06. Reaffirmed November 2021.
NOTE: ANSI/AGMA 6113-B16 has an errata included at the end of the document.
ISBN: 978-1-55589-051-3 Pages: 85

ANSI/AGMA 6114-B15 Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment
(Metric Edition)
This standard specifies a method for rating the pitting resistance and bending strength of open or semi-enclosed
gearing for use on cylindrical shell and trunnion supported equipment such as grinding mills, kilns, coolers, and
dryers. This includes spur, self-aligning spur, single helical, double helical, and herringbone gears made from
steel, ductile iron, and austempered ductile iron. Annexes cover installation, alignment, maintenance, combination
drives, and lubrication. Replaces 6114-A06. Metric edition of ANSI/AGMA 6014-B15. Reaffirmed December 4,
2020.
ISBN: 1-55589-047-6 Pages: 82
ANSI/AGMA 6115-A13 Power Rating of Single and Double Helical Gearing for Rolling Mill Service
(Metric Edition)
This Standard provides a method for determining the power rating of gear sets used in main mill drives, pinion
stands, and combination units used for the reduction of material size in metal rolling mills. Applications include,
but are not limited to, hot mills and cold mills, roughing and finishing stands: reducing, increasing, and 1:1 ratio
sets. Auxiliary drives, including drives listed in ANSI/AGMA 6113-A06, such as bridles, coilers, uncoilers, edge
trimmers, flatteners, loopers (accumulators), pinch rolls, scrap choppers, shears, and slitters are not covered by
this document. This standard includes a method by which different gear tooth designs can be rated and compared
at extended life cycles typical for these applications, up to 175 000 hours. Reaffirmed December 14, 2018.
ISBN: 1-61481-057-5 Pages: 67
ANSI/AGMA 6123-C16 Design Manual for Enclosed Epicyclic Gear Drives

This is a design manual for drives employing epicyclic gear arrangements. It includes descriptions of epicyclic
drives, nomenclature, application information and design guidelines with reference to other AGMA standards.
Replaces ANSI/AGMA 6123-B06. Reaffirmed October 2021.
ISBN: 1-55589-059-9 Pages: 136
NOTE: ANSI/AGMA 6123-C16 has an errata included at the end of the document.
ANSI/AGMA 6132-B13 Standard for Marine Gear Units: Rating and Application for Spur and Helical Gear
Teeth (Metric Edition)
This document considers rating practices for marine main propulsion, power take-off and auxiliary propulsion
service. Metric edition of ANSI/AGMA 6032-B13. Reaffirmed December 14, 2018.
ISBN: 1-61481-085-8 Pages: 52
ANSI/AGMA 6133-C08 Materials for Marine Propulsion Gearing

This standard identifies commonly used alloy steels, heat treatments and inspection requirements for through
hardened and surface hardened gearing for main propulsion marine service over 1500 hp. Forged and hot rolled
alloy steel bar stock are specified to two metallurgical quality grades (1 and 2) according to cleanliness and test
requirements. Cast steel gearing is specified to a single metallurgical quality level. Mechanical, metallurgical and
nondestructive test requirements are provided for various heat treatment processes and metallurgical quality
grades of gearing. Metric version of ANSI/AGMA 6033-C08. Reaffirmed February 7, 2020.
ISBN: 1-55589-930-1 Pages: 34
ANSI/AGMA 6134-C21 Practice for Enclosed Cylindrical Wormgear Speed Reducers and Gearmotors (Metric
Edition)
This standard gives a method for rating and design of specific enclosed cylindrical wormgear reducers and gear
motors at speeds not greater than 3600 rpm or mesh sliding velocities not more than 30 m/s. It contains power,
torque and efficiency equations with guidance on component design, thermal capacity, service factor selection,
lubrication, and self-locking features of wormgears. Annexes are supplied on service factors, user
recommendations. Metric version of ANSI/AGMA 6034-C21.
ISBN: 978-1-64353-093-2 Pages: 43

ANSI/AGMA 6135-A02 Design, Rating and Application of Industrial Globoidal Wormgearing (Metric Version)
This standard provides guidelines for the design, rating and application of globoidal wormgearing mounted at a
90-degree angle. Specific definitions for globoidal wormgearing terms are presented, along with formulas for
determining the geometric sizes of the major features for the worm and gear. Design considerations, design
procedures, gear blanks and self-locking conditions are also discussed. Procedures for rating the load capacity of
globoidal wormgearing are included. Replaces ANSI/AGMA 6017-E86 and ANSI/AGMA 6030-C87. Metric
edition of ANSI/AGMA 6035-A02. Reaffirmed May 2019.
ISBN: 1-55589-793-2 Pages: 45
ANSI/AGMA 9000-D11 Flexible Couplings – Potential Unbalance Classification

This standard defines classes of flexible coupling potential unbalance, one of which the user must select in order
to meet the needs of their system. The classes are established using weight and speed and system sensitivity to
arrive at a mass displacement value that defines the potential unbalance. The standard defines types of
unbalance, provides a method of selecting balance class, identifies contributors to potential unbalance, and
provides a method of determining potential coupling unbalance. The balance classes are derived from
consideration of the potential unbalance of the coupling. Reaffirmed January 2022.
ISBN: 1-55589-995-0 Pages: 69
ANSI/AGMA 9001-C18 Flexible Couplings – Lubrication

This standard provides information on lubrication of gear couplings, chain couplings and metallic grid couplings.
Types of lubricants and lubrication methods and practices are included. In addition, selection guides for grease
and oil lubrication are provided. Revision of ANSI/AGMA 9001-B97.
ISBN: 978-1-64353-003-1 Pages: 12
ANSI/AGMA 9002-C14 Bores and Keyways for Flexible Couplings (Inch Series)
This standard describes sizes and tolerances for straight and tapered bores and the associated keys and
keyways, as furnished in flexible couplings. The data in the standard considers commercially standard coupling
bores and keyways, not special coupling bores and keyways that may require special tolerances. Annexes
provide material on inspection methods and design practices for tapered shafts. Revision of ANSI/AGMA
9002-B04. Reaffirmed June 8, 2020.
ISBN: 1-61481-091-9 Pages: 28
ANSI/AGMA 9003-C17 Flexible Couplings – Keyless Fits

This standard presents information on design, dimensions, tolerances, inspection, mounting, removal, and
equipment that is in common use with keyless tapered and keyless straight (cylindrical) bore hubs for flexible
couplings. Revision of ANSI/AGMA 9003-B08. Reaffirmed October 2022. (Errata included)
ISBN: 978-1-64353-000-0 Pages: 21
ANSI/AGMA 9004-B08 Flexible Couplings – Mass Elastic Properties and Other Characteristics
This standard provides calculation methods related to mass elastic properties of flexible couplings. Properties
discussed include coupling mass, polar mass moment of inertia (WR2), center of gravity, axial stiffness, axial
natural frequency, lateral stiffness, lateral natural frequency, and torsional stiffness. Calculation examples are
provided in informative annexes. Revision of ANSI/AGMA 9004-A99. Reaffirmed April 2020.
ISBN: 1-55589-973-8 Pages: 33
ANSI/AGMA 9005-F16 Industrial Gear Lubrication

This standard provides lubrication guidelines for enclosed and open gearing installed in general industrial power
transmission applications. It is not intended to supplant specific instructions from the gear manufacturer. Revision
of ANSI/AGMA 9005-E02. Reaffirmed October 2021.
ISBN: 978-1-55589-052-0 Pages: 46
ANSI/AGMA 9006-A16 Flexible Couplings – Basis for Rating

This standard presents criteria and guidelines for the establishment of the basis for ratings of standard flexible
couplings. Due to the diversity of coupling types, details of design such as formulas and analysis used to derive
the stresses, etc. are often considered proprietary and are not considered in this standard. This standard is of
importance to coupling manufacturers, users and equipment designers for the proper selection, comparison and
application of flexible couplings. Reaffirmed January 2022.
ISBN: 978-1-55589-057-5 Pages: 18

ANSI/AGMA 9008-B00 Flexible Couplings – Gear Type – Flange Dimensions, Inch Series
Defines the North American industry practice for the interface dimensions of the sleeve and rigid hubs of both
shrouded and exposed bole, inch series, gear type couplings. Reaffirmed October 2022.
ISBN: 1-55589-736-3 Pages: 3
ANSI/AGMA 9009-E20 Flexible Couplings – Nomenclature for Flexible Couplings

This standard presents the nomenclature common to flexible couplings as used in mechanical power transmission
drives. It does not address nomenclature for flexible shafts, quill shafts, universal joints or devices that exhibit slip
such as clutches, fluid couplings, magnetic couplings or torque converters. The standard was prepared to reduce
the language barriers that arise between designers, manufacturers and users when attempting to designate or
describe various types of flexible couplings and their elements. Revision of ANSI/AGMA 9009-D02.
ISBN: 978-1-64353-078-9 Pages: 26
ANSI/AGMA 9103-C17 Flexible Couplings – Keyless Fits (Metric Edition)

This standard presents information on design, dimensions, tolerances, inspection, mounting, removal, and
equipment that is in common use with keyless tapered and keyless straight (cylindrical) bore hubs for flexible
couplings. Metric version of ANSI/AGMA 9003-C17. Reaffirmed October 2022. (Errata included)
ISBN: 978-1-64353-001-7 Pages: 22
ANSI/AGMA 9104-A06 Flexible Couplings – Mass Elastic Properties and Other Characteristics (Metric Edition)
This standard provides calculation methods related to mass elastic properties of flexible couplings. Properties
discussed include coupling mass, polar mass moment of inertia, center of gravity, axial stiffness, axial natural
frequency, lateral stiffness, lateral natural frequency, and torsional stiffness. Calculation examples are provided in
informative annexes. Metric edition of ANSI/AGMA 9004-A99. Reaffirmed October 2022.
ISBN: 1-55589-900-4 Pages: 32
ANSI/AGMA 9110-A11 Flexible Couplings – Potential Unbalance Classification (Metric Edition)

This metric standard defines classes of flexible coupling potential unbalance, one of which the user must select in
order to meet the needs of their system. The classes are established using mass and speed and system
sensitivity to arrive at a mass displacement value that defines the potential unbalance. The standard defines types
of unbalance, provides a method of selecting balance class, identifies contributors to potential unbalance, and
provides a method of determining potential coupling unbalance. The balance classes are derived from
consideration of the potential unbalance of the coupling. Metric edition of ANSI/AGMA 9000-D11. Reaffirmed
January 2022.
ISBN: 1-55589-996-7 Pages: 69
ANSI/AGMA 9112-B15 Bores and Keyways for Flexible Couplings (Metric Series)
This standard describes sizes and tolerances for straight and tapered bores and the associated keys and
keyways, as furnished in flexible couplings. The data in the standard considers commercially standard coupling
bores and keyways, not special coupling bores and keyways that may require special tolerances. Annexes
provide material on inspection methods and design practices for tapered shafts. Metric edition of ANSI/AGMA
9002-C14. Reaffirmed December 7, 2020
ISBN: 1-61481-092-6 Pages: 36
ANSI/AGMA ISO 1328-1-B14 Cylindrical gears – ISO system of flank tolerance classification – Part 1:
Definitions and allowable values of deviations relevant to flanks of gear teeth
This standard establishes a tolerance classification system relevant to manufacturing and conformity assessment
of tooth flanks of individual cylindrical involute gears. It specifies definitions for gear flank tolerance terms, the
structure of the flank tolerance class system, and allowable values. Replaces ANSI/AGMA 2015-1-A01.
ISBN: 1-61481-114-5 Pages: 47
ANSI/AGMA ISO 1328-2-A21 Cylindrical Gears — ISO System of Flank Tolerance Classification — Part 2:
Definitions and Allowable Values of Double Flank Radial Composite Deviations
This document establishes a gear tooth classification system relevant to double flank radial composite deviations
of individual cylindrical involute gears and sector gears. It provides formulae to calculate tolerances for individual
product gears when mated in double flank contact with a master gear. Identical to ISO 1328-2:2020.
ISBN: 978-1-64353-115-1 Pages: 26

ANSI/AGMA ISO 14104-A17 Gears – Surface Temper Etch Inspection After Grinding, Chemical Method
This document explains the materials and procedures necessary to determine, evaluate and describe localized
overheating on ground surfaces. A system to describe and classify the indications produced during this inspection
is included. However, specific acceptance or rejection criteria are not contained.
An industry-wide survey was conducted to establish common solutions in time that were acceptable to the
greatest number of users. The safety and environmental precautions were included therein for those not familiar
with storage, handling, use and disposal of concentrated acids, alkalis and solvents. These precautions, however,
do not supersede the latest applicable requirements. Replaces ANSI/AGMA 2007-C00
ISBN: 978-1-64353-032-1 Pages: 23
ANSI/AGMA ISO 17485-A08 Bevel Gears – ISO System of Accuracy

This standard establishes a classification system that can be used to communicate geometrical accuracy
specifications of unassembled bevel gears, hypoid gears, and gear pairs. It defines tooth accuracy terms,
specifies the structure of the gear accuracy grade system, and provides allowable values. The standard provides
the gear manufacturer and the gear buyer with a mutually advantageous reference for uniform tolerances. Ten
grades are defined, numbered 2 to 11 in order of decreasing precision. Equations for tolerances and their ranges
of validity are provided for bevel and hypoid gearing. Identical adoption of ISO 17485:2006. Replaces
ANSI/AGMA 2009-B01. Reaffirmed March 2014.
ISBN: 1-55589-926-4 Pages: 23
Supplemental Tables for ANSI/AGMA ISO 17485-A08 Bevel Gears – ISO System of Accuracy –
Tolerance Tables
This information sheet contains tolerance tables dealing with the measurements of bevel gear tooth flanks.
While the tables may be used to estimate the tolerance, the actual tolerances are provided in ANSI/AGMA
ISO 17485-A08.
ISBN: 1-55589-950-9 Pages: 39
ANSI/AGMA ISO 18653-A06 Gears – Evaluation of Instruments for the Measurement of Individual Gears
This International Standard specifies methods for the evaluation of measuring instruments used to measure
cylindrical gear involute, helix, pitch and runout. It includes instruments that measure runout directly or compute it
from index measurements. Of necessity, it includes the estimation of measurement uncertainty with the use of
calibrated gear artifacts. It also gives recommendations for the evaluation of tooth thickness measuring
instruments. The estimation of product gear measurement uncertainty is beyond its scope (see AGMA ISO 10064-
5-A06 for recommendations). This standard is an identical adoption of ISO 18653:2006. Replaces ANSI/AGMA
2010-A94, ANSI/AGMA 2110-A94, ANSI/AGMA 2113-A97 and ANSI/AGMA 2114-A98.
ISBN: 1-55589-882-3 Pages: 14
ANSI/AGMA ISO 23509-B17 Bevel and Hypoid Gear Geometry

This standard specifies the geometry of bevel gears. The term ‘bevel gears’ is used to mean straight, spiral, zerol
bevel and hypoid gear designs. If the text pertains to one or more, but not all, of these, the specific forms are
identified. This standard is intended for use by an experienced gear designer capable of selecting reasonable
values for the factors based on his/her knowledge and background. It is not intended for use by the engineering
public at large. Replaces ANSI/AGMA ISO 23509-A08.
ISBN: 978-1-64353-002-4 Pages: 143

ISO Standards, Technical Reports, and Technical Specifications by
ISO Technical Committee 60
Technical Committee 60 is responsible for the development of all international gear-related standards.
Many standards require additional documents for their proper use. A list of these standards is normally
supplied after the scope, in the normative references section of a document. Be sure to inquire whether
the standard you need requires other documents listed herein.
ISO 53:1998 Cylindrical gears for general and heavy engineering – Standard basic rack tooth profile
ISO 54:1996 Cylindrical gears for general engineering and for heavy engineering – Modules
ISO 677:1976 Straight bevel gears for general engineering and heavy engineering – Basic rack
ISO 678:1976 Straight bevel gears for general engineering and heavy engineering – Modules and
diametral pitches
ISO 701:1998 International gear notation – Symbols for geometric data
ISO 1122-1:1998 (E/F) Cor 1:1999 Cor 2:2009 Vocabulary of gear terms – Part 1: Definitions related to
geometry
ISO 1122-2:1999 Vocabulary of gear terms – Part 2: Definitions related to worm gear geometry
*ISO 1328-1:2013 Cylindrical gears – ISO system of accuracy – Part 1: Definitions and allowable values
of deviations relevant to corresponding flanks of gear teeth
*NOTE: Adopted as ANSI/AGMA ISO 1328-1-B14
ISO 1328-2:2020 Cylindrical gears – ISO system of accuracy – Part 2: Definitions and allowable values of
deviations relevant to radial composite deviations and runout information
*NOTE: Adopted as ANSI/AGMA ISO 1328-2-A21
ISO 2490:2007 Single-start solid (monoblock) gear hobs with tenon drive or axial keyway, 1 to 40 module
– Nominal dimensions
ISO 4468:2020 Gear hobs – Accuracy requirements
ISO 6336-1:2019 Calculation of load capacity of spur and helical gears – Part 1: Basic principles,
introduction and general influence factors
ISO 6336-2:2019 Calculation of load capacity of spur and helical gears – Part 2: Calculation of surface
durability (pitting)
ISO 6336-3:2019 Calculation of load capacity of spur and helical gears – Part 3: Calculation of tooth
bending strength
ISO/TS 6336-4:2019 Calculation of load capacity of spur and helical gears – Part 4: Calculation of tooth
flank fracture load capacity
ISO 6336-5:2016 Calculation of load capacity of spur and helical gears – Part 5: Strength and quality
of materials
*ISO 6336-6:2019 Calculation of load capacity of spur and helical gears – Part 6: Calculation of service
life under variable load
ISO/TS 6336-20:2022 Calculation of load capacity of spur and helical gears – Part 20: Calculation of
scuffing load capacity – Flash temperature method
scuffing load capacity – Integral temperature method
micropitting load capacity

ISO/TR 6336-30:2017 Calculation of load capacity of spur and helical gears – Part 30: Calculation
examples for the application of ISO 6336 parts 1,2,3,5
ISO/TR 6336-31:2018 Calculation of load capacity of spur and helical gears — Part 31: Calculation
examples of micropitting load capacity
ISO 8579-1:2002 Acceptance code for gears – Part 1: Determination of airborne sound power levels
emitted by gear units
ISO 9083:2001 Calculation of load capacity of spur and helical gears – Application to marine gears
ISO 9085:2002 Calculation of load capacity of spur and helical gears – Application for industrial gears
ISO/TR 10064-1:2019 Code of inspection practice – Part 1: Measurement of cylindrical gear tooth flanks
*NOTE: Adopted as AGMA ISO 10064-1-A21
ISO/TR 10064-2:1996 (E) Cor 1:2001 Cor 2:2006 Cylindrical gears – Code of inspection practice –
Part 2: Inspection related to radial composite deviations, runout, tooth thickness and backlash
ISO/TR 10064-3:1996 (E) Cor 1:2006 Cylindrical gears – Code of inspection practice – Part 3:
Recommendations relative to gear blanks, shaft centre distance and parallelism of axes
ISO/TR 10064-4:1998 (E) Cor 1:2006 Cylindrical gears – Code of inspection practice – Part 4:
Recommendations relative to surface texture and tooth contact pattern checking
*ISO/TR 10064-5:2005 Cor 1:2006 Code of inspection practice – Part 5: Recommendations relative to
evaluation of gear measuring instruments – Technical Corrigendum 1
*ISO/TR 10064-6:2009 Code of inspection practice – Part 6: Bevel gear measurement methods
ISO 10300-1:2014 Calculation of load capacity of bevel gears – Part 1: Introduction and general influence
factors
ISO 10300-2:2014 Calculation of load capacity of bevel gears – Part 2: Calculation of surface
durability (pitting)
ISO 10300-3:2014 Calculation of load capacity of bevel gears – Part 3: Calculation of tooth root strength
ISO/TS 10300-20:2021 Calculation of load capacity of bevel gears — Part 20: Calculation of scuffing load
capacity — Flash temperature method
ISO/TR 10300-30:2017 Calculation of load capacity of bevel gears – Part 30: ISO rating system for bevel
and hypoid gears — Sample calculations
ISO/TR 10300-32:2021 Calculation of load capacity of bevel gears — Part 32: ISO rating system for
bevel and hypoid gears — Sample calculation for scuffing load capacity
ISO 10825-1:2022 Gears – Wear and damage to gear teeth – Part 1: Nomenclature and characteristics
ISO 10825-2:2022 Gears – Wear and damage to gear teeth – Part 2: Supplementary information
ISO/TR 10828:2015 Worm gears – Worm profiles and gear mesh geometry
ISO 13691:2001 Petroleum and natural gas industries – High speed special-purpose gear units
*ISO 14104:2017 Gears – Surface temper etch inspection after grinding, chemical method
*NOTE: Adopted as ANSI/AGMA ISO 14104-A17
*ISO/TR 14179-1:2001 Gears – Thermal capacity – Part 1: Rating gear drives with thermal equilibrium at
95°C sump temperature
*NOTE: Adopted as AGMA ISO 14179-1
ISO/TR 14179-2:2001 Gears – Thermal capacity – Part 2: Thermal load-carrying capacity
ISO/TS 14521:2020 Gears – Calculation of load capacity of worm gears

ISO 14635-1:2000 Gears – FZG test procedures – Part 1: FZG method A/8, 3/90 for relative scuffing load
carrying capacity of oils
ISO 14635-2:2004 Gears – FZG test procedures – Part 2: FZG step load test A10/16, 6R/120 for relative
scuffing load-carrying capacity of high EP oils
ISO 14635-3:2005 Gears – FZG test procedures – Part 3: FZG test method A/2,8/50 for relative scuffing
load-carrying capacity and wear characteristics of semifluid gear greases
*ISO 17485:2006 Bevel gears – ISO system of accuracy
*ISO 18653:2003 Gears – Evaluation of instruments for the measurement of individual gears
*ISO/TR 18792:2008 Lubrication of industrial gear drives
*NOTE: Adopted as AGMA ISO 18792-A19
ISO 21771:2007 Gears – Cylindrical involute gears and gear pairs – concepts and geometry
*ISO/TR 22849:2011 Design recommendations for bevel gears
*NOTE: Adopted as AGMA ISO 22849-A12
*ISO 23509:2016 Bevel and hypoid gear geometry
*NOTE: Adopted as ANSI/AGMA ISO 23509-B17
IEC 61400-4:2012 Wind turbines – Part 4: Design requirements for wind turbine gearboxes

Fall Technical Meeting Papers: 2000–2021
2022 PAPERS
22FTM01. Development of a New Test Method to Investigate the Scuffing Load Carrying Capacity of Hypoid
Gear Oils
Author(s): Alexander Drechsel, Josef Pellkofer, Karsten Stahl
Highly loaded hypoid gears exhibit an unfavorable combination of high sliding velocities and high contact stresses
in tooth contact with regard to the failure mode scuffing. Beyond the loads and speeds that occur during gear
operation, the lubricant used and its additives have a significant influence on scuffing load capacity. Since it is
generally impossible to determine the influence of the lubricant on the load carrying capacity of gears on the basis
of physical or chemical oil data alone, experimental test methods are necessary. An experimental test method
was developed based on theoretical investigations. In order to achieve a reproducible test procedure, a running-in
procedure was specified based on the results of experimental investigations on a hypoid back-to-back test rig.
ISBN: 978-1-64353-121-2
22FTM02. Mechanical Power Loss of Spur Gears Subject to Various Surface Finish Pairings
Author(s): Isaac Hong, Emily Aneshansley, David Talbot
Heat generation due to friction at the gear contact interface is a parasitic energy loss and may require designers
to include active cooling systems further decreasing the net usable energy. It is known that changing the surface
roughness of the mating gear flanks influences friction in the contact. Presenting different surface finishes to the
contact directly influences the amount of asperity interaction. Gear designers and manufacturers must carefully
balance costs associated with surface finishing processes while achieving target goals for transmission design.
This study utilizes a closed form model to predict friction in mixed lubrication contact conditions as well as gear
mechanical power loss under a wide variety of surface finish pairings for several operating conditions consistent
with automotive applications.
ISBN: 978-1-64353-122-9
22FTM03. Aspects of Gear Noise, Quality, and Manufacturing Technologies for Electro Mobility
Author(s): Hartmuth Müller, Christof Gorgels
This paper explains the formation of transmission noise and the basic cause being the tooth mesh excitation of
gears. For detecting the excitation, metrological and functional methods are presented. The paper shows
mathematical principles describing the tooth mesh. Beside physical properties, psychoacoustic metrics rating the
hearing experience are introduced. Methods for influencing the tooth mesh and the derived rating are presented in
the field of macro geometric design and flank form modifications as well as flank surface modulation.
ISBN: 978-1-64353-123-6
22FTM04. Optimizing the Operational Behavior of Double Helical Gears by Means of an FE-Based Tooth
Contact Analysis
Author(s): Alexander Mann, Jens Brimmers, Christian Brecher
Double helical gears are becoming increasingly relevant, especially in the fields of drive technology. Interaction
effects between the two halves of the gear are becoming increasingly important to ensure low-noise operation. In
the current state of the art design processes the interactions between the individual gear meshes of the left and
right half are neglected.
This paper, therefore, presents a method for considering the quasi-static stiffness behavior of double helical gears
for gear design by using an FE-based approach. The developed method is validated by means of experimental
studies. The validated method allows to derive design and tolerance recommendations for double helical gears in
order to optimize the excitation behavior.
ISBN: 978-1-64353-124-3
22FTM05. In Process Measurement and Compensation for Manufacturing Skiving Cutters

Author(s): Stephen Williams, Xiaoyu Wang
Carbide skiving cutters present new challenges for manufacturing. We have developed two complementary
methods to address this. Firstly: we have developed a grinding path compensation, allowing flank errors to be
corrected, without altering the wheel profile. Secondly: we developed an in-process flank profile measurement
procedure, using an analogue probe, which calculates the reference geometry for the flank profile, and graphs the

measured deviations. For an involute reference curve, the measurement result will be directly comparable to a
traditional gear measuring machine report. However, for complex geometries we can assess whether the ground
flanks match the intended design directly, without referring to complex geometric design details. One can then see
what compensation should be applied for the desired outcome, without removing the cutter from the machine.
ISBN: 978-1-64353-125-0
22FTM06. Methods for Checking the Profile of the Path of Contact of Involute Gears
Author(s): Zhaoyao Shi, Yanqiang Sun, Haobin Li
The profile of path of contact (PPC) is another significant characteristic curve beside involute and helix. During the
gear generating machining, this line is consistent with machining curve. During the gear transmission, this line is
also consistent with working curve. Therefore, the quality of gear machining and transmission can be reflected by
the PPC. However, the existing gear measuring instruments cannot measure it. The theoretical model is given
combining the forming principle of PPC. Based on the existing GMC, two methods for measuring the deviation of
PPC are proposed, including the four-axis method and the three-axis method. In measurement methods, the
measurement of PPC and involute profile is unified. The measurement practice shows that the measurement and
evaluation of PPC can be conveniently realized.
ISBN: 978-1-64353-126-7
22FTM07. Finding the Right Task for Optical Gear Metrology

Author(s): Markus Finkeldey, Christof Gorgels
Optical metrology is an established technology in the coordinate measurement community, with a growing impact
on the specialized field of gear metrology. The idea of a contactless and thus fast technology for quality control is
promising. Nevertheless, every new technology raises questions: How to use this technology and what are
meaningful use cases? Looking deeply into the field of optics evokes even more questions: What kind of optical
technologies do exist, what is the adequate technology for your application and do I need a special sample
preparation? This paper provides a quick overview about optical metrology for gear analysis and provides some
field results of optical gear measurements. The results are focused on gears for automotive applications,
especially for the expanding area of electric drivelines.
ISBN: 978-1-64353-127-4
22FTM09. A New Low Pressure Carburizing Solution in a Pit vs. Traditional Pit Carburizing Methods
Author(s): Thomas Hart
Pit LPC is a new and revolutionary furnace system that is a drop in replacement for traditional atmosphere pit
carburizing solutions. This approach can handle the same large and/or long loads with deep ECD while reducing
the process time and utility costs. These benefits drastically increase a ROI when converting from atmosphere
carburizing to LPC while eliminating carbon emissions associated with gas carburizing.
ISBN: 978-1-64353-129-8
22FTM10. Mathematical Model of a Straight Bevel Gear on the Straight Bevel Coniflex Generator and Gear
Flank Correction
Author(s): Yi-Pei Shih, Yu-Cheng Hung, Bor-Tyng Sheen, Szu-Hung Chen, Kuan-Heng Lin
Coniflex cutting, a popular mass production method for straight bevel gears, employs two giant interlocked circular
cutters to generate tooth surfaces. By controlling the tool pressure angle, Coniflex cutting enables profile and
lengthwise crownings that result in advantageously low assembly sensibility. This paper proposes a mathematical
model of a Coniflex bevel gear produced on a dedicated machine, whose coordinate systems between cutters and
work gear are empirically well-defined. Once the tooth surface is derived from coordinate transformation and gear
enveloping theory, ease off and tooth contact analysis can be conducted numerically; after which flank correction
is achieved using sensitivity analysis and optimization methods. Both the proposed model and the flank correction
are validated using cutting experiments on a straight bevel Coniflex generator No. 104.
ISBN: 978-1-64353-130-4
22FTM11. Closed Loop for Gears: Some Case Studies

Author(s): Massimiliano Turci, Vincenzo Solimine
The steps to realize good gears are design, manufacturing, measurement, and test. Each step has effect on the
next one, and the last one turns back on the first one, and so on. This workflow is valid in several application, from
gearboxes with zero-backlash, to automotive transmissions and industrial gearboxes for lifting in offshore
application. This workflow is called “closed loop”

The paper will present some cases for bevel, cylindrical and worm gears:
- exchange of information between design dept. and quality control to compare designed, estimated
and realized microgeometry and LTCA
- generation of K-Charts for the drawings that can be modified by the designer in case of exceptions
for not respected but acceptable requirements,
- estimation of the twist due to manufacturing process.
ISBN: 978-1-64353-131-1
22FTM12. Modern Green and Hard Machining of Double Helical Gears

Author(s): Andreas Mehr, Oliver Winkel, Scott L. Yoders
Green machining of double helical gears can be realized by multi-axis milling, form milling, hobbing and gear
shaping. The advantages and the limits of each single gear cutting method is presented in this article. Especially
the multi-axis milling and the gear shaping allow the manufacturing of herringbone gears (no gap between the two
helical gears), too. For the hard machining, the focus is on the multi-axis milling and generating grinding with small
diameter grinding worms. The latest developments on the grinding abrasives and the machine tool enable the
continuous generating grinding to become a real alternative to the established profile grinding of double helical
gears.
ISBN: 978-1-64353-132-8
22FTM13. Effect of Tooth Root Fillet Design on Tooth Root Stress in Short Fiber Reinforced Plastic Gears
Author(s): Wassiem Kassem, Manuel Oehler, Oliver Koch
The geometry of plastic gears is usually based on conventional steel gears, which are bound to the restrictions of
the machining production of gears. The injection molding process provides more design freedom here. In this
work, simulative results in terms of tooth root stress in plastic gears with various tooth root fillet designs are
shown. The simulation method is based on finite element analysis and takes into account the different fiber
orientation as well as the complex material behavior of short fiber reinforced plastics.
The analysis includes fully rounded, elliptical and bionic tooth root fillets. In addition to the tooth root stress in the
initial state, results are also presented for the geometry changed by wear during operation.
ISBN: 978-1-64353-133-5
22FTM14. Investigations on the Tooth Root Bending Strength of Larger-Sized Induction Hardened Gears
Author(s): Holger Cermak, Thomas Tobie, Karsten Stahl
Especially for larger-sized gears surface hardening is an economical and technological alternative to case
hardening. Due to the necessary high case hardening depths required for larger case hardened gears and due to
technological boundaries (e.g., heat treatment furnace size and heat treatment duration) typical surface hardening
processes such as flame or induction hardening can exhibit their benefits for these parts. In the framework of this
paper, the influence of induction hardening on the tooth root bending strength of larger-sized gears is investigated.
Therefore, different variants of larger gears which were induction hardened gap-by-gap are compared. In order to
gain a deep understanding, a systematical variation of the surface hardening depth, gear size (mn = 14 mm and
20 mm), and surface condition was carried out.
ISBN: 978-1-64353-134-2
22FTM15. On the Potential of High-Ratio Planetary Gearboxes for Next-Generation Robotics

Author(s): Pablo Lopez Garcia, Anand Varadharajan, Stein Crispel, Dirk Lefeber, Tom Verstraten, Marcin Wikło,
Georgios Vasileiou
On the eve of modern robotic devices leaving their protective safety fences to enter our homes and interact with
us, the gearboxes used in the actuators that power these devices still face significant challenges. Modern
collaborative robots, including cobots, exoskeletons, prostheses, or AGVs, place more demanding weight,
efficiency, and affordability requirements on their gearboxes, which Cycloidal and Harmonic Drive technologies
have difficulties fulfilling.
This situation provides a highly dynamic field for engineering research. In this paper, we assess the potential of
high-ratio planetary gearboxes for modern robotic applications, using an assessment framework to identify their
main advantages and limitations, which we then analyze in further detail. The resulting insights indicate that
compact planetary gearboxes may see a significant come-back in the next generation of robots.
ISBN: 978-1-64353-135-9

22FTM16. A Model for Considering Wheel Body Deformation in Tooth Contact Load Distribution
Author(s): Benjamin Abert, Georg Hammerl
Gearbox wheel bodies are often designed and manufactured to maximize power density. Strategic use of
recesses and bores can achieve significant weight savings in gears. However, wheel bodies are known to have an
influence on the gear system.
Many CAE tools use the Weber-Banaschek approach to determine the gear stiffness. This is a proven method
that has been deemed sufficiently for the simulation of tooth contact. However, this approach uses a simplified
consideration of the wheel body as an elastic half-space and cannot represent complex wheel bodies.
This paper describes a calculation method which efficiently determines the stiffness of any wheel body geometry
using statically reduced stiffness matrices from an FE model and links them to an analytical model of the tooth
contact.
ISBN: 978-1-64353-136-6
22FTM17. A Decomposition of the Torsional Stiffness of a Worm Gearbox into Individual Components
Author(s): Kevin Daubach, Manuel Oehler, Oliver Koch
In worm drive applications with precise transmission, the torsional stiffness of the worm gearbox is an important
parameter for the positioning accuracy. The torsional stiffness is a result of elasticities from all gearbox
components along the load path, which leads to various options for an optimization of the torsional stiffness within
the design process of worm gearboxes. However, a targeted optimization with high effectiveness requires
information about the distribution of displacements across the gearbox components.
A modeling approach is presented to decompose the total angular displacement of worm gearbox shafts under
load into individual components, by which sources with high displacement proportions can be identified as targets
for the optimization. The distribution of displacement proportions is investigated for specific worm gearboxes.
ISBN: 978-1-64353-137-3
22FTM18. Unconventional Gear Profiles in Planetary Gearboxes

Author(s): Anand Varadharajan, Pablo Lopez Garcia, Dirk Lefeber, Stein Crispel, Tom Verstraten, Bram
Vanderborght
The efficiency of high ratio planetary gear trains (PGTs) is mainly constrained by the meshing efficiency of acting
gears in each stage. Such gear wheels, predominantly with involute teeth profiles, work with a meshing efficiency
of around 99%. Yet, the overall efficiency of the gearbox drops to even below 70% when gear ratios of a few
hundred are exceeded. Unconventional gear profiles are capable of solving the efficiency issue in high ratio
planetary gearboxes. A review of existing PGTs with unconventional profiles is discussed along with other
possible gear profiles to increase efficiency. The existing unconventional gear profiles are found to have high
transmission errors and are intolerant to manufacturing inaccuracies thereby requiring further research to improve
them.
ISBN: 978-1-64353-138-0
22FTM19. Implementation of a Gear Health Monitoring System on a Power Recirculating Test Rig Using the
Average Log Ratio (ALR) Algorithm
Author(s): Matthew Wagner, William D. Mark, Aaron Isaacson
The ability to detect the onset of a gear system failure via accelerometer measurements is of interest in a
research environment as well as in gear systems deployed in the field. An accelerometer based gear health
monitoring system is described which was developed for use in a laboratory setting for monitoring power
recirculating gear tests. Even angle resampling, time synchronous averaging (TSA), and average log ratio (ALR)
algorithms are utilized to detect the onset of gear damage. A summary of these signal processing concepts is
given, along with an overview of system hardware, signal processing workflow, and sample data.
ISBN: 978-1-64353-139-7
22FTM20. Enhanced Calculation Method for Tooth Flank Fracture Risk with Consideration of Tensile
Residual Stresses in Larger Material Depths
Author(s): Daniel Müller, Thomas Tobie, Karsten Stahl
Tooth flank fracture (TFF) is a gear fatigue failure mode, which is initiated in larger material depths beneath the
active flank. Therefore, the residual stresses in larger material depths are decisive for TFF. In these larger
material depths, the residual stress conditions are almost unknown up to now. This paper presents a calculation
method to assess the residual stresses in gears. The calculated residual stress profiles also consider the existent

tensile residual stresses in larger material depths. Based on these predicted residual stress profiles, calculation
methods for TFF, including the standard calculation of ISO/TS 6336-4, were extended to consider not only
compressive but also tensile residual stresses, which was not possible so far.
ISBN: 978-1-64353-140-3
22FTM21. Experimental Evaluation of Wind Turbine Gearbox Structural Models Using Fiber Optic Strain
Sensors
Author(s): Unai Gutierrez Santiago, Xabier López Fuentes, Alfredo Fernández Sisón, Henk Polinder, Jan-Willem van
Wingerden
The rated power and size of wind turbines have grown considerably to reduce the cost of energy from wind. This
has pushed gearbox manufacturers to introduce multiple technological innovations to boost the torque density of
current designs. One of the critical challenges of next-generation gearbox designs is to optimize structural
components and gears. Complex models are needed to predict the gearbox components' load-carrying capacity
and fatigue life. These tools need to be verified through experimental evaluation. This study evaluates the
structural calculation models used for a modern 6MW wind turbine gearbox through physical testing. The
measurement system is composed of fifty-four fiber Bragg gratings. A good correlation between the structural
models and the test results in a full-scale back-to-back test bench has been achieved.
ISBN: 978-1-64353-141-0
22FTM22. Test Rig for Crowned Spline-Joints with Optimized Surface Treatments Under Misaligned
Conditions
Author(s): Gerrit Hellenbrand, Dieter Mevissen, Jens Brimmers, Christian Brecher
Increasing the load capacity of spline-joints in shaft-gear connections, such as UHBR-aero-engines, leads to a
lean and efficient design of the power train components. An approach for this is to apply optimized surface
treatments, such as coatings and laser structuring, which can reduce the risk of upcoming wear and fatigue
phenomena. To assess the potential of these surface treatments for spline-joints, tests under real working
conditions need to be carried out. As the application is an UHBR-aero-engine gas turbine, component tests are
not applicable in the application for economic reasons. Hence, a design for a test spline connection, as well as a
test rig for investigations of the wear and fatigue behaviour of surface treated spline-joints are presented.
ISBN: 978-1-64353-142-7
22FTM23. Results of ISO/TS 6336-22 Evaluating Full Contact Zone

Author(s): Robin Olson, David Talbot, Mark Michaud, Jonathan Keller, John Amendola, Sr.
ISO/TS 6336-22 (Calculation of micropitting load capacity) is the ISO technical specification containing a proposal
for calculations of the risk of micropitting in gear sets. It assesses micropitting risk through a safety factor
calculated as the minimum specific film thickness divided by a permissible specific film thickness. In a previous
paper, the calculations were performed using the simplified method (Method B) that evaluates points on the path
of contact. This was done for three gear sets that experienced micropitting in operation. A more accurate
calculation for these cases (Method A) calculates the specific film thickness across the entire contact zone. This
paper applies this Method to the case study from the previous paper. The results are compared to micropitting
observed in operation.
ISBN: 978-1-64353-143-4
22SP1. Noise Analysis for e-Drive Gears and In-Process Gear Inspection
Author(s): Antoine Türich, Klaus Deininger
A new inspection concept developed by Gleason features a combination of double flank roll testing and laser
scanning. With this new approach gear inspection now can be performed as fast as a typical hard finishing
operation takes. As a result, 100% in-process inspection has become a reality, eliminating the need for statistical
process evaluation. In addition, the measured data can be further evaluated concerning waviness in profile and/or
lead allowing the evaluation of the noise behaviour. Hence, this new system allows an up to 100% in-process
noise analysis prediction of the finished gear. This new inspection concept has been integrated with a modern
grinding machine and a fast and flexible automation system to create the Hard Finishing Cell including a Closed
Loop correction system.
ISBN: 978-1-64353-144-1

2021 PAPERS
21FTM01. Investigation of the Effect of Application of Non-Conventional Root Profiles for Reduction of
Bending Stresses in Helical Gear Drives
Author(s): Ignacio Gonzalez-Perez, Alfonso Fuentes-Aznar, Jose Calvo-Irisarri, Alfredo Fernandez-Sison, Harri
Aurrekoetxea-Arratibe
The substitution of the conventional trochoid root profile in spur and helical gears by non-conventional root
profiles, based on elliptical or Bèzier curves, to reduce the maximum bending stress at the gear root surfaces has
been the subject of an intensive research recently. The application of finite element models in which the load is
applied at the highest point of single tooth contact has been mainly used for those studies. However, a complete
review of the stress field at the fillet surface and its variation along a cycle of meshing is still missing. The adjacent
pair of teeth when it carries part of the load causes compressive stresses on the root area that deserves to be
considered for a comprehensive study of the possible benefits of application of non-conventional root profiles.
This paper focuses on the investigation of the variation of the normal stress in the perpendicular direction to the
root line between adjacent teeth. Such variation will be obtained for two cycles of meshing by considering finite
element models with five pairs of teeth, so that the effect of load sharing between adjacent pairs of teeth will be
considered. This study will provide the variation of the alternating range normal stresses on the root surface in
longitudinal direction of the gear teeth for tooth root profiles based on Hermite, elliptical, and Bèzier curves and
their comparison in terms of the mentioned stresses with those obtained for conventional root profiles. Several
numerical examples corresponding to an existing design of a helical gear drive show that the reduction of the
maximum principal stress is possible using non-conventional root profiles, although an increment of the alternating
component of the normal stress occurs, which may lead to the reduction of the expected fatigue life of the gear
drive.
ISBN: 978-1-64353-095-6
21FTM02. Transient Friction and Wear Simulation of Worm Gears During Running-In
Author(s): K. Daubach, M. Oehler, B. Sauer
The load capacity of worm gears strongly depends on the size of the contact pattern. Worm wheels are often
manufactured by using an oversized hob, which results in a relatively small initial contact pattern. Wear on the
worm wheel with a softer material during the running-in process increases the contact pattern and thereby the
load capacity. For the investigation of the continuous change of friction in the tooth contact during that process, a
tribological simulation program is used. With a simplified model of the EHL-tooth contact, boundary as well as fluid
friction are calculated locally, and the tooth efficiency is evaluated. The included wear model associates abrasive
wear with solid friction energy occurring in the tooth contact and allows a time-dependent simulation by
considering the wear-modified tooth flank in the tribological calculation.
The simulative results are compared with experimental wear studies on the running-in of worm gears. Since
various values are determined in the simulation model, the comparison covers different aspects to verify the
model. However, for measurement reasons a comparison is taking place on the macro scale. The tooth friction is
reflected by the measured efficiency of the gearbox on the test bench. Wear is on one hand a directly measured
value, on the other hand it changes the geometry of the tooth flank and influences thereby the unloaded
kinematics of the gears. Both aspects are considered for a verification of the wear calculation.
ISBN: 978-1-64353-096-3
21FTM03. Tooth Flank Fracture – Design Process for a New Test Gearing and First Test Results
Author(s): Daniel Müller, Thomas Tobie, and Karsten Stahl
Tooth flank fracture (TFF) is a gear fatigue failure mode. TFF differs from tooth root breakage and pitting in that
the crack emerges below the hardened case of the active flank. However, like tooth root breakage, it leads to a
total breakdown of the gears in contact and often in severe failure of the entire transmission. TFF recently has
occurred more frequently, especially in larger sized gears. This makes it all the more important to investigate TFF
failures. In order to avoid TFF in the future, a calculation method, that must be applicable in the design phase is
needed and should be widely verified by experimental results. For the systematic investigation of TFF, smaller
sized test gears are used. So far, only test gears for TFF with a center distance of 200 mm are commonly used.
Although the gears are significantly smaller than those used in the relevant industrial applications, extensive
experimental investigations still result in high costs. A smaller sized test gearing with a center distance of 91.5 mm
would reduce the costs of manufacturing the test gears significantly and also offer more testing capabilities based
on the use of standardized FZG back-to-back gear test rigs. Based on the experimental results of the test gears
with a center distance of 200 mm, a calculation approach (ISO/TS 6336-4) was developed in the FVA 556 I
research project. In this work, this practical approach is used to design a smaller sized test gearing with a center
distance of 91.5 mm. The test gear pairing is tested with a back-to-back test rig and initial test results are shown

and discussed. In addition, results of further investigations regarding microstructure, hardness and residual
stresses are presented.
ISBN: 978-1-64353-097-0
21FTM04. Effect of the ISO 6336 3:2019 Standard Update on the Specified Load Carrying Capacity Against
Tooth Root Breakage of Involute Gears
Author(s): Stefan Sendlbeck, Maximilian Fromberger, Michael Otto, and Karsten Stahl
Part 3 of the ISO 6336 standard contains a verified specification for calculating the tooth bending strength of
involute gears. In November 2019, an update of the previous version from the year 2006 was issued, which
includes more detailed calculation methods based on the most recent research findings. For an optimal gear
design, gear engineers need to be aware of how the changes in the standard affect the overall calculation result,
since the revised standard can yield a higher or lower safety factor against tooth root breakage.
This paper provides a detailed summary of the key changes in ISO 6336-3:2019, outlines their overall effects on
the basis of a calculation study, and presents a comparison of the results to the previous version of the standard,
ISO 6336-3:2006. The key changes in ISO 6336-3:2019 are a new load distribution influence factor that accounts
for the effects of high overlap ratios and a more precise consideration of the helix angle on the stresses.
Furthermore, the standard now also covers the determination of the tooth root geometry of internal gears by
means of a shaper cutter. To investigate these changes and their overall effect, we vary the contact ratio by using
gears with different transverse contact ratios and overlap ratios as a basis for computing the specifications of the
standard. In addition, by simultaneously varying the transmission ratio and the tool tip radius, we investigate the
effect on the calculation of internal gears with different tooth root geometries. The findings of this research give a
detailed insight into how the update enhances the ISO 6336 standard and how they affect the load carrying
capacity calculation.
ISBN: 978-1-64353-098-7
21FTM05. Double Differential for Electric Vehicle and Hybrid Transmissions – Sophisticated Simplicity
Author(s): Hermann Stadtfeld, Haris Ligata
The fascination of the automotive differential has led to the idea to build a second differential unit around a first
center unit. Both units have the same axes around which they rotate with different speeds.
The potential of double differentials as ultrahigh reduction speed reducers is significant. Only the tooth-count of
the gears in the outer differential unit must be changed to achieve ratios between 5 and 80 without a noticeable
change of the transmission size.
Double differentials are well suited for high input speeds. The fact that the carrier rotates with about half of the
input speed reduces the relative motion and with it the sliding velocity to 50% of the value of two conventionally
meshing bevel gears which roll with the same input speed.
Ground spiral bevel gears are recommended for the double differential application. Due to the load sharing of the
two opposite planets, the torque of each gear is only 50% compared to a conventional bevel gear mesh. This
effect results in very high-power density of this already very compact unit.
Also, the efficiency of the double differential is high in contrast to the fact that always two pairs of gears are
transmitting the rotation and torque. Double differentials show good efficiency results, which qualifies this new
transmission type very well for the speed reduction and transmission in electric vehicles and hybrids.
In addition to electric vehicles and hybrid cars, there are many other applications in the industry which require high
ratios. Double differentials could be used in helicopters, wind turbines, agricultural equipment, and many other
industrial applications.
The objective of the paper is to compare a transmission concept, which is based on bevel gear technology, with
cylindrical gear-based solutions, for designers and manufacturers of high reduction transmissions to have an
additional technology available for their different applications.
ISBN: 978-1-64353-099-4
21FTM06. Bevel Gear Strength Rating – The Appropriate Combination of FE with Rating Standards
Author(s): Jürg Langhart, Markus Bolze
Strength rating of bevel gears according to standards such as AGMA, ISO, etc. is executed based on virtual
cylindrical gears, only modified by a few specific bevel gear factors. The rating method of these standards also
includes the calculation of permissible stresses and finally resulting safety factors. Furthermore, the integrated S-
N curves consider also an increased permissible stress during limited life and allow a lifetime prediction.

The contact analysis for bevel gears allows a rating of the stresses. It allows the individual to consider flank
modifications such as crowning, twist, etc., including the corresponding displacements. A lack of the contact
analysis is the calculation of permissible stresses and hence no rating of safety and lifetime is available.
To combine both methods, the standard requires a certain level of adaptation possibilities, to tune the major
effects which influence the stresses. Whereas ISO 10300 (edition 2014) has factors that allow an adaptation, the
AGMA 2003:C10 standard has little possibilities. Also, the bending stress numbers of AGMA 2003 are much lower
and differ remarkably from the contact analysis values.
The process to combine both calculation approaches increases the accuracy in the rating of bevel gears
significantly. The first step is to determine the E, P, G and Alpha displacements for a sample bevel gear pair. By
using the E, P, G and Alpha displacements, the largest possible contact pattern is developed, strictly avoiding any
edge contact. Based on the stress numbers by the contact analysis, the relevant parameters of the rating
standard are derived.
As a next step, using the fast standard calculation, the bevel gear macro geometry is optimized by variation of the
key parameters. All these solutions can be evaluated with various failures modes such as root bending, pitting,
scuffing, and flank fracture.
ISBN: 978-1-64353-100-7
21FTM07. Use of Duty Cycles or Measured Torque-Time Data with AGMA Ratings
Author(s): Ulrich Kissling
Nowadays continuous torque measurement on gearboxes is increasingly popular, not only on very sensitive
installations but also on many industrial gearboxes and wind turbines. When the transmitted load is not uniform,
consideration should be given not only to the peak load and its anticipated number of cycles, but also to
intermediate loads and their numbers of cycles. This type of load is considered a duty cycle and may be
represented by a load spectrum. In such cases, the cumulative fatigue effect of the duty cycle is considered in
rating the gear set. A method of calculating the effect of the loads under these conditions, such as Miner’s Rule, is
not explained in AGMA rating methods (as AGMA 2001, 2101, 2003) but a reference is given to ISO/TR 10495
(nowadays replaced by ISO 6336-6:2019).
In this paper the application of torque spectra in AGMA rating methods is described. Furthermore, a procedure to
convert measured (or calculated by numerical simulation) torque data into a torque spectrum according to the
definition in ISO 6336-6 is described. This task is simple if the torque is always positive, but quite complicated
when also negative torque sequences happen.
The torque spectrum must represent the load on each single tooth, therefore in a first step the continuous torque
course has to be segmented in individual torque peaks applied on one tooth. If only positive torque occurs (no
load reversal), the "Simple Count" method can be used. The method counts how often a torque value happens to
be in a certain torque range. A tooth is always loaded by a torque value starting at zero to a peak, hence it is
subjected to pulsating stress (stress ratio R=0). Tooth bending stress calculation according to AGMA is assuming
pulsating stress, so the result of the “Simple Count” method can directly be used for the tooth bending strength
verification.
For complex loads, where the torque has both positive and negative signs, the “Rainflow method” (ISO 12110-2
[8]) should be applied. 'Rainflow Counting' is a method to determine the number of fatigue cycles present in a
load-time history. The method is used in the analysis of fatigue data in order to reduce a spectrum of varying
stress into an equivalent set of simple stress reversals. So, a tooth is loaded by cycles with a high and a low
torque (respectively stress), having a variable stress ratio R ≠ 0. To comply with the rules of AGMA ratings, a
reverse loading factor must be used to modify the admitted sat values for tooth bending. In ISO, this factor is the
mean stress influence factor YM which must be defined for every bin of the torque spectrum.
In the final part of this paper a practical application of the above method is presented.
ISBN: 978-1-64353-101-4
21FTM08. Defining The Tooth Flank Temperature in High Speed Gears

Author(s): John Amendola and John Amendola III, Robert Errichello
In defining total contact temperature the tooth flank temperature is as significant in the calculation as the flash
temperature. Work done in preparation to writing 19FTM24 revealed that the applied ksump multiplier value for
applications with spray lubrication should be greater than > 1.2 for high speed gears when calculating a tooth
flank temperature. This procedure is described in AGMA 925-A03, Section 6.3.1 equation (91). In order to have a
comparable risk assessment with MAAG “63”, MAAG “83” and ANSI/AGMA 6011-J14, Annex B, it was
determined a value of ksump = 1.42 is necessary otherwise AGMA 925 is not reliable for assessing scuffing risk for
high speed gears. However, further investigation suggests variable values of ksump are required to accurately

calculate the tooth flank temperature relative to pitch line velocity. Referenced documents, with supporting
comprehensive test data and testing results of high speed gears both indicate a higher range of tooth body
temperatures increasing with pitch line velocity. This is corroborated by field experience conducted by Artec
Machine Systems. This paper improves the methodology for determining the tooth flank temperature. Two
methods are proposed for assessing scuffing risk when applying AGMA 925 for high speed gears. Both methods
provide similar results.
ISBN: 978-1-64353-102-1
21FTM09. Algorithm-Based Optimization of Gear Mesh Efficiency in Stepped Planetary Gear Stages for
Electric Vehicles
Author(s): Christian Westphal, Jens Brimmers, Christian Brecher
The electrification of the automotive powertrain confronts the gearbox development with new challenges. High-
speed concepts require higher gear ratios, which cannot be optimally achieved with simple cylindrical gear stages.
For this reason, stepped planetary gear stages are increasingly used, as they offer high power density at high
gear ratios. To increase range and energy efficiency, the gear mesh losses are of great importance and must be
considered in the gear design.
The design of the macro geometry of gears is usually focused on ensuring the load-carrying capacity. In the
design of stepped planetary gear stages, there are constraints due to assembly restrictions as well as additional
degrees of freedom, such as the division of the total gear ratio. Due to many adjustable geometry parameters and
design combinations, manual optimization of the gear geometry would not be effective.
In this paper, a method for an automated optimization of the macro geometry of stepped planetary gear stages to
improve the gear mesh efficiency is presented, which considers the assembly restrictions. An FE based tooth
contact analysis is used to evaluate the design objectives: NVH (Noise, Vibration, Harshness), load-carrying
capacity, and efficiency. Since these objectives require different design strategies, a weighting of the objectives is
necessary. A particle-swarm algorithm is used to optimize the gear geometry and the tool data. Tooth flank
pressure, peak-to-peak transmission error, tooth root stress, and efficiency are evaluated. The influence of the
weighting of the design objectives on the gear design is shown. The results of various optimizations are
compared, and an efficiency-optimized variant is selected for a specific application.
With the method presented in this paper, it is possible to design the macro geometry of stepped planetary gear
stages using FE-based tooth contact analysis and to optimize the operational behavior for a given application.
ISBN: 978-1-64353-103-8
21FTM10. Particle-Based Phyllosilicate-Additive for Efficiency Improvement and Surface Protection

Author(s): Petr Chizhik, Stefan Bill, and Scott Gardiner
Croda Int Plc is a developer and manufacturer of an innovative phyllosilicate-based surface treatment additive
technology for gears and bearings. The particles with a platelet shape use lubricants as a carrier and build
through their adsorption a protective phyllosilicate-based coating on the surface. The modified surface has a
significantly lower surface roughness, which ensures a better load distribution and lower local pressure.
Additionally, due to the special layered material structure, the particles can be sheared in the tribological contact,
which leads to a significant reduction in friction. All in all, when applying the products, treated systems can run
better with reduced friction, wear, surface roughness and temperature. These effects lead to higher efficiency and
longer lifetime.
ISBN: 978-1-64353-104-5
21FTM11. Design and Simulation of a Back-to-Back Test Rig for Ultra High Cycle Fatigue Testing of Gears
Under Fully Reversed Load
Author(s): J. Lövenich, M. Trippe, O. Malinowski, J. Brimmers, S. Neus, C. Brecher
Gear units for turbomachinery, especially in the aerospace sector, place high demands. In addition to the high
power density, the demands are also increased regarding the operating temperatures compared to automotive
applications. Furthermore, the high operating speed excites vibrations in the higher frequency range, which also
poses challenges for the transmission design in terms of NVH. The high dynamics of over 12 000 rpm combined
with the high number of load cycles under fully reversed load (N > 108) that an aviation planetary gearbox
experiences makes load capacity tests with standardized back-to-back test rigs uneconomical or even impossible
due to the extremely long testing times. To enable the Ultra High Cycle Fatigue (UHCF) testing, a high-speed
back-to-back test rig was developed. In addition to the design, particular focus is placed on the thermal and
dynamic simulation of the test rig. These two aspects are the basis for a safe commissioning and a successful
testing. In the area of thermal simulation, the behavior of the test rig components in the operating temperature
range from room temperature to T > 100°C is investigated regarding the thermal expansion and the resulting

tolerances. The dynamic simulation deals with the vibration behavior of the test rig. Special focus is placed on the
tooth mesh frequency and the natural frequencies of the components. As a result, the operating points for testing
are defined and the operational safety is ensured. In addition, for providing a basis for the investigation of aircraft
transmissions, the paper shows fundamental ideas for the design of high-speed back-to-back gear test rigs.
ISBN: 978-1-64353-105-2
21FTM12. NVH Analysis of an Axle Drive with Bevel Gearset

Author(s): Davide Marano, Timo Giese, Saeed Ebrahimi
The geometry of bevel gears, together with the applied ease-off and the misalignment are introduced, and the
excitation orders related to the gears and bearings are calculated. The EAxle is modeled as a flexible multi-body
system, and the theoretical aspects related to the penalty contact formulation and modal reduction (Craig-
Bampton method) are discussed. The NVH performance of the EAxle is evaluated as a function of the mounting
distance (H), showing a significant reduction of the accelerations on a control point for a specific positive mounting
distance. Finally, housing sound pressure level (SPL) is compared for the selected scenarios, showing a
significative improvement for the optimized mounting distance configuration.
ISBN: 978-1-64353-106-9
21FTM13. Integrated Optimization of Gear Design and Manufacturing

Author(s): Massimiliano Turci
The word “optimization” is becoming fashionable, also with regard to gear design. It is applied to both macro-
geometry and micro-geometry. The approach can be of various types: analytical pre-optimization with different
objectives, bulk generation of variants, multi-objective and multi-disciplinary commercial optimizers, generative
optimization, and even artificial intelligence. Sometimes the best solution is presented directly, other times the
choice is left to the user according to multiple criteria. However, these are all scenarios that assume that the
manufacturer will accept any geometry indicated by the designer. This is not certainly the case with the industrial
gearboxes on catalog, for which standard cutting tools are used to reduce cost and keep available the interchange
of suppliers; nor with special gearboxes, “goods to order,” in which the producers try to use cutting tools already in
the tool room. Even in the automotive industry, however, manufacturers try to use existing cutting tools as much
as possible, at least during prototyping and for small batches.
After presenting some design optimization techniques adopted in different companies, the focus of the paper
shifts to some business scenarios where manufacturing has been equipped with a software for a semi-automatic
selection of hobbing and pinion type tools, starting from the macro-geometry of the gear. In particular, it will look at
the case where a paper database of more than ten thousand hobs, with different dimensioning modes, has
requested to be harmonized into a single computer database. The software allows the search for hob even with
“modified rolling,” a method very widespread in the automotive industry, practically “unknown” for industrial
gearboxes.
Finally, for companies that have both design and manufacturing departments, a design optimization with a list of
cutting tools as main boundary will be presented.
ISBN: 978-1-64353-107-6
21FTM14. Investigation of Gear Surface Topography and Deviations in Gear Power Skiving Through
Advanced CAD Modeling Based Simulation
Author(s): Nikolaos Tapoglou
Power skiving is an emerging gear cutting process that has been identified as a process that can provide a step
change in the production rate of high precision internal and external involute gear forms. The continuous
generating principle is the basis of the cutting process that ensures the increased throughput of the process that is
significant for internal gears. The understanding of the loads applied in the cutting tool and the gear as well as the
final characteristics of the gear machined through power skiving is of key importance in the optimization of the
cutting process. The present research focuses on two strands, first the development of a novel CAD based
simulation platform that is able to simulate the power skiving process and calculate the cutting forces and the
resulting gear topography. The second strand includes the validation of the model with analytical and
experimental data from literature. In depth, investigation in the quality of gears produced is presented as part of
this study with a focus in the influence of key process parameters in the resulting gear quality. Through this study
a series of process maps can be drawn that assist in the selection of the most productive parameters for
machining involute gears.
ISBN: 978-1-64353-108-3
21FTM15. Power Skiving – A Step Changing Manufacturing Process Applicable to Multifunctional 5-Axis
Machine Tools
Author(s): Bethany Cousins, Chao Sun, David Curtis, Michael Farmery, Steven Staley, Ben Cook

developing gear machining methods using multifunctional 5-axis machine tools with the expertise from
collaboration with multiple partner companies. One machining method applicable to multifunctional machine tools
is power skiving. This modern gear cutting process is gradually being adopted by industry, but its application is
considered a secretive black art. The focus is to develop and quantify the capabilities and publicize this for the
benefit of industry. The initial test geometry was a spur gear of 4.75-inch diameter and DP 6.5, which had teeth
roughed and finished in 6 minutes 20 seconds, achieving a quality of AGMA 2015-A01 class A5 (AGMA 2000-A88
class Q12).
Further test geometries have been trialed, including helical gears, ring gears, and internal splines, to ascertain
how process performance transfers to alternate geometries and what the key process variables affecting
productivity and gear quality are. Software models have been developed to predict cutting forces and establish
cutting parameters for new geometries in order to expedite the process development. A range of cutting
parameter strategies has been employed to establish an optimal approach for enhanced quality and reduced
vibration. Cutting tool life has also been established for a range of geometries and parameter sets with a view to
quantifying the commercial viability of the process.
Power skiving offers great opportunities for production with step-changing productivity, particularly for internal
gears, whilst offering high quality finishing capabilities and being applicable on a 5-axis machine tool with its
inherent flexibility and multi-functionality.
ISBN: 978-1-64353-109-0
21FTM16. An Accurate Method of Generating Tool Paths for Helical Gears with Crowning Modifications Using
a 5-axis CNC Machine
Author(s): Fei Shen, Luis Vega, Mohammadrafi Marandi, Christoph Kossack, Joshua Tarbutton, Gert Goch
To manufacture gears, special machine tools and corresponding processes, such as hobbing, shaping, planing,
profile milling, and broaching, are usually needed. However, the huge investment in such gear machining is
prohibitive for manufacturers, which only produce the gears in small batches on an annual basis. To overcome
this economic problem in the manufacturing of gears, standard 5-axis CNC machines were proposed as an
alternative tool for machining them, and a few approaches were presented to implement this gear manufacturing
method. However, machining helical gears with crowning or other modifications has been little studied. This paper
proposes an accurate method to manufacture helical gears with crowning modifications using a standard 5-axis
CNC machine tool. As gear roughing process, milling using an end mill was selected, where the tool movement
follows the generation principle. By incorporating crowning modifications into the tool’s movement, an accurate
tool path generation method was developed. A CAM software written in C++ was developed to generate,
visualize, and simulate the tool path for machining the gear according to user-defined parameters. The tool path
was subsequently post-processed into NC code to run on a CNC machine. To validate the generated NC code, an
internal helical gear with crowning modification was machined on a conventional 5-axis CNC machine. The
machining results confirmed that the proposed method is feasible. The machined helical gears will be measured
using optical and tactile CMMs to determine their deviation parameters.
ISBN: 978-1-64353-110-6
21FTM17. Holistic Evaluation of Involute Gears

Author(s): Anita Przyklenk, Martin Stein, Tom Reavie, Robert Frazer
The geometry measurement of involute gears is a key step within modelling, manufacturing, and performance
evaluation to assure the delivery of high performance and cost-effective gears and gearboxes. Current challenges
in manufacturing metrology can be summarized in five keywords: fast, accurate, reliable, flexible, and holistic.
Moreover, modern non-generative production methods such as five-axis milling may need different inspection
strategies for reliable quality assurance.
Standardized strategies refer to the most relevant 2D-sections, single helix, and profile line inspection, which has
been state of the art for many decades. These methods are still relevant and continue to deliver high performance
gears, but other options are becoming available. Modern coordinate metrology systems such as CMMs or GMMs
gather holistic information about dimension and surface form of gears with high point density and accuracy in a
short time. Currently, however, we do not know how to use this holistic information.
This paper introduces a 3D evaluation strategy for cylindrical involute gears used at Physikalisch-Technische
Bundesanstalt. The focus is on describing the holistic evaluation of synthetic and measured data. Considering the
complete gear surface in one common model allows us to a) determine deviations along the whole flank, b) obtain
more relevant and stable geometrical fitting parameters, c) find correlations between gear fitting parameters and
d) properly understand possible manufacturing errors.
The paper also shows how Newcastle University’s Design Unit used holistic evaluated data to investigate gear
surface harmonic analysis methods. Harmonic analysis of 2D profile and helix measurement data is routinely used
by some industries to control gear noise and characterize machine tool performance, but the evaluation of 3D

surface measurement data has not been investigated. A review of some candidate methods using synthetic and
measured data is presented and some of the challenges interpreting the results is discussed.
ISBN: 978-1-64353-111-3
21FTM18. Enhanced Distortion Control – ISO Class 8 Gears After Case Hardening
Author(s): Volker Heuer, David Bolton, Jochen Friedel
Controlling distortion during the case-hardening process is of key importance when manufacturing gears. By
effective control of distortion and the variation of distortion, significant costs in post heat treatment machining
processes can be avoided. Especially for E-drive gears such as Internal Ring gears or Final Drive Ring gears
significant cost-savings can be achieved.
If distortion is controlled in such manner that ISO class 8 is guaranteed after case hardening, the grinding
operation gets obsolete, and parts may be honed only.
The combination of Low-Pressure Carburizing (LPC) and High-Pressure Gas Quenching (HPGQ) offers the
potential to provide better control of distortion compared to other process-combinations such as Atmospheric
Carburizing with Oil Quenching.
This paper analyses distortion values of gear components from a planetary set of a six-speed automatic
transmission over a long period of time. The gears were analyzed in terms of circularity, helix average and helix
variation. It is demonstrated that distortion data stays stable and predictable even over a long period of time when
applying optimized heat treatment process parameters and if the process-steps in the manufacturing chain before
heat treatment are frozen and robust.
When combining this heat treatment technology with appropriate geometrical inspection, this will result in
guaranteed ISO class 8 geometry after heat treatment.
The paper gives directions how this goal can be achieved by combining an advanced heat treatment process with
advanced gear inspection technology.
ISBN: 978-1-64353-112-0
21FTM19. Tooth Root Bending Strength of Shot-Peened Gears Made of High-Purity Steels up to the VHCF
Range
Author(s): Daniel Fuchs, Thomas Tobie, and Karsten Stahl
The load capacity calculations for gears according to standardized methods, like AGMA 2001-D04 or ISO 6336,
are intentionally conservative to ensure broad applicability in industrial practice. However, due to new applications
and higher requirements, more detailed design calculations are nowadays often necessary in order to use
possible strength potentials. For example, in wind power gearboxes long operating lives are necessary and in e-
mobility applications, due to fewer gear stages and higher speeds at the electric motor, there are higher load
cycles per tooth. Hence, higher tooth flank and root load carrying capacities up to the very high cycle fatigue
(VHCF) range are desired for gears. To achieve a higher bending strength in the tooth root area of gears, one
approach is to induce increased compressive residual stresses into the stressed area, e.g. by a shot-peening
process. The drawback is that often there is a change in the crack mechanism. Crack initiation can now occur at
non-metallic inclusions in the steel matrix.
For that reason, the working hypothesis of this publication is: the higher the cleanliness the fewer the non-metallic
inclusions in the material and therefore the higher the tooth root capacity of case-hardened, shot-peened gears.
This working hypothesis is verified with tests on FZG back-to-back test rigs up to the very high cycle fatigue
(VHCF) range. The test gear variants were manufactured from steels with different degrees of cleanliness. The
gears were also examined metallographically, with a special focus on the residual stress state in the tooth root
area. As a result, it could be shown that with a higher degree of cleanliness, higher tooth root load carrying
capacities up to a higher number of load cycles are possible even taking the different crack mechanism into
account.
ISBN: 978-1-64353-113-7
21FTM20. 4D Quench – Taking Aerospace to New Heights

Author(s): Thomas Hart
When providing heat treatment for aerospace gears and bearing components, manufacturers are traditionally left
with three choices for thermal processing: continuous flow atmospheric furnaces with press quenching in oil, or
batch heat treatment in both vacuum and atmospheric furnaces with quenching in oil (or high-pressure gas, as in
vacuum). All three techniques differ in benefits and disadvantages associated with geometric distortion,
environmental impact and safety concerns.

A single-piece flow (SPF) vacuum heat treatment furnace with the capability to provide high pressure contour gas
quenching to a single piece or “4D Quench” (4DQ) provides continuous flow heat treatment with low geometric
distortion, environmental impact and personal safety concerns. This system has the flexibility of operating in a
batch style work cell or it can be sized up and inserted in a continuous work cell, operating without human
interference. 4DQ technology equals the speed of an oil quench and the cooling gas nozzle profile can be
optimized based on actual part geometry. By controlling the direction of the cooling gas spray with part rotation,
manufacturers now have the ability to control how fast or slow a part section cools providing a better quench. With
this improved uniformity, larger and previously pressed quenched parts can now be processed in a 4DQ system.
SPF vacuum heat treating system will thermally process and quench every part the same way, in the same
position, with the same timing, one by one. All components undergo the same process parameters, producing
consistent and high-quality results for an entire part series. With SPF vacuum heat treatment, aerospace gear and
bearing manufacturers can safely and environmentally friendly output identically processed and uniform
components while reducing geometric distortion of their heat-treated components. This paper will also summarize
a half decade’s worth of research associated to SPF with 4DQ Vacuum Heat Treatment.
ISBN: 978-1-64353-114-4
2020 PAPERS
20FTM01. Quasi-Static Transmission Error Behavior Under the Composite Effects of Temperature and Load
Author(s): Aitor Arana, Jon Larrañaga, Ibai Ulacia, Mikel Izquierdo, & Miren Larrañaga
Current demands for enhanced rotational speed in electric vehicle transmissions, aeronautical gearboxes and
industrial machinery is known to affect the thermal behavior of mechanical parts by increasing their steady-state
temperature. In geared transmissions, such condition is detrimental as the lubricating film is reduced thus
increasing failure probability, furthermore, if temperature levels are sufficiently high thermal distortion can affect
mesh behavior.
Scientific literature review has shown that no experimental evidence on the composite effect of temperature and
torque on transmission error exists up to date. Although some authors already pointed out that temperature
influences positioning accuracy, no previous reference to peak to peak behavior has been found and comparisons
to torque effects have not been performed.
In this work, quasi-static transmission error behavior is experimentally analyzed under increased thermo-
mechanical conditions. First, the development of a custom back-to-back test rig is described and test specimen
geometries, operating conditions and measurement procedure are presented. Next, loaded transmission error
tests are carried out in order to validate the expected mechanical behavior and then the influence of temperature
is analyzed by heating up the system in a controlled manner. Composite effect of temperature and load are
studied in terms of backlash, mean level of transmission error and its peak-to-peak value. Finally, experimental
measurements are compared to analytical predictions, results are discussed and conclusions are withdrawn.
It is shown that the effect of temperature and torque coexist in transmission error diagrams. Both parameters have
a significant role in the mean level of transmission error while the influence of torque on peak to peak is prominent
relative to that of temperature. Although the correlation between the change of mean level and that of backlash for
increasing temperatures is clear, peak-to-peak variation due to temperature is not obvious.
ISBN: 978-1-64353-079-6
20FTM02. A Comparison of an Analytical and FEA Approach in Determining Thermal Lead Correction for
High Speed Gears
Author(s): Andreas Beinstingel, Burkard Pinnekamp, Michael Heider, Daniel Stierli, & Steffen Marburg
Especially for high-speed applications, gears of large dimensions and high power density are used. Temperature
distribution in those rotors is much different in operation as compared to manufacturing. Therefore, the tooth
contact as it can be validated by blue ink during assembly is not only affected by distortion and bending under
load but also by non-uniform thermal growth. This influence has often been neglected in the past. As power
density and specific load are continuously increasing over time, for highly sophisticated applications, this influence
should be accounted for with suitable lead modification, as it is demanded by the latest version of API 613.
For many years, RENK has been using empiric methods for thermal lead correction based on measurements and
experience. Lately, the authors carried out complex finite element calculations to numerically investigate the
influence of temperature distribution on tooth contact. This kind of detailed finite element modeling for tooth
contact analyses requires a high effort with respect to FE meshing as well as extended computation time.
Therefore, the numerical method was further enhanced. As a result, a simplified approach for quick and reliable
heat analyses for thermal lead correction of high-speed gears was developed. The paper describes the theoretical
background and gives a comparison of the results with the different calculation approaches.

ISBN: 978-1-64353-080-2
20FTM03. Validation of a Generalized Formulation for Load Sharing Behavior in Epicyclic Gears for Wind
Turbines
Author(s): Yi Guo, & Jonathan Keller
In an ideal epicyclic gear set, every parallel gear path transmits the same amount of torque. However, it is well
known that certain manufacturing variations result in unequal load sharing between the parallel gear paths.
Previous works have developed and validated a general closed-form analytical model of this phenomenon that
describes the load sharing characteristics of epicyclic gear sets from three to six planets at any torque level. More
recently, this analytical model has been reformulated to include the effects of gravity, carrier bearing clearance,
and external applied moments, all of which are relevant to most gearboxes and their mounting configuration in
horizontal-axis wind turbines. In this paper, the reformulated model is compared to load measurements collected
from two similar wind turbine gearboxes with three-planet epicyclic gear sets. The resulting load sharing values
are also compared to the mesh load factor requirements in the AGMA 6006 and IEC 61400-4 wind turbine
gearbox design standards. Load sharing factors as high as 1.16 at extreme rotor moments and 1.08 with no
moment were measured for the gearbox with cylindrical roller bearings, but the load sharing factor remained
below 1.10 for the gearbox with tapered roller bearings. Results show that in the wind turbine application, load
sharing is not equal—even for three-planet systems with a floating central member because of the effects of
gravity, rotor moments, and the resulting relative motions among the epicyclic gear components within the carrier
bearing clearance.
ISBN: 978-1-64353-081-9
20FTM04. Effects of Different Shot Peening Treatments in Combination with a Superfinishing Process on the
Surface Durability of Case-Hardened Gears
Author(s): Dominik Kratzer, Johannes König, Thomas Tobie, & Karsten Stahl
Modern gearbox designs set increasing requirements on the surface durability of gears in light of calls for
downsizing and performance optimization. Using additional manufacturing processes is one way to tackle these
challenges. The increase in the compressive residual stress state due to shot peening and the decrease in the
roughness of the gear flank surface due to superfinishing processes are two possible measures. While there have
been extensive scientific studies in the past on the positive effects of shot peening and superfinishing, a detailed
quantification of a calculation model of these two effects has not been subject to in-depth investigation yet. To
address this gap in knowledge, a study was carried out to examine and evaluate different peening processes and
the resulting residual stress profiles in combination with a superfinishing process. Experimental investigations
showed significant differences in the gear flank load-carrying capacity due to the different surface treatments. In
addition, a significant reduction in micropitting appearance was observed due to the superfinishing process, while
the increased compressive residual stresses due to shot peening showed no significant influence on the
development of micropitting. By correlating the pitting durability from the experimental investigations with existing
calculation methods, it was possible to extend the surface factor ZR from ISO 6336 to a wider range of roughness
values as well as to introduce a new factor ZS for different shot peening treatments. Based on the results of this
paper, the positive effects of different shot peening processes as well as superfinishing processes can be taken
into account for gearbox design and rating processes.
ISBN: 978-1-64353-082-6
20FTM05. Gear Sliding Losses

Author(s): Parviz Merati, John Bair, Carlos Wink, & Farrukh Qureshi
Gearbox efficiency is becoming increasingly important for vehicle manufacturers to help achieve their overall fuel
savings goals. Enhancing gearbox efficiency is also critical in saving the up-front cost and overall unreliability of
gearbox cooling. It is well known that at high power levels, gear sliding losses dominate the overall gearbox
losses. Therefore, accurately predicting frictional losses is critical for increasing overall gearbox efficiency.
Previous work by these authors has shown that available closed-form calculations do not provide the range of
important inputs or accuracy required to perform reliable design estimates of the sliding losses that are so
important to the thermal and efficiency characteristics of the gearbox. This paper documents an approach used to
incorporate the effect of lubrication characteristics, gear geometry, surface finish, and operating conditions into an
algorithm that accurately predicts sliding losses over a range of operating conditions for a standard set of gears.
This study provides a method for accurately calculating gear sliding losses based on all the important design
variables early in the process, so that efficiency can be more easily assured. The methodology developed for
simple contacts is used to predict gear sliding losses for much more complicated cases of spur and helical gears,
where load and rolling and sliding speed of the contact patch varies at each roll angle during the mesh cycle.
ISBN: 978-1-64353-083-3
20FTM06. A New Approach for the Calculation of Worm Shaft Deflection in Worm and Crossed Helical Gear
Drives
Author(s): Philipp Norgauer, Gerhard Keinprecht, Michael Hein, & Karsten Stahl

Worm gear drives are characterized by a simple design, which allows the realization of a high gear ratio within
one stage. Furthermore, they are characterized by low vibration and noise behavior. For these reasons, they are
used both as power transmissions and servo drives in various drive solutions. The allowable load and the lifetime
of the gearbox is usually limited by wear on the softer worm wheel. An influence factor on the wear as well as the
NVH behavior of worm gear drives represents the stiffness and the associated worm shaft deflection.
According to the current state of the art, the worm shaft deflection can be calculated accord-ing to AGMA 6022,
DIN 3996 and ISO/TR 14521.
In this paper, the current calculation status for worm shaft deflection is discussed. The underlying experimental
results for the calculation of the worm shaft deflection according to DIN 3996 and ISO/TR 14521 are analyzed. A
new approach for the worm shaft deflection calculation is developed. Therefor an analytical model for the bending
stiffness of a worm shaft is developed. The model was validated through various FEM simulations. As a result, a
new calculation method for the equivalent bending diameter of a worm as well as the formulae for the calculation
of the worm shaft deflection are presented.
The developed calculation method details the current state of the art, thus providing a basis for more optimized
worm gear design. Furthermore, with this calculation it is now possible to calculate the bending stiffness of
overhung worm shafts as well as worms of reduced tooth thick-ness, which are usually used in crossed helical
gear boxes.
The new calculation method is presented within this paper and compared to the current state of the art for
calculating the worm shaft deflection according to AGMA 6022, DIN 3996 and ISO/TR 14521.
ISBN: 978-1-64353-084-0
20FTM07. Case Study of ISO/TS 6336-22 Micropitting Calculation

Author(s): Robin Olson, Mark Michaud, & Jonathan Keller
ISO/TS 6336-22 (Calculation of load capacity of spur and helical gears — Part 22: Calculation of micropitting load
capacity) is the ISO technical specification containing a proposal for a calculation for the risk of micropitting in
gear sets. This document was originally published in 2010 as ISO/TR 14179-1 and added to the ISO 6336 suite of
documents in 2018. It assesses micropitting risk through a safety factor that is calculated as the minimum specific
film thickness in the contact zone divided by a permissible specific film thickness. A sliding parameter is used to
adjust the film thickness in the contact zone to the region of highest sliding, which is where micropitting has been
observed. The permissible specific film thickness is best determined through experience or testing, but there is an
option to estimate it based on the lubricant’s failure load stage in FVA-FZG micropitting testing. This paper is a
case study to compare the results of the calculation to applications that have experienced micropitting in the field.
For these examples, the method does not predict micropitting because of limitations in the Method B formulation.
ISBN: 978-1-64353-085-7
20FTM08. Service Life of Cylindrical and Bevel Gears Under Variable Load and Stresses
Author(s): Daniel Vietze, Josef Pellkofer, Michael Hein, & Karsten Stahl
Transmissions are usually loaded by variable external loads under real operating conditions. The decisive load for
a gearbox is in most cases the applied torque. Commonly used allowable stress numbers σHlim/Flim (ISO) or
σHP/FP (AGMA) for calculating the load carrying capacity of cylindrical, bevel and hypoid gears are usually
derived from single stage tests carried out on pulsators or back-to-back test rigs. Variable loads can be
considered in the calculation of the load carrying capacity by using application factors, overload factors or more
complex standards like ISO 6336-6, which was recently revised. In case of variable loads, the calculation of the
load carrying capacity of gears is quite different to bearings. According to ISO 6336-6, a safety factor is
determined for gears and according to ISO 281, a service life is determined for bearings, respectively. Whereas all
of these calculation methods only consider a global safety or lifetime, continuously progressing failures like
micropitting or wear can – especially on bevel and hypoid gears – also lead to locally varying stresses even if only
a constant external load is applied.
This paper is intended to give a brief overview of currently applied methods to consider variable loads in the
design process of cylindrical as well as bevel and hypoid gears. Therefore, the scope of application of these
methods is shown and critically analyzed for the damage mechanisms pitting, tooth root breakage and tooth flank
fracture. Especially the changes made in the revised version of ISO 6336-6 are shown in detail. Furthermore, the
influence of locally changing stresses on the pitting load carrying capacity is explained on bevel and hypoid gears.
A method to assess such influence is shown for constant external loads.
ISBN: 978-1-64353-086-4

20FTM09. Single Tooth Bending Fatigue Testing at any R Ratio
Author(s): Matthew Wagner, Aaron Isaacson, Kevin Knox, &Thomas Hylton
Single tooth bending fatigue (STBF) testing has long been used as a simple and cost effective alternative to
running gear bending fatigue tests. In typical STBF testing, the test tooth root fillet is subjected to a cyclic tensile
load until bending failure occurs, while the test load is reacted with an opposing tooth along the line of action. This
results in a rather simple fixture design, however the typical STBF fixture design does not allow for any reversal of
the loading in order to stress the tooth roots in compression. The test loads for this type of test vary from a
maximum tensile value to a percentage of the maximum, resulting in a positive R-ratio (ratio of minimum to
maximum load).
It is well known that the root area of a gear tooth is subject to both tensile and compressive stresses as the tooth
approaches and subsequently meshes with mating teeth. For a single pair of meshing gears, the loading
experienced by the root fillet results in a slightly negative R-ratio in practice. For idler or epicyclic planet gears, the
loading is fully reversed and the extreme case of a load ratio of R = -1.0 occurs.
The Single Tooth Reversible Bending Fatigue (STRBF) test outlined herein overcomes previous limitations by
allowing compressive loads to be applied to the test tooth root in any magnitude in conjunction with the typical
tensile loads. This test setup involves three teeth of the test gear, with the upper and lower teeth providing the
reactions in the up and down load directions and the test tooth being subject to test loads in both directions. Any
R-ratio applicable to gear bending fatigue testing up to and including fully reversed loading (1 > R ≥ -1) is
possible. Non-dimensional examples of fatigue data from a recently completed fully reversed testing program are
shown.
ISBN: 978-1-64353-087-1
20FTM10. Analysis of the Operational Behavior of a High-Speed Planetary Gear Stage for Electric Heavy-Duty
Trucks in Multi-Body Simulation
Author(s): Christian Westphal, Jens Brimmers, & Christian Brecher
Stricter emission limits accelerate the development of electric trucks, especially for urban distribution traffic. The
use of electric motors instead of diesel engines confronts gearbox development with the challenge of higher
engine speeds and higher requirements on transmission acoustics. Planetary gearboxes are often used for this
purpose, as they allow high transmission ratios in reduced assembly space.
Dynamic multi-body simulation (MBS) is used for detailed dynamic modeling of drive trains. The interaction of
gears and shafts in planetary gearboxes requires, especially for NVH-analysis, advanced simulation methods due
to the sophisticated kinematics and the more sensitive displacement behavior. Dynamic simulation methods for
cylindrical gears usually describe the tooth contact based on analytical equations or consider only one rotational
degree of freedom, which leads to uncertainties in the simulation results. Misalignments are therefore, either
simplified or not considered at all. The authors developed a method that combines the advantages of the quasi-
static FE-based tooth contact analysis with the advantages of an integrated approach in the MBS.
In this paper the operational behavior of a high-speed planetary gear stage for electric heavy-duty trucks is
analyzed in dynamic MBS. The method for the tooth contact analysis in the MBS is used for the simulation of
planetary gearboxes. Different mesh sequences and model configurations for planetary gearboxes are compared
and the effects on the operational behavior are evaluated. In addition to the dynamic transmission error, the
dynamic tooth flank pressures are analyzed. Furthermore, dynamic misalignments in the tooth contact and the
load sharing behavior in dynamic operating conditions are evaluated. In the simulation, the misalignment of the
gears is directly taken into account by means of a penetration calculation in every time step. The presented
method allows a well-founded prediction of the operational behavior of planetary gear stages, considering the
dynamic interaction of the components.
ISBN: 978-1-64353-088-8

2019 PAPERS
19FTM01. Electric Vehicle Transmission with Hypoid Gearset
Author: Hermann Stadtfeld, and Hanspeter Dinner
Compact electric vehicles require a cost effective and compact solution for the location of the electric motor and
the transmission. Yes, even small electric vehicles today require a transmission, if the maximal possible motor
efficiency has to be available in the majority of drive conditions. Most of the existing solutions for front wheel
driven electric vehicles place the eMotor and the transmission inline between the front wheels. This results in an
asymmetric weight distribution as well as motor heat radiation towards one of the two front wheels.
The paper presents a new design concept which utilizes a super reduction hypoid with a ratio between 7 and 15.
The hypoid gearset rotates the eMotor away from the limited space between the front wheels and delivers a
symmetrical weight distribution as well as a heat radiation away from the wheels. Due to the preferred one stage
reduction, the proposed eDrive transmission is very compact and provides multiple possibilities for an optimal
vehicle component packaging. The paper will discuss the variety of transmission designs, orientations and
locations. The compact design as well as the fact that a one stage transmission minimizes the number of shafts,
bearings and gears allows for a cost effective eDrive manufacture.
Design and dimensioning of the transmission and its components was done with the KISSsoft system. In order to
utilize a super reduction hypoid gearset for an automotive eDrive, not only the efficiency has to be high, but
equally important is a high back driving efficiency. A good back driving efficiency allows recuperating maximal
amounts of electrical energy for battery re-charging. To allow the optimization of the back driving efficiency the
coefficient CBD (Back Driving Coefficient) is proposed. Furthermore, fundamental changes of the SRH geometry
versus conventional hypoid gears had to be developed in order to achieve desirable values for CBD.
ISBN: 978-1-64353-040-6
19FTM02. Misalignment Compensation Spline Design

Author: Davide Marano, Mariano Lorenzini, Luca Mastrandrea, Francesco Pulvirenti, Massimiliano Turci, and
Nicolas Fillault
Shaft misalignment is a significant problem in the design of spline joint transmissions. Involute splines with flank
line crowned teeth are a solution to compensate shaft parallel misalignments avoiding interferences between shaft
and hub teeth. A precise determination of the influence of misalignment on spline load capacity can be performed
by FEM or other powerful numerical simulation.
In this study a geometrical model of crowned spline joint for misalignment compensation is proposed. Flank line
crowning is determined as a function of shaft misalignment and the minimum theoretical circumferential backlash.
The proposed approach is adopted for the design of a spline joint, part of a high-performance automotive
driveline. Finite element simulation has been performed to determine the spline loaded tooth contact pattern and
optimize the theoretical crowning value. Experimental results are in good agreement with simulations.
Keywords: Power transmission, Spline joint, Misalignment, Crowning, Pitch deviation, Analytical modelling,
Concentration factor, Strength calculations.
ISBN: 978-1-64353-041-3
19FTM03. Spline Centering, Piloting, and Toggle: Torsional Stiffness, Shaft Bending, and Centering of
Moment Loads
Author: Stephen McKenny and Dustin Eseltine
Common practice for a splined joint is to assume that the load is theoretically transmitted along the entire length of
the tooth face, but several factors, including axial spline length and the ratio of hub to shaft torsional stiffness, can
impact how the load is distributed along the tooth face. Previous papers have considered the effect of pure torque
and combined torque plus radial load, but few have described the impact of splines loaded with torque plus both
moment and radial load.
A spline with short axial length, if sufficient torque is applied, can center a hub that is subjected to a radial load. A
sufficiently long spline may be able to center a hub that has both radial and moment loads acting upon it – but if
the hub torsional stiffness is much higher than the shaft stiffness there may not be sufficient torque transfer at the
far end of the spline to center the hub against its moment load.
This paper describes the behavior of spline interfaces in piloted (radially offset), full toggle, half toggle, and
centered alignment states. These alignment states are created by a combination of part geometry and load
conditions. Part geometry includes the influence of torsional stiffness of the hub relative to the shaft stiffness, and
spline length to diameter ratio. Load conditions considered include combinations of torque, radial load, and

moment load. Splines with a large length-to-diameter ratio are modeled as a set of two short splines to describe
their alignment state. The amount of misalignment allowed in piloted, full toggle, and half toggle is calculated, and
a chart of misalignment load factor vs. torque and stiffness ratio (hub to shaft) is provided.
ISBN: 978-1-64353-042-0
19FTM04. Optimal Polymer Gear Design: Metal-to-Plastic Conversion

Author: Alexander Kapelevich
Recent achievements in polymer development have inspired a tendency to replace metal gears with plastic ones
in many moderately loaded mass-produced gear drives. This metal-to-plastic conversion takes advantage of the
benefits of plastic gears, such as low production cost, reduced weight and inertia, low noise and vibration, zero
corrosion and electric current conductivity, and the advantages of the injection molding process in producing
complicated multifunctional parts. However, a simple material replacement is insufficient for a successful metal-to-
plastic conversion. Some polymer material limitations — low strength and wear resistance, low thermal
conductivity that reduces maximum operating temperature, sensitivity to operating conditions (temperature and
humidity), limited injection molding process accuracy — must be compensated for by innovative gear design.
Unlike machined metal gears, which are typically constrained by standard tooth proportions and hobbing rack
generation technology, a polymer gear injection molding process allows for a deep optimization of gear tooth
geometry. Such optimization of plastic gears for a particular custom application, essential for a metal-to-plastic
conversion, is comprehensively covered by the Direct Gear Design method.
The article describes the optimal selection of operating pressure angle and contact ratio to maximize load sharing
between contacting tooth pairs, and root fillet optimization to minimize root stress concentration.
The article presents a numerical example of a metal-to-plastic conversion, comparing a standard steel gear pair to
its replacement polymer gears, whose optimal design utilizes all the advantages of polymer materials and
compensates for their limitations. It outlines basic guidelines for optimal polymer gear design.
ISBN: 978-1-64353-043-7
19FTM05. Design of a Double Spiral Bevel Gearset

Author: Horácio Albertini, Thiago Cardoso, Márcio de Souza, and Diego Alves
It is known that bevel gears are used to transmit rotary motion and torque between intersected axes in case there
is no possibility of using a parallel axis gearset, which are of simpler manufacture. Their most common geometries
are straight bevel gear, spiral bevel gear and helical bevel gear (skew bevel gear), and all these types of gearset
subject the bearings to three types of force vectors, namely: axial, radial and tangential loads which consequently
influence their dimensioning. Therefore, any attempt to minimize radial and axial loads will lead to a more
economical solution for the bearing’s sizes.
Thus, the present study aims the development of a conical gearset designed with a double spiral, expecting that
radial and axial loads decrease and hence impacts the design of power transmission units, reducing the stresses
acting on the bearings, and consequently their weights.
Similar geometry was proposed in the past (a herringbone face gear was manufactured by Citroen); however, the
manufacturing processes of that time did not allow such geometry to be developed and applied on a large scale
since, in most cases, casting processes were used without a subsequent surface finishing process. Nevertheless,
with the development of CNC machines with 5 or more axes and additive manufacturing processes, the design of
double spiral bevel gears becomes feasible with the possibility of being applied in a wide range of applications.
ISBN: 978-1-64353-044-4
19FTM06. Specific Dynamic Behavior of Planetary Gears

Author: Burkhard. Pinnekamp, Michael Heider, and Andreas Beinstingel
Gear noise is a very important contribution to the overall performance of power transmission systems. The actual
gear mesh is the most decisive criterion for noise generation with two aspects: a) impact of gears getting into
mesh with the previous mesh being deflected under load resulting in premature mesh begin and/or mesh
interference and b) mesh stiffness variation and hereby uneven angular velocity and torsional vibration excitation.
Optimized lead and profile modification as well as high values for profile and overlap ratios are basic measures to
reduce noise excitation.
There are specific conditions for the multiple gear meshes in planetary gear systems. Focusing on the sun pinion,
it can be distinguished between simultaneous and sequential meshing. Many planetary gears are spur gears with
higher excitation level than helical gears due to the lack of overlap ratio.
Theory of noise generation in a gear mesh and the specific application on planetary gear systems are described in
this paper. The results are illustrated by an example with test bench measurements.
ISBN: 978-1-64353-045-1

19FTM07. Phase Management as a Strategy to Reduce Gear Whine in Idler Gear Sets
Author: Robert White and Pravin Patil
Gear whine is controlled by managing transmission error (TE). Transmission error forces in the mesh are reacted
by the bearings supporting the shafts. These forces dynamically excite the housing and cause its walls to vibrate.
The walls couple with the air, making pressure waves that travel to our ears which we hear as sound. Reducing
the dynamic forces on the housing reduces noise. In idler gear sets, we have an opportunity to affect gear whine
by phasing the meshes. Phase is determined by the number of teeth and tooth thickness of the idler. The TE
forces acting on the idler from its two meshes add vectorially and sweep out an ellipse as the gears are advanced
one tooth. The size of the ellipse (magnitude of force) is related to the noise generated by the gearbox. By cleverly
selecting the number of teeth on the idlers, their tooth thicknesses and the idler location, the forces from
transmission error force vectors that must be reacted by the idler bearings can be substantially reduced, thereby
reducing the excitation on the gearbox that causes noise.
ISBN: 978-1-64353-046-8
19FTM08. Leveraging the Complementary Strengths of Orbitless and Planetary Drives
Author: Leo Stocco
An Orbitless drive is a novel fixed-ratio epi-cyclic drive which includes a second carrier in place of a ring gear. It
has been shown to have superior efficiency to a Planetary drive and is shown here to produce less vibration and
noise at the expense of reduced torque capacity and ratio. A prototype 16mm Orbitless drive is constructed and
compared to an off-the-shelf Planetary drive. Vibrations that occur at the Planetary tooth engagement frequency
are absent from the Orbitless drive. A higher quality 32mm Orbitless prototype is evaluated in a multi-stage
environment in both a stand-alone and multi-stage configuration. It is shown that sound levels are reduced, sound
quality is improved, and it is concluded that an Orbitless primary stage may be mated with conventional
technologies to minimize NVH levels in multi-stage gear drives.
ISBN: 978-1-64353-047-5
19FTM09. Reduction of the Tonality of Gear Noise by Application of Topography Scattering for Ground Bevel
Gears
Author: Marcel Kasten, Christian Brecher, Christoph Löpenhaus, Andreas Lemmer, Werner Bläse, and Rolf
Schalaster
The noise behavior of transmission is mainly caused by the excitation in the gear mesh. The standardized design
and calculation methods for gears concentrate on the reduction of the excitation level. However, often the physical
noise characteristics do not conform with the human noise perception. Thus, gear design rules and guidelines are
required that are able to rate the excitation according to the perception. The effect of the targeted topography
scatter generally described is the reduction of the gear mesh amplitudes with an increase of the background
noise. In this report, the noise behavior of bevel gears is investigated with a targeted topography scattering. The
excitation and noise behavior is analyzed from the excitation in tooth contact by transmission error measurements
up to noise emission in the form of airborne noise. Finally, it is the objective to evaluate the impact of individual
topography scattering on the dynamic noise behavior. The analysis of the noise behavior of two variants are
compared regarding the difference in psychoacoustic parameters such as loudness and tonality. The potentials of
the topography deviation for the optimization of ground bevel gears in terms of tonality reduction will be shown by
test results. A test fixture for the evaluation of the operational behavior under loaded and dynamic conditions will
be used. Finally, the method is applied to a vehicle transmission and the noise behavior on the test bench and
inside of the vehicle is investigated and evaluated.
ISBN: 978-1-64353-048-2
19FTM10. Computing Gear Sliding Losses

Author: Caleb Gurd, Carlos Wink, John Bair, and Claudia Fajardo
Accurately predicting frictional losses is critical for increasing gearbox efficiency. Whereas several empirical
algorithms are available for numerically predicting coefficient of friction and gear sliding losses, a systematic
evaluation of these is necessary to establish their accuracy and range of applicability. This paper evaluates nine
different algorithms available in the literature for determining coefficient of friction and calculating gear sliding loss,
and their applicability to commercial vehicle transmissions. Power loss results are compared initially to the
experimental data from a standard FZG gear set, and then to two transmissions with helical gears for a range of
operating torque, speed, and temperature. The differences between predictions and measurements are discussed
for each algorithm evaluated and a recommendation is presented for improved accuracy within the application
range investigated. The findings of this study might help gear engineers select the appropriate algorithm for
calculating gear sliding losses, and ultimately increase gearbox efficiency.
ISBN: 978-1-64353-049-9

19FTM11. Opportunities of Efficiency Improvement by the Use of Hydro Lubricants
Author: Matthias Pfadt, Elena von Hörsten, and Balasubramaniam Vendudusamy
The majority of industrial lubricants are still based on mineral oils due primarily to low cost and good compatibility
with other oils, although different base fluid types exist in the market. However, despite their widespread use,
conventional lubricants reach functional limits in various scenarios. In addition to the limitations of natural
resources, their safe and environmentally sound handling, use and disposal often require considerable efforts. At
the same time, industrial operators’ expectations towards innovative specialty lubricants are increasing. They
range from operational and food safety to biodegradability, longer life cycles and reduced emissions and energy
consumption.
While searching for a material that meets all of these general and branch-specific requirements, water is a
visionary but yet an obvious raw material available worldwide, non-toxic, non-combustible. The benefits are clear,
but some challenges include its low viscosity, evaporation, freezing point, corrosiveness and sensitivity against
microbiological growth.
Hydro Lubricants unfold their innovative traits by using water either as a base oil or as an additive, hence the
name ‘‘Hydro Lubes’’. Initial results indicate that it is a promising technology with a great potential to deliver high
performance; some include high thermal and electric conductivity, superlow friction and good load carrying
capacity on the FZG four-square test machine. Some key challenges of Hydro Lubricants like pour point,
corrosion protection and microbiological growth have been solved by proper and advanced formulation. With the
wide range of benefits, different Hydro Lubricants have been developed for applications like gears and
hydrodynamic bearings.
Hydro Lubricants offer a more sustainable solution and are potential candidates for a wide range of industrial
applications that particularly demand for huge energy savings.
ISBN: 978-1-64353-050-5
19FTM12. Evaluation of Steel Cleanliness By Extreme Value Statistics and its Correlation With Fatigue
Performance
Author: Trishita Roy, Cassie L. Smith, Nikhil Deo, Carlos Wink, and Jason Carroll
Nonmetallic inclusions, primarily oxides play a significant role in the fatigue performance of components such as
bearings and gears that undergo fatigue loading. This leads to an increased demand for cleaner steel for longer-
life applications. Due to the advances made in steel making processes in the past decades, the oxygen level as
well as inclusion size and distribution have been brought under remarkable control enabling production of high-
quality steel. Consequently, the earlier inclusion rating methods such as ASTM A534, ASTM E-45 that use a
comparison with standard micrographs are insufficient to render an effective comparison of cleanliness of steels
from different heats or suppliers, especially for the cleaner heats. It thus becomes imperative to find a reliable
method to predict the size of the largest inclusions present in a steel volume and to further correlate it with the
fatigue limit of steel. This is another limitation of the existing inclusion rating methods. Extreme value analysis is a
method that can surmount these limitations and it comprises of examination of a small area of steel by Optical or
Scanning Electron Microscopy to predict the maximum size of inclusions which may inhabit a larger volume of
steel.
In this work, the effect of inclusion size distribution on fatigue performance is investigated from the experimental
data obtained using ultrasonic fatigue testing. Extreme value analysis is used to predict the characteristic size of
the largest inclusion based on the metallographic observations on polished surfaces and this inclusion size is then
correlated with the fatigue limit measured by ultrasonic fatigue testing, making use of the Murakami approach.
ISBN: 978-1-64353-051-2
19FTM13. Tooth Root Testing of Steels with High Cleanliness

Author: Moritz Trippe, Christoph Löpenhaus, Christian Brecher, Lily Kamjou, and Elias Löthman
The power density of gearboxes is continuously increased through different research activities. Besides new
material developments, steel cleanliness comes to the forefront in order to meet future requirements regarding
load carrying capacity of gears. The experimental quantification of load carrying potentials for high quality steels is
the basis for introducing cleanliness as a design parameter.
In this paper, investigations on the tooth root load carrying capacity of steels with different cleanliness levels are
presented. The investigations are carried out on a pulsator test rig with a standardized FZG-C gear geometry. To
determine and compare the different behaviors of the tested steels, correct force application in the test rig needs
to be ensured. By this, it is possible to clearly separate the endurance strength for different cleanliness levels
within the same steel grade composition.
For the pulsator testing, an approach for checking and ensuring correct clamping of the gears is presented. Using
this procedure, endurance tests on conventionally manufactured gears with different cleanliness levels are carried
out. Resulting mean values of the tooth root strength as well as scattering of test results is evaluated, and the

influence of higher cleanliness on an increasing mean value and decreasing scattering is proved. The confidence
level of the mean value is discussed regarding the overall number of tests.
As a conclusion, the impact of steel cleanliness on increasing endurance strength and decreasing scattering is
separated from manufacturing and testing influences. A higher level of cleanliness takes into account the
influence of the occurring failure mechanisms. Especially for applications with a high manufacturing and surface
quality, high quality steels show a high potential for increasing the load carrying capacity and thereby the power
density of the gearbox.
ISBN: 978-1-64353-052-9
19FTM14. 4D High Pressure Gas Quenching - A Leap in Performance vs. Press Quenching
Author: Thomas Hart and Dr. Maciej Korecki
Thermal processing and quenching of steels for hardening is a well-established practice performed by various
techniques over the centuries. A common thread has been the unpredictable nature of the size change during the
quenching process, which is known as dimensional change or distortion. Material distortion is the undesired trade-
off between the development of proper mechanical property and the necessity of rapidly quenching the material
from elevated temperatures into a quenching media (i.e. brine, water, polymer, oil, gas, molten salt, etc.). Due to
this compromise, users have been attempting to reduce part distortion because once a component is hardened, it
becomes very difficult and costly to remove excess material or form the part back into its original shape.
When one looks at the bearing and gearing industries, materials typically are hardened via austenitizing and
quenching. Not only do these components require high hardness and wear/corrosion resistance, they also require
high dimensional precision to tight tolerances as well as repeatability of results. One of the most common way to
reduce material distortion when quenching is a method by which a heated component is placed in a special fixture
and a steady force is applied to the component, which allow the part to resist material deformation when the
quenching media is applied. This method of quenching is known as “press quenching” and requires specialized
equipment, manual or robotic handling, custom die sets and high maintenance as well as being operator
dependent to achieve consistent results.
It is well known that machining after heat treatment is one of the most costly and difficult tasks to complete in the
entire manufacturing life cycle. This is why an extreme amount of engineering is devoted to the prevention of
distortion of a component to ease the post heat treatment machining operations. With the ever prevailing desire to
lower the cost of raw materials and still maintain proper mechanical performance, extreme amounts of pressure
are applied to the heat treatment process to bring up the quality level of the low cost steel. When using these low
quality steels, they are prone to high levels of distortion during the quenching process, such that they distort more
than the allowable amount and either become too challenging to hard machine or are not able to be used all
together. ~4% of the price for a hardened component is attributed to the removal of post heat treatment material
to so that it meets the finished size requirements. When users can control distortion, they lower the overall cost of
the component.
This paper will introduce the latest achievements in the advancement of distortion control by way of 4D High
Pressure Gas Quenching (HPGQ) versus press quenching. Both processes quench a single part at a time but the
4D HPGQ process does not subject a part to any clamping forces or issues associated with liquid quenching
inconsistencies. The 4D HPGQ process results in every single part being heated and quenched identically the
same at surprisingly low gas pressures thus producing extremely accurate dimensional variation with highly
repeatable results. 4D HPGQ systems are easily integrated into current manufacturing environments and the
process is a revolutionary advance in quenching technology, which has been shown to reduce or even eliminate
the need for expensive & difficult post hardening manufacturing processes.
ISBN: 978-1-64353-053-6
19FTM15. Performance and Properties of a New, Alternative Gear Steel

Author: Lily Kamjou and Joakim Fagerlund
In the ongoing strive for light weighting or power densification, high-performance clean steels are showing a
significant improvement. As a next step, gear steels that combine several properties, are now proving an
interesting alternative. Traditional gear steels achieve their maximum hardness after carburizing and a fast
quench. A fast quench usually results in distortion as the part is unavoidably unsymmetrically cooled/quenched.
For many gear applications, distortion during heat treatment of final component, can add cost and unwanted hard
machining operations. With many components being more sensitive to distortion, especially within electrical
vehicles, where NVH becomes even more important, the potential to reduce distortion from heat treatment can be
essential. With a new steel composition, that hardens by precipitation hardening (aging around 500°C/950F) low
distortion can be attained as a fast quench such as an oil quench is not necessary. This type of steel can be both
nitrided and carburized. Costly hard machining can therefore be reduced due to the low distortion. Other
interesting properties of this new steel that will be presented in this paper are; good mechanical properties at
elevated temperatures and good corrosion and oxidation properties compared to traditional gear steels.
ISBN: 978-1-64353-054-3

19FTM16. Material Properties and Tooth Root Bending Strength of Shot Blasted, Case Carburized Gears with
Alternative Microstructures
Author: Karl Jakob Winkler, Christian Güntner, Thomas Tobie, Karsten Stahl, and Stefan Schurer
Case hardening is one of the most common heat treatment processes for highly loaded components such as
shafts and gears. Due to numerous investigations and according to the material requirements for quality grade
MQ and ME in part 5 of ISO 6336, a microstructure consisting of martensite with less than 30% retained austenite
is favorable for a high load carrying capacity.
A former research project focused on the load carrying capacity of carbonitrided gears with alternative
microstructures. In this research project, the carbonitrided gears with an increased amount of retained austenite of
up to 65% showed a higher tooth flank load capacity than standard case carburized gears. At the same time, the
tooth root bending strength was not influenced in a negative way. The question arises, how different alternative
microstructures influence material properties and thus affect the tooth root bending strength of gears.
This report states the results of current investigations on material properties such as hardness depth profile,
residual stress condition and amount of retained austenite as well as the tooth root bending strength of gear
variants with different alternative microstructures. All gear variants are shot blasted after the heat treatment and
made out of the materials 20MnCr5 and 18CrNiMo7-6.
The tooth root bending strength in the high cycle fatigue regime of these gear variants is not inferior compared to
standard case carburized gears. In the cycle regime of limited life, the tooth root bending strength can be
increased as well as decreased by the alternative microstructures.
As consequence, when regarding the tooth root bending strength, certain alternative microstructures, which are
different to the recommendations of part 5 of the standard ISO 6336, can be tolerated. This means consequently,
that if the tooth root bending strength is tested and acceptable, alternative microstructures can increase the tooth
flank load capacity for shot blasted, case carburized gears.
ISBN: 978-1-64353-055-0
19FTM17. Chamfering of Cylindrical Gears - New Innovative Cutting Solutions for Efficient Gear Production
Author: Gottfried Klein
Cylindrical gear chamfering and deburring is a rather ‘unloved’ process that adds cost but without delivering
readily apparent improvements in gear quality. However, the chamfer process, when performed correctly,
provides significant advantages for downstream handling and processing. This is why manufacturers of
automotive- and truck-sized gears are increasingly exploring new technologies to chamfer their gears.
Two major chamfer technologies are used: forming and cutting. While chamfer rolling is a highly proven forming
process that has been used for decades mainly in mass production, cutting chamfer technologies are of
increasing market interest due to cost reduction and increased quality requirements; especially in dry cutting
conditions.
This paper will cover new chamfer cutting processes: Chamfer Contour Milling and Chamfer Hobbing and
compare them with the existing chamfer roll technology.
Chamfer Contour Milling uses a universal fly cutter tool with indexable carbide inserts. Chamfer angle and
chamfer size depend on programmable machine movements. Therefore, this process provides highest flexibility
for coarse pitch gears – even with different modules, pressure angles or number of teeth.
Chamfer Hobbing has been developed for modern gear production focusing on low tool cost per part with dry
cutting and short cycle times in mass production. As for the left and right gear flank, separate and dedicated
chamfer hobs are used to meet most customer specifications in the market.
By comparing the advantages and limits of the aforementioned chamfer processes in gear production for
workpieces up to 400 mm diameter and module 8 mm, it is possible to select the right process depending on the
specific requirements.
ISBN: 978-1-64353-056-7
19FTM18. Influence of Manufacturing Variations of Spline Couplings on Gear Root and Contact Stress
Author: Hareesh Kurup and Carlos Wink
Involute splines are widely used in mechanical systems to connect power transmitting gears to their supporting
shafts. These splines are as susceptible as gears to manufacturing variations, which change their loading pattern
and may eventually lead to failures. The influence of manufacturing variations of spline teeth on performance and
failure mechanisms of spline couplings is available in the literature. Similarly, the influence of manufacturing
variations of gear teeth on gear tooth stresses, and gear noise has been extensively studied. However, the effects
of manufacturing variations of spline teeth on gear tooth contact, noise, and stresses remain unseen in
publications. This study investigates how manufacturing variations of spline couplings affect gear performance. A

parametric study was done on a spur gear set and a helical gear set to determine the amount of gear mesh
misalignment caused by manufacturing variations of spline teeth. Spline parameters, such as tooth alignment and
spline side fit were considered. The changes in gear contact and bending stress patterns were also investigated.
ISBN: 978-1-64353-057-4
19FTM19. Micro-skiving - (r)evolution of a Known Production Process

Author: Pierre Falbriard, and Hervé Baour
Production of internally toothed gear wheels is possible in many different ways. Different techniques such as
gashing, broaching, wire EDM or shaving make it possible to achieve these profiles. However, skiving seems to
be the optimal solution for reducing production time of this type of gears when large production batches are
required.
This internal gear cutting technique has been known for several years and widely used in the industry for modules
over 0.50 (DP>50).
However, cutting an internal gear with a module below 0.50 (DP>50) is not an easy task. The profile becomes
very small and requires an optimized cutting tool, which can only be manufactured on special grinding machines
that can cope with micron (μm) accuracy.
Micro-skiving has been developed allowing users to have access to the skiving technique for machining inner
micro-teeth. The basic principle is similar to standard modules, with higher requirements in terms of shape, burr
and surface finish. Modules as low as 0.15 have already been produced and the technical limits to go even lower
are regularly crossed.
These developments expand the possibilities for fast and high-volume production of parts with internal micro-
teeth. The production of micro-subassemblies, medical micropumps or micro-reducers can now be considered
without the current manufacturing challenges of cycle time and quality level.
That being said, micro-skiving internal gear cutting requires suitable, high accuracy machines with fine adjustment
options. In addition, a perfect synchronization between the spindles of the part and the tool is necessary. Once all
these parameters mastered, machining times and therefore productivity are matchless.
ISBN: 978-1-64353-058-1
19FTM20. Rapid and Precise Manufacturing of Special Involute Gears for Prototype Testing
Author: Christian Weber, Thomas Tobie, and Karsten Stahl
Due to the steadily increasing demands on the power density of mechanical transmissions, gears with special
geometries are increasingly coming into focus and therefore the need for short-term availability of prototypes.
Such special gear designs are e.g. asymmetrical gears with different normal pressure angles on the drive and
coast flank. These are particularly suitable for use in gearboxes with preferred driving direction, whereby the
loaded flank can be optimized with regard to load carrying capacity. While for symmetrical gears with normal
pressure angles in the range of αn = 20° standardized calculation methods for gear design have been available
for decades, mainly theoretical numerical investigations have been carried out on asymmetrical gears so far. For
the qualification of any such designed asymmetrical gear geometry with increased load carrying capacity potential
for use in industrial practice, however, reliable load carrying capacity values are required. Therefore, according to
the current state of the art, prototype tests are indispensable to determine the actual gear strength. At the Gear
Research Centre (FZG), such load capacity investigations are carried out using back-to-back test rigs and
pulsator test rigs. The design and procurement of special tools for the production of such prototype gears is often
time-consuming and expensive. In this paper, an alternative method for a fast and cost-efficient production of
asymmetric gears for prototype tests is presented. The focus is on the grinding process from a full blank test
specimen. This process was applied at the FZG in cooperation with Liebherr-Verzahntechnik GmbH in order to
produce asymmetrical test gears for experimental investigations of the tooth root bending strength. Very good
results were achieved with regard to gear quality and shape accuracy, especially in the tooth root area, which is
then investigated. The results of this paper show therefore a suitable method for the fast, precise and cost-
efficient production of special gears for prototype tests.
ISBN: 978-1-64353-059-8
19FTM21. A Comparison of Surface Roughness Measurement Methods for Gear Tooth Working Surfaces
Author: Matthew Wagner, Aaron Isaacson, Mark Michaud, and Matt Bell
Surface roughness is a critical parameter for gears operating under a variety of conditions. It directly influences
friction and contact temperature, and therefore has an impact on various failure modes such as macropitting,
micropitting and scuffing. Typically, gear tooth surface roughness is measured using a stylus profilometer, which
yields a two dimensional cross section of the surface from which roughness parameters are taken.
Stylus profilometry can produce inconsistent results if measurements are not executed correctly. Variables such
as measurement parameters, stylus tip radius, and repeatability of stylus orientation relative to the gear tooth can

all impact measurement results. This paper examines measurements from one “shop floor” and one “metrology
lab” profilometer, both using two different stylus tip radii on the same gear teeth. Measurements from ground, shot
peened and superfinished surfaces are compared.
Although stylus profilometry is convenient, a limited amount of information regarding the surface topography of the
tooth is retained. Tooth replicas subsequently evaluated with optical interferometry offer an alternative means to
measure surface roughness, and allow for retention of a much more complete representation of the tooth surface
for future evaluation. The three dimensional surface profile generated by optical interferometry can also highlight
features that would be difficult to evaluate using stylus profilometry. This paper compares roughness
measurements made using optical interferometry of gear teeth with optical interferometry of tooth replicas. Two
different replication techniques are evaluated. The same teeth measured using stylus profilometry are used, thus
the interferometry results are directly compared to the profilometry measurements. Lastly, when tooth replicas are
taken and measured with optical interferometry, the reference frame of the gear from which the replica is taken is
not immediately apparent. A method for correlating tooth replica coordinates to roll angle is also presented, which
is shown to be useful for plotting roughness trends at points of interest over the active profile of the tooth.
ISBN: 978-1-64353-060-4
19FTM22. Influence of the Load-Dependent Shift of the Center Distance of Cylindrical Gears on the
Calculated Load Capacity and Noise Excitation Using an Analytical Mesh Stiffness Approach
Author: Stoyan Radev
The nominal center distance in cylindrical gears is defined for the non-loaded state. The center distance changes
under load conditions, which leads to a reduction of the plane of contact and respectively of the length of the
effective path of contact. The effective total contact ratio is also shortened. This affects the load and pressure
distribution on the flank and thus the load capacity of the gears. The transmission error is also mutated, which
affects the noise excitation of the gear pair.
For the analysis of these effects, we are using an analytical approach for the calculation of the local mesh
stiffness. It is based on the Schmidt plate theory and the local gear tooth deformation approach according to
Weber-Banaschek. We are evaluating the load capacity using the calculated pressure distribution on the flanks
based on the static deformation analysis of the gear system. Shafts are modelled analytically as Timoshenko
beams and bearings are considered as non-linear elements depending on the internal contact situation. In
addition, the tooth root stresses are taken into consideration using a boundary element method (BEM). The noise
excitation is evaluated using transmission error, force excitation, and other resulting characteristic values. These
are formed using a Fourier transformation and level formation. This analytical approach allows excellent
calculating precision while achieving high calculation performance. This paper shows the importance of
considering the load-dependent change of the center distance for the calculation and layout of cylindrical gears.
Furthermore, we show the advantages of using an analytical approach for calculating mesh stiffness.
ISBN: 978-1-64353-061-1
19FTM23. New Standardized Calculation Method of the Tooth Flank Fracture Load Capacity of Bevel and
Hypoid Gears
Author: Josef Pellkofer, Michael Hein, Karsten Stahl, Tobias Reimann, and Ivan Boiadjiev
Bevel and hypoid gears are widespread in automotive, industrial, marine and aeronautical applications for
transmitting power between crossed axles. Future trends show that the demands on bevel and hypoid gears for
higher power transmission and lower weight are continuously increasing. A major aspect in the design process is
therefore the load carrying capacity regarding different failure modes. Beside typical fatigue failures like pitting and
tooth root breakage, which are the results of cracks initiated at or just below the surface, there are also failures
caused by cracks starting in greater material depth in the area of the active flank that can be observed on bevel
and hypoid gears. These cracks typically propagate to the tooth root area of the unloaded flank and to the surface
of the active flank. The failure mode known as tooth flank fracture occurs particularly frequently on large spiral
bevel and hypoid gears because this gear type shows larger equivalent radii of curvature compared to spur and
helical gears. As a result of the larger equivalent radius of curvature the maximum shear stress occurs in a larger
material depth, where the material of a case hardened gear shows a decreased strength. Important parameters
influencing the tooth flank fracture load capacity are geometry, operating conditions, material and heat treatment
of the gear set. Tooth flank fracture usually leads to the total breakdown of the gearbox and generally occurs
suddenly and unexpected since the crack initiation and propagation takes place below the tooth surface and
therefore cannot be identified within visual inspections.
This paper will give an overview of the subsurface failure mode known as tooth flank fracture on bevel and hypoid
gears. Further a newly developed standardized calculation method for determining the tooth flank fracture load
capacity based on the geometry of virtual cylindrical gear according to the standard ISO 10300 (2014) will be
explained in detail.
ISBN: 978-1-64353-062-8

19FTM24. Calculated Scuffing Risk: correlating AGMA 925-A03, AGMA 6011-J14 and Original MAAG Gear
Predictions
Author: John Amendola, Sr., John Amendola III, and Robert Errichello
Predicting scuffing risk is a critical factor when designing high speed gears. In years past, scuffing risk was not
calculated for gear tooth ratings for through hardened gears. Now, case hardened gears allow higher tooth loads
making it necessary to calculate scuffing risk. AGMA and ISO application standards rate only macropitting and
bending fatigue resistance. Both AGMA and ISO provide information sheets and technical specification reports,
but neither provides a specific design standard for assessing scuffing risk.
Scuffing is severe adhesive wear occurring on gear tooth flanks when oil film thickness is insufficient to prevent
transfer of metal from one gear tooth surface to the mating gear tooth due to welding and tearing. It usually occurs
during startup of new gears thereby requiring design modification, load adjustment, or lubricant change.
Nevertheless, it can occur after years of service if the oil deteriorates or load distribution across gear tooth flanks
changes.
This paper compares three methods for calculating scuffing risk using performance data for real gears and
presents a simplified method that assures accurate prediction of scuffing risk.
ISBN: 978-1-64353-063-5
19FTM25. Optimum Carburized and Hardened Case Depth

Author: Robert Errichello, and Andrew Milburn
The optimum carburized and hardened case depth for each gear failure mode is different and must be defined at
different locations on the gear tooth. Current gear rating standards do not fully explain the different failure modes
and do not clearly define the different locations that must be considered. Furthermore, they use different hardness
values to define effective case depth and provide different values for recommended case depth. This paper
explains why case hardening is beneficial; the risks involved and compares the methods for calculating and
specifying case depth per the ISO 6336-5 and ANSI/AGMA 2101-D04 gear rating standards, and guidelines
presented in the MAAG Gear Handbook. The paper shows the three locations that the case depth needs to be
specified and presents separate calculation methods to determine the optimum case depth to avoid the failure
modes of macropitting, subcase fatigue, bending fatigue, and case/core separation. For each failure mode there is
a minimum case depth below which the load capacity drops off. On the other hand, an excessively deep case
decreases load capacity, increases cost, and has other detrimental effects that are explained.
ISBN: 978-1-64353-064-2
19FTM26. Sizing of Profile Modifications for Asymmetric Gears

Author: Ulrich Kissling
Today, the benefits of asymmetric gears are being extensively discussed. They have yet to be widely adopted, but
investigations are ongoing as to whether gear reducers can be improved with such techniques. The geometric
definition of asymmetric gears is shortly described. The strength calculation of such gears can be calculated
according to ISO standards, but the method for the bending stress must be adapted. This permits the power
capacity of asymmetric gears to be calculated and compared with symmetric gears. In specific cases, when using
asymmetric gears, the power capacity of a gear pair can be increased by up to 30%.
The power capacity of a gear pair is critical, but the noise and vibration behavior is also highly relevant. With
appropriate profile modifications, gears can be significantly improved. A modification of the gear profile will change
the load distribution during a meshing cycle, therefore changing transmission errors, contact pressure and power
losses. Additionally, with tip and/or root relief, the contact shock at the beginning and the end of the meshing can
be removed, substantially reducing the vibration and noise of the gear mesh.
The layout of profile modifications must be verified by a loaded tooth contact analysis (LTCA), which permits the
analysis of the contact during a meshing cycle step by step. LTCA can be performed based on a finite element
method (FEM) or with semi-analytical method (usually based on the Weber-Banaschek approach [1]). To get an
optimum solution for a profile modification, it is very convenient to use a parameter variation technique. For
example, tip relief and tip modification length are varied to find the best solution. For such a task with some
hundreds of variants to check, the calculation time for an LTCA analysis becomes an issue, therefore, the use of
the Weber-Banaschek approach is preferred. This approach was recently adapted for asymmetric gears to allow
for efficient analysis.
The selection process of a steel gear with asymmetric teeth is discussed in detail. With a well selected profile
modification, the noise excitation and Hertzian pressure can be reduced. The behavior of the critical parameters
was verified for different torque levels and for helix and profile errors due to manufacturing tolerances.
ISBN: 978-1-64353-065-9

2018 PAPERS
18FTM01. Filling Some Gaps in Spline Design Guidelines: Centering, Friction, and Misalignment
Author: Stephen McKenny
International spline standards and other widely used published documents have detailed definitions of two-
dimensional spline geometry, and while they cover basic axial effects and stresses, more can be provided for
design engineers. Results from an analytical study of misalignment factors and an experimental study of centering
forces are discussed to provide information to help refine calculation methods. These include: how to calculate the
effective pressure angle of straight-sided splines that must be used to accurately determine normal and radial
loads; how to calculate the effective centering force of a spline pair; how to calculate the centering moment of a
spline with ‘topping’; an update to current publications; and an update to the calculation of the maximum axial
force that a spline can transmit via friction.
ISBN: 978-1-64353-004-8 Pages: 15
18FTM02. Methods to Determine Form Diameter on Hobbed External Involute Gears

Author: Shuo Zhang
Two mathematical methods have been developed to be used for the calculation of true involute form diameter
when specialized software or original gear designer information is not easily accessible. These methods are
designed for external involute gears produced by the hobbing process, possibly followed by a finishing operation.
Method A is a more precise match, but it requires special inputs that may be time consuming without special
software. Method B, although not as accurate, still has relative error of TIF diameter below 0.1% over wide ranges
of gear design parameters. Method B is also easy to apply and can be integrated into most existing gear design
programs.
ISBN: 978-1-64353-005-5 Pages: 16
18FTM03. Optimization of a Rack and Pinion Design for Offshore Jack-Up Applications
Author: Adrian Nowoisky
Lift boats or Jack up oil rigs are essential for the oil and gas industry. One offshore jacking system is pinion and
rack to elevate legs and hull in operation. It is well known that rack and pinion of such applications exceed the
permissible contact stress by the factor of 2 to 5. The design and evaluation of such systems is still a technical
challenge. The pinion will be typically highly modified and analyzed based on the Hertzian contact stress theory of
two cylinders in contact. This method will show how to start with a basic rack and pinion design. The true involute
profile of the pinion will be replaced with a multi radii profile. In a second step, the pinion design will be analytical
optimized to reduce the contact stress and improve the life expectation. The influence of major gear parameter
such as module, profile shift coefficient as well as the pressure angle will be analyzed and explained. The results
of the final pinion will be compared with an existing pinion design to evaluate and discuss a reuse of existing
hardware. The results of the final designs will be verified by a numerical method. This paper demonstrates the
impact of major gear parameters for a pinion design and their impact on the life expectation. The benefit of a
custom pinion design and how much improvement can be achieved with emphasizing the design process properly
will be shown. Furthermore it shall serve as a guideline for best practice to design a rack and pinion for offshore
jacking applications.
ISBN: 978-1-64353-006-2 Pages: 13
18FTM04. Gearbox Development for the Food and Beverage Processing Industry
Author: Sandeep V. Thube
Industry-specific power transmission needs can be efficiently served by a streamlined product development
process. The ‘Food and Beverage’ industry has a variety of gearbox applications which are regulated by
governmental industry standards, such as NSF and FDA. The scope of this paper is to design and construct a
gearbox in compliance with these standards, which may be substantially different from typical industrial
requirements.
The paper discusses details of a gearbox development for food and beverage applications. It mainly includes
stainless steel housing and shaft designs, as well as oil seal, bearing and lubricant selections. The development
process utilizes tools, viz. Quality Function Deployment (QFD), Failure Mode Evaluation Analysis (FMEA),
computational ‘Finite Element Analysis’ (FEA), and 3D printing followed by prototype testing. QFD is used to
prioritize features to be included in the product. Potential failures of the gearbox are identified with FMEA. The
structural and thermal optimization of the newly designed housing is performed using FEA. 3D printing is utilized
to find design defect at early stage, and validate the gearbox assembly procedure. Minimizing the number of
physical prototype testing and iterations is the primary objective for the utilization of these tools.
ISBN: 978-1-64353-007-9 Pages: 20

18FTM05. Increasing Static Friction with Laser
Author: Gerhard Flores
Flat and curved surfaces with the functionality of high static friction are increasingly needed for force-fitted nonslip
power transmissions. This is especially true for con rod and cam structuring for high torque resistance or front
face connections of sprockets, gears, or cam shaft adjustments. Expensive solutions such as diamond layers,
diamond coatings, or form fitting design are increasingly being substituted. A modified laser process with defined
exposed micro structures is the alternative for innovative manufacturing. Exposed micro melting burrs of smaller
micrometer height with martensitic material structures are the precondition for the required high friction. So, such
high static friction surfaces can be produced economically with repeatability of small tolerances in high-volume
productions.
ISBN: 978-1-64353-008-6 Pages: 10
18FTM06. Design and Optimization of a Hybrid Vehicle Transmission

Author: Massimiliano Turci
Hybrid vehicles seem to be the fastest solution for the containment of consumption and of pollution for personal
transport. The designer of a hybrid transmission has to address additional issues with respect to the classical
cases, in particular the high speed of the electric unit and the bidirectional motor/generator operation. In this case,
a lot of attention should be paid to how to consider the four combinations of signs for torque and speed in the load
spectrum. This paper discusses several approaches for the alternating bending factor, the effects of the
asymmetric crowning (especially the helix modification tapered or parallel) and how to consider the housing
stiffness in the TCA. Also included is an interesting solution from the kinematic point of view, the compound
planetary, relatively well-known in the automotive, but much less so in industrial gearbox design.
ISBN: 978-1-64353-009-3 Pages: 17
18FTM07. Influence of Thermal Distortion on Spur Gear Tooth Contact

Authors: Jon Larrañaga, Ibai Ulacia, Aurea Iñurritegi, Aitor Arana, Jon German, and Julen Elizegi
The reduction of component size and oil volume of current automotive and aeronautical transmissions, along with
the increasing input speeds, are pushing gear teeth bulk temperatures to their scuffing limit. Even with
development of new lubricant additives and coatings, high temperatures may produce other issues. This paper
analyzes the effects of thermal distortion on the profile geometry and tooth contact parameters in the transverse
plane of a spur gear by calculating the steady-state temperature distribution relevant to immersion depth, sump
temperature, and lubrication regime in the contact area. Then, thermally distorted geometry and tooth contact
analysis is computed by means of a 2D finite element model where load distribution, transmission error, backlash,
and other parameters will be analyzed. The results of the study will allow one to set the limits of design backlash
to avoid gear jamming and to size the initial profile shift or tooth modifications to reach the desired contact
behavior.
ISBN: 978-1-64353-010-9 Pages: 13
18FTM08. Oil-Off Characterization Method Using In-Situ Friction Measurement for Gears Operating Under
Loss-of-Lubrication Conditions
Authors: Aaron C. Isaacson and Matthew E. Wagner
The oil-off performance evaluation of gears is of significant interest to the Department of Defense and various
rotorcraft manufacturers, so that the aircraft can safely land in an accidental loss-of-lubricant situation. However,
unlike typical gear failure modes, gear failure in an oil-off situation is very rapid and likely catastrophic. This paper
describes the procedure and instrumentation utilized for an oil-off test to measure the frictional loss in the test
gear mesh and the “air” temperature just out of mesh. Sound and vibration data was also recorded during testing.
Data from typical failures showing the detection of scuffing onset and its progression to catastrophic failure for
gears made from several aerospace alloy steels is presented.
ISBN: 978-1-64353-011-6 Pages: 17
18FTM09. Application of Finite Element Analysis for the Strain Wave Gear Tooth Surfaces Design and
Modifications
Authors: Zhiyuan Yu and Kwun-Lon Ting
This paper is on a rigorous definition and parametric study of tooth surface modification of the strain wave gear.
You will see that optimal modification for a sample strain wave gear is found from FEA and tested by contact
pattern, transmission error, and life cycling experiments. The resulting innovative design with modified fully
conjugate tooth surface improves accuracy, backlash, and the life of the existing design.
ISBN: 978-1-64353-012-3 Pages: 15

18FTM10. Experimental Study on the Pitting Detection Capabilities for Spur Gears Using Acoustic Emission
and Vibration Analysis Methods
Authors: Mateusz Grzeszkowski, C. Gühmann, P. Scholzen, Christoph Löpenhaus, S. Nowoisky, and G.
Kappmeyer
This paper discusses an experimental investigation on spur gears to characterize the pitting degradation process
using monitoring features. Previous investigations have revealed that pitting has an impact on the gear vibration
behavior. But is it possible to detect pitting at an early stage using acceleration sensors and acoustic emissions
(AE) sensors to avoid consequential damages and subsequent correction activities? The paper will discuss this
experimental investigation on spur gears to characterize the pitting degradation process using monitoring
features. Also included is a discussion of the results of the investigation, including how the results show that a
detection of pitting is possible several hours before complete gear failure, and more.
ISBN: 978-1-64353-013-0 Pages: 17
18FTM11. Optimization of Power Density by Local Gear Failure Modeling

Authors: Marco Kampka, Christian Brecher, Christoph Löpenhaus
Power density is a key factor in gear design. Increasing the power density enables engineers to use smaller gears
for their applications, which leads to smaller and lighter gear boxes. The most common way to design gears is
using industry standards in which material strength can be obtained either from fatigue limit tables or by means of
empirical formulae. Due to limited empirical data, a lot of averaging and approximations are used to make the
available standards applicable to a wide range of applications. To design the gear closer to the power density
limit, a high level of information is necessary. The paper shows how local FEA-based calculation approaches can
be used to design gears closer to their power density limits for pitting, tooth root breakage, and flank fracture. The
calculation results will be validated in running tests on different test rigs.
ISBN: 978-1-64353-014-7 Pages: 21
18FTM12. Load Intensity Distribution Factor Evaluation from Strain Gauges at the Gear Root
Authors: José Calvo Irisarri, Unai Gutierrez Santiago, Alfredo Fernández Sisón, and Pedro Olalde Arce
Strain gauges are commonly used to obtain the load intensity distribution on the flank of a gear mesh. To get the
load distribution on the flank, the strain data must be processed and changed into load intensity distribution on the
tooth flank. Research has been conducted on the best methodology to place strain gauges when calculating load
intensity distribution on the flanks of a gear. This paper discusses these research methods that use FEM models
and his analysis of how to deal with the effect of strain gauge positioning errors, in order to find the optimal
placement.
ISBN: 978-1-64353-015-4 Pages: 18
18FTM13. Impact of Root Geometry Manufacturing Deviations from a Theoretical Hob Rack on Gear Bending
Stress
Authors: Rahul V. Nigade and Carlos H. Wink
Gear reliability is a key requirement of any automotive transmission. Two common failure modes of gears are
pitting and bending fatigue. So, the total gearing reliability depends upon the bending and pitting reliability. This
paper discusses a comparison of a theoretical root fillet geometry generated by the hob racks of gear drawings to
an actual measured tooth fillet geometry of manufactured gears, which determines the impact of the different root
fillet geometries on tooth bending stresses. An emphasis is placed on the importance of using a root fillet
geometry truly representative of the actual gears in production for the bending stress calculation so that the
required bending reliability can be achieved in the field.
ISBN: 978-1-64353-016-1 Pages: 9
18FTM14. Fatigue Life Predictions of Spherical Gear Couplings

Authors: Ibai Ulacia, Jon Larrañaga, Aitor Arana, Aurea Iñurritegi, and Julen Elizegi
Spherical gear couplings are mechanical components that allow transmitting torque by means of equally spaced
teeth. Modern roll-leveling machines are characterized to level high-strength steels by using small rolls under high
torque requirements. The small size of the rolls decreases the space between the spline couplings, causing
misalignments up to 7 degrees. This paper discusses a geometry-generating procedure that has been developed
for both the hub with internal teeth and the crowned teeth shaft in spherical gear couplings. A finite element model
has been developed to study the effect of backlash and misalignment on the number of teeth in contact and root
stresses. Finally, fatigue tests are performed, and numerical predictions are correlated with experimental results.
ISBN: 978-1-64353-017-8 Pages: 12

18FTM15. Potentials of Free Root Fillets in Planetary Gearbox Applications
Authors: Jonas Pollaschek, Christian Brecher, Christoph Löpenhaus
Planetary gear stages are commonly used in many different fields of application, including wind turbine and
automotive gearboxes. This paper discusses the potential for increased root load carrying capacity at the planet
gear of a planetary gear application. The approach considers local material characteristics such as hardness,
fatigue strength, and mean stress sensitivity, as well as residual stresses and different stress rations that result
from the mesh with the sun and ring gear. It offers a detailed tooth contact analysis based on the Finite Element
Method. The result of this work allows for the possibility of changes in the gear design.
ISBN: 978-1-64353-018-5 Pages: 17
18FTM16. Microgear Measurement Standards: Comparing Tactile, Optical and Computed Tomography
Measurements
Authors: Stephan Jantzen, Martin Stein, Karin Kniel, and Andreas Dietzel
Microgears are widely used in industry, as they are essential components of gearboxes used in precision
engineering, medical technology, and robotics. This paper discusses the development of a new internal involute
microgear measurement standard for research and industry. A comparison between the tactile calibration
performed using a micro coordinate measuring machine (µCMM) and the measurement results obtained by
means of a computer tomography (CT) system and optical CMM will be presented. The new results, compared
with the results of the comparison measurements of the external microgear measurement standard, are
discussed. The results and discussion will provide an overview of the state of the art in microgear metrology.
ISBN: 978-1-64353-019-2 Pages: 23
18FTM17. Generative Gear Milling

Authors: Yefim Kotlyar
This paper discusses Generative Gear Milling, an innovative software feature for gear cutting. The involute
generative principle is based on an incremental positioning of a simple and inexpensive milling “disk” cutter with
trapezoidal or parallel sides on the “line of action.” The paper outlines the needs for this procedure and the
applications of generative milling. And, the author discusses the benefits of Generative Gear Milling, including
improved efficiency; reduced cutter cost and delivery time; and expanded pitch range capability.
ISBN: 978-1-64353-020-8 Pages: 19
18FTM18. Reducing Tool Wear in Spiral Bevel Gear Machining with the Finite Element Method
Authors: Fang Hou, Yantao Zhang, Syed Wasif, Pete Mattson, and Kerry Marusich
Due to the complexity of spiral bevel gear machining, the cutting tools can be a significant cost of gear
manufacturing. Unlike the price of material which is fixed by the market, the cost of tooling and subsequent re-
grinding can be reduced through reducing tool wear and increasing tool life. This paper discusses an alternative
approach to physical testing for predicting and reducing tool wear using the finite element method. This virtual
design approach utilizes real-world cutting tool geometry, automatically generated gear blanks, and known
process kinematics to simulate the cutting process. Additionally, lessons learned, potential benefits and pitfalls of
this approach to tool wear reduction and future work will be discussed.
ISBN: 978-1-64353-021-5 Pages: 13
18FTM19. Method for High Accuracy Cutting Blade Inspection

Authors: Haris Ligata and Hermann J. Stadtfeld
Inspection of the cutting blade is a crucial step in the manufacturing of bevel gears. The proper blade geometry
ensures that the desired gear tooth form can be achieved. The accuracy of the process can be compromised
when the blade consists of several small sections, or when dust particles, surface roughness, or floor vibration
during the data acquisition occurs. This paper highlights a new method for improving the robustness of the
inspection process in such cases. A proposal for using larger portions of the blades to evaluate the properties of
the small features will be shown. The paper discusses the methods developed and provide several examples of
gears made using these methods.
ISBN: 978-1-64353-022-2 Pages: 14
18FTM20. Fully Automated Roughness Measurement on Gears, Even on the Shop Floor
Author: Georg Mies, Klingelnberg
For many years, the focus of the design of precision components for transmissions has been on optimizing gear
geometry. The work in this area has come so far that we are now seeing a shift from design to a concentration on
surface quality of the functional surfaces. The roughness of highly stressed gear flanks has significant influences
on noise, wear, and power loss. Thanks to new or improved machining technologies, extremely smooth surfaces
can now be produced cost-effectively. The need now arises for reliable measurement of roughness of gears. This
paper discusses the newest solution that enables fully automatic measurements of gear geometry and roughness
in one clamping.
ISBN: 978-1-64353-023-9 Pages: 14

18FTM21. Integrating Non-Contact Metrology in the Process of Analysis and Simulation of Gear Drives
Authors: Alfonso Fuentes-Aznar and Ignacio Gonzalez-Perez
Non-contact metrology allows for a very fast collection of points on the measured gear tooth surfaces, with data
rates that can be as high as millions per second. It is a wealth of information about the gears. This paper
discusses using this data for reverse engineering, noise root cause analysis, or as a baseline for stress
information for further gear design optimization. Also presented is an approach on integration of non-contact
metrology to enhance current methodology of analysis and simulation of gear drives.
ISBN: 978-1-64353-024-6 Pages: 16
18FTM22. Integrated Approach for Gear Testing of High-Performance Clean Steels

Authors: Dieter Mevissen, Christoph Löpenhaus, Lily Kamjou, and Elias Löthman
The power density of gearboxes is continuously increased by different research activities. Besides new material
developments, the cleanliness of steels comes to the forefront in order to meet future requirements regarding load
carrying capacity of gears. This paper discusses an integrated approach for gear testing of steels. In order to
determine the differences between steels of different cleanliness levels, the testing approach has to be improved
as a whole.
ISBN: 978-1-64353-025-3 Pages: 14
18FTM23. Lean Heat Treatment for Distortion Control

Authors: Volker Heuer and David Bolton
Controlling distortion is of key importance during the case hardening process in the production of gear
components. By effective control of distortion and the variation of distortion, significant costs in post-heat
treatment machining processes can be avoided. This paper focuses on new vacuum furnace designs that allow
the treatment of small batches in a single layer of parts (2D treatment), which allows for easy automated loading
and unloading of the fixture-trays. When performing case hardening, the components are Low Pressure
Carburized (LPC) at high temperatures, followed by gas quenching. The treatment in single layers offers an
optimum quality with temperature homogeneity; quench homogeneity; and distortion control.
ISBN: 978-1-64353-026-0 Pages: 16
18FTM24. Residual Stress Measurement of Case Hardened Steel Gears

Author: David Easton
Aerospace gear components are required to demonstrate excellent load carrying and endurance characteristics.
Case hardened steels are often utilized for these parts, but often residual stresses are developed. These residual
stresses are known to have a significant effect on distortion during the heat treatment and machining processes.
This paper presents research conducted on gears manufactured from two different starting points: as-received bar
material and hot-forged billet. This paper will also discuss the results of the work and compare the two sets of spur
gears.
ISBN: 978-1-64353-027-7 Pages: 13
18FTM25. Combining Ultra-High-Strength and Toughness for Affordable Power Densification in Steel Gears
Author: E. Buddy Damm
In the last few years, improvements in clean steel technology have been coupled with development of new ultra-
high-strength, high-toughness steels. These technologies provide affordable solutions for critical, power-dense
components. This paper reviews and compares steel cleanness metrics between re-melted steels and steels that
meet AGMA grade 3 cleanness. The new steels provide yield strengths ranging from 175-210 KSI, ultimate tensile
strengths ranging from 230-250 KSI, and Charpy impact energies ranging from 35 to 50 ft.-lbs., allowing these
grades to provide longer life, more power, and/or lighter weight. The higher fatigue strength of these steels is
compared to more commonly used gear steels, and an analysis is presented that illustrates a potential for either a
30% reduction in gear set mass or a 45% increase in gear set torque capacity.
ISBN: 978-1-64353-028-4 Pages: 15
18FTM26. Reliability of Gears – Determination of Statistically Validated Material Strength Numbers

Authors: Michael Hein, Michael Geitner, Thomas Tobie, Karsten Stahl, and Burkhard Pinnekamp
This paper is intended to provide a review on the statistical reliability behavior of cylindrical gears with regard to
pitting and tooth root breakage failures. A mathematical reliability approach was developed and drafted to expand
standardized load capacity calculation methods. The deduced models and procedures allow the consideration and
conversion of different reliability levels in the design process of cylindrical gears. Practical examples of the
research are provided.
ISBN: 978-1-64353-029-1 Pages: 22

2017 PAPERS
17FTM01. CFD Simulation of Power Losses and Lubricant Flows in Gearboxes
Authors: Franco Concli, Carlo Gorla
This paper describes the application of Computational Fluid Dynamics simulation of power losses and lubricant
flows in gearboxes based on an original global re-meshing technique. This enables accurate predictions in
relatively short simulation times, compatible with the industrial design practice. The results of the practical
applications used for the validation are also included and discussed in the paper.
ISBN: 1-55589-527-3 Pages: 14
17FTM02. Understanding the Dynamic Influences of Gear Oils and Radial Shaft Seals
Authors: Matthias Adler, Joe Walker, Sascha Grasshoff, Craig Desrochers, Matthias Pfadt
Approximately 40 percent of long-term gearbox leakages can be traced back to poor interaction between the
Radial Shaft Seal (RSS) and the lubricant. This paper highlights the most critical interactions between the
industry’s most commonly used gear oil formulations, with emphasis on synthetic oils with Nitrile- and
Fluoroelastomers. Through an ideal combination of base oil and additives, the demand of life expectancy on the
radial shaft seals can be met.
ISBN: 1-55589-529-7 Pages: 15
17FTM03. Gear Tooth Strength Analysis of High Pressure Angle Cylindrical Gears
Authors: Alfonso Fuentes-Aznar, Ignacio Gonzalez-Perez
In this paper, the gear tooth strength of high pressure angle gears is studied and compared with that of
conventional pressure angle gears. The comparison will be performed regarding contact pressure, contact and
bending stresses, loaded function of transmission errors, and comparison of errors of alignment and shift of
contact pattern when mounted in similar shafts.
ISBN: 1-55589-537-2 Pages: 18
17FTM04. The Effectiveness of Shrouding on Reducing Meshed Spur Gear Power Loss – Test Results
Authors: Irebert R. Delgado, M. J. Hurrell
Reducing power losses to rotorcraft gearboxes, due to windage drag and viscous effects on rotating, meshed gear
components would allow gains in areas such as vehicle payload, range, mission type, and fuel consumption. One
method used in rotorcraft gearbox design attempts to reduce losses is to use close clearance walls to enclose the
gears in both the axial and radial directions. This paper examines using meshed spur gears at four shroud
configurations and compares the data to available data.
ISBN: 1-55589-547-1 Pages: 15
17FTM05. Complete Measurement of Gearbox Components

Authors: Christof Gorgels
In today’s production environment, a variety of different measurement devices, such as CMMs, gear checkers,
form testers, and roughness testers, are used to assess the quality and accuracy of workpieces, many of which
require specialized training and environments. This paper describes how a Circular CMM (CCMM) can be
integrated into a production environment. The benefits and challenges of the use of a CCMM will be discussed.
ISBN: 1-55589-567-9 Pages: 11
17FTM06. The Effect of Asymmetric Cutter Tip Radii on Gear Tooth Root Bending Stress
Authors: Abdullah Akpolat, Nihat Yildirim, Burak Sahin, Omer Yildirim, Bulent Karatas, Fatih Erdogan
The tooth root fillet is where the maximum bending stress concentration region is located during torque
transmission via gear pairs. An increase in gear root fillet radius provides a smooth transition from involute to
trochoid, increases root critical section thickness, and the moment of inertia against bending of tooth. A 10-11%
reduction in bending stress is obtained by using asymmetric cutter tip radii coefficients for two sides of the gear
tooth profile with standard center distance and no tooth interference.
ISBN: 1-55589-568-6 Pages: 20
17FTM07. Magnetic Barkhausen Noise as an Alternative to Nital Etch for the Detection of Grind Temper
on Gears
Authors: James Thomas, Stephen Kendrish
Magnetic Barkhausen Noise (MBN), is quantitative, repeatable, and non-destructive. Further, the MBN method is
easily automated thus removing operator influence, as seen with Nital Etch, as a variable. Using a sample set of
carburized spur gears ground to varying conditions of grinding burn, the MBN method is demonstrated to match or
exceed the detection effectiveness of traditional Nital Etch. Residual stress depth distributions measured with x-
ray diffraction and electrochemical layer removal are utilized as a quantitative verification method.
ISBN: 1-55589-570-9 Pages: 11

17FTM08. Areal Evaluation of Involute Gear Flanks with Three-Dimensional Surface Data
Authors: Yue Peng, Kang Ni, Gert Goch
This paper presents the benefits of areal evaluation of gear flanks, mathematical approaches for areal description
of involute surface, deviations and modifications, and the characterization of areal data with “3D gear deviation
parameters”. Approximation and orthogonal polynomial decomposition methods are applied for surface
reconstruction and parameter calculation. Both simulated and measured gear data are analyzed, and
comparisons with conventional evaluation results are presented.
ISBN: 1-55589-578-5 Pages: 15
17FTM09. Standard Samples for Grinder Burn Etch Testing

Authors: Jonathan R. Crow, Michael A. Pershing
This paper discusses a unique method for producing a standard sample of an acid etch system that has a
consistent amount of thermal damage. Multiple degrees of burn are applied to the sample to ensure that the etch
inspection can detect all levels of potential burn on the piece parts. The sample can then be reliably used to test
an acid etch system and its method to ensure the proper amount of contrast for threshold levels of thermal
damage.
ISBN: 1-55589-580-8 Pages: 8
17FTM10. Psychoacoustic Methodology for the Noise Reduction of Bevel Gears

Authors: Hermann J. Stadtfeld
A rather exciting conclusion from the psychoacoustic research is the proposal of a gear transmission graph which
is a hybrid that connects different mathematical functions within the one pitch long contact area and the outside of
this area. The results show that the hybrid transmission function dramatically changes the way bevel and hypoid
gearsets will be optimized in the future for silent operation.
ISBN: 1-55589-613-3 Pages: 19
17FTM11. FE-Based Method for Design of Robust Tooth Flank Modifications for Cylindrical and Planetary
Gear Stages Regarding Manufacturing Tolerances
Authors: Christian Brecher, Christoph Löpenhaus, Julian Theling, Marius Schroers, Daniel Piel
The authors present a method to evaluate the quality and stability of flank modifications regarding manufacturing
tolerances during the design process, using an FE-based tooth contact analysis. The presented design process
provides a method to examine and simulate characteristics of the excitation behavior and durability of a gear pair.
This enables the engineer to choose the most robust micro-geometry in terms of quality and stability already in the
design process.
ISBN: 1-55589-616-4 Pages: 17
17FTM12. Reliability, Lifetime and Safety Factors

Authors: Stefan Beermann
This paper uses several examples to show the practical differences in using safety factors versus reliabilities. The
failure probability of all components for a specific lifetime is calculated to provide the reliability of the whole
gearbox as a system of components. This provides the engineer an easier method to compare designs and
identify the critical components.
ISBN: 1-55589-618-8 Pages: 17
17FTM13. A Comparison of Current AGMA, ISO and API Gear Rating Methods
Authors: John M. Rinaldo
There are many different gear rating methods in use today, and they can give substantially different results for any
given gear set. This paper will make it easy to understand the choices and the impact the choices have on
gearbox design. The eight standards examined are AGMA 2001, AGMA 6011, AGMA 6013, ISO 6336, API 613,
API 617, API 672, and API 677. This paper will provide a useful aid to customers who are unsure of the
differences between the standards.
ISBN: 1-55589-627-0 Pages: 45
17FTM14. Prediction of Dynamic Factors for Helical Gears in a High-Speed Multi-Body Gearbox System
Authors: Niranjan Raghuraman, Chad Glinsky, Sharad Jain
This paper will analyze the influence of operating speed, torque, system dynamics, and gear micro-geometry on
the dynamic factors of a high-speed gearbox. It will show that the dependence of dynamic factor on torque is
significant and must not be ignored, and that the presence of system resonance modes increases dynamic
factors. The dynamic factors calculated in this study are compared with the dynamic factor values suggested by
ISO and AGMA standards.
ISBN: 1-55589-628-7 Pages: 21

17FTM15. Fatigue Performance and Cleanliness of Carburizing Steels for Gears
Authors: Joakim Fagerlund, Lily Kamjou
The cleanliness of steels used for gears is of great importance when looking to improve life of gears or increase
loads. In this paper, carburizing steels with the same basic chemical composition, but with a varying cleanliness
level, are compared. The investigation showed a good qualitative correlation between the fatigue performance
and the inclusion assessment made by ultrasonic evaluation and SEM. The results also show that traditional
micro-inclusion rating methods are not sensitive enough to give a good indication of material performance.
ISBN: 1-55589-664-5 Pages: 16
17FTM16. Predicting Life on Through Hardened Steel Rack and Pinion for Jacking Applications in the
Offshore Industry
Authors: Adrian Nowoisky
It is well known in the industry that, according to AGMA and ISO gear calculation methods, the contact stresses in
rack and pinion systems for jack up applications exceed the permissible limits by a factor of 3 to 6. However,
these applications have been in service without any failures for more than 20 years. This paper will outline the
process of the analytical evaluation of a specific design and validate it with systems currently in service.
*ISBN (former): 1-55589-736-9* Pages: 14
ISBN (new): 978-1-61481-400-9
*Please note that due to a technical error, this ISBN has changed. Please disregard the previous number.
17FTM17. Four Ways Polyketone Polymers Can Improve Gear Performance

Authors: Tim Morefield
Historically, the most commonly specified resins for plastic gears have been acetal (POM), nylon (PA 66) and
polyester (PBT), with or without modifiers (PTFE, carbon fiber, glass fiber, silicone or combinations thereof) to
reduce friction and wear. Polyketone offers engineers four distinct advantages relative to other materials in
meeting design challenges: 1) superior wear properties, 2) better dimensional control / stability, 3) superior creep
rupture performance, and 4) quieter operation.
ISBN: 1-55589-737-6 Pages: 10
17FTM18. Effect of Non-metallic Inclusions on Bending Fatigue Performance in High Strength 4140 Steel
Authors: Michael Burnett
This paper studies the fatigue performance of three sets of quench and tempered 4140 steel samples,
representing three distinctly different inclusion populations. The inclusion populations for each of the sample sets
were characterized using both an SEM-based image analysis system, primarily for the micro-inclusions, and a
high-resolution UT system for the macro-inclusions. The sample sets were also evaluated using both longitudinal
and transverse specimens in all the bending fatigue tests. The results of these tests will be presented.
ISBN: 1-55589-759-8 Pages: 23
17FTM19. Sensitivity Study of Press Quench Process and Concept of Tooling Design for Reduced Distortion
by Modeling
Authors: Zhichao (Charlie) Li, B. Lynn Ferguson
The press quench process includes parameters such as heating rate, austenitization temperature, applied load
type, load amount, load locations from the tooling, friction between the tooling and the gear, and the quench rate.
All these factors can lead to inconsistent distortion, especially for the radial size of thin-wall gears. In this paper,
the effects of several critical factors on the dimensional inconsistency and tooling design are analyzed by heat
treatment modeling software.
ISBN: 1-55589-760-4 Pages: 17
17FTM20. Influences of the Residual Stress Condition on the Load Carrying Capacity of Case
Hardened Gears
Authors: Christian Güntner, Thomas Tobie, Karsten Stahl
Compressive residual stresses, such as those generated by shot peening, result in an increased tooth root
bending strength. The author’s investigations show that shot peening can increase the load carrying capacity of
case hardened gears significantly. Correlations between the residual stress state and the load carrying capacity
limits were determined. This paper will give an overview of the main results of different investigations and discuss
influences of the residual stress condition on different failure modes of case hardened gears.
ISBN: 1-55589-761-1 Pages: 18

17FTM21. Calculation of Tooth Flank Fracture Load Capacity – Practical Applicability and Main Influence
Parameters
Authors: Michael Hein, Thomas Tobie, Karsten Stahl
Due to improved material qualities, new surface finishing methods, and increased heat treatment process
reliability, flank surface damages, such as pitting or micropitting, can increasingly be prevented in a reliable
manner. At the same time, this may result in an increase of unexpected flank damages such as tooth flank
fracture. A computer-aided calculation of the risk of tooth flank fracture damages will be presented.
ISBN: 1-55589-762-8 Pages: 22
17FTM22. Full Contact Analysis Versus Standard Load Capacity Calculation for Cylindrical Gears
Authors: Michael Otto, Uwe Weinberger, Karsten Stahl
In this paper, local tooth contact analysis and standard calculation are used to determine the load capacity for the
failure modes pitting, tooth root breakage, micropitting and tooth flank breakage. Analogies and differences
between both the local and the standard approaches are shown. The example presented demonstrates a valid
possibility to optimize the gear design by using local tooth contact analysis while satisfying the requirement of
documenting the load carrying capacity by standard calculations.
ISBN: 1-55589-763-5 Pages: 14
17FTM23. The Influence of a Grinding Notch on the Gear Bending Strength Rating
Authors: Ulrich Kissling, Ioannis Zotos
To achieve the requested quality, most gears today are ground. If the gear is premanufactured with a tool without
protuberance, then at the position where the grinding tool retracts from the flank, a grinding notch in the tooth root
area is produced. A review of the formulas to calculate the effects of the grinding notch is necessary. A 3D-FEM
analysis that was used to deduce an improved formula will be presented.
ISBN: 1-55589-764-2 Pages: 19
2016 PAPERS
16FTM01. Efficient Hard Finishing of Asymmetric Tooth Profiles and Topological Modifications
by Generating Grinding
Authors: Andreas Mehr & Scott Yoders
New possibilities of modifications with the continuous generating grinding method will be presented, such as
Deviation Free Topological grinding (DFT), Generated End Relief (GER), Noise Excitation Optimized modification
(NEO), and hard finishing of asymmetric gears. The focus is on the explanation of the technical challenges, their
solutions, and the principle function of the dressing and grinding processes.
ISBN: 1-55589-060-5 Pages: 13
16FTM02. The Whirling Process in a Company that Produces Worm Gear Drives
Authors: Dr. Massimiliano Turci, Dr. Giampaolo Giacomozzi
This paper looks at the benefits that can be realized with the introduction a whirling machine into the wormgear
manufacturing facility. The benefits include time and cost savings, especially in regard to the need for grinding,
increased quality, and environmental considerations due to not needing cutting oils.
ISBN: 1-55589-061-2 Pages: 22
16FTM03. Worm Screw High-Speed Manufacturing

Author: Jean-Laurent Feutren
The conventional set-up of on a gear hobbing machine for the production of helical gears has the hob axis
perpendicular (±30°) to the workpiece. This set-up does not allow for conventional manufacturing of wormgears.
To solve this problem, a high speed method will be presented that reverses the axis between the workpiece and
tool, and utilizes a high speed spindle (up to 16 000 rpm). This method can produce wormgears eight times faster
than conventional methods.
ISBN: 1-55589-063-6 Pages: 15
16FTM04. Twist Control Grinding (TCG)

Author: Walter Graf
This paper introduces the latest process developments for the hard-finishing of gears in regards to controlling
flank twist. Flank twist occurs as a matter of course when machining helical gears that feature lead modifications,
and is brought about by the geometries and kinematics inherent in the continuous generating grinding of helical
gears. Controlling the flank twist on gears, using twist control grinding (TCG), can either eliminate twist
completely, or introduce a counter-twist to counteract the deformation of gears under load.
ISBN: 1-55589-064-3 Pages: 13

16FTM05. Review of Microstructure and Properties of Non-Ferrous Alloys for Worm Gear Application and
Advantages of Centrifugally Cast Gears
Authors: Giri Rajendran & Jason Hassen
This paper reviews the microstructure and properties of tin bronze, manganese bronze, and aluminum bronze
material that make them suitable for specific wormgear applications. The advantages of centrifugally cast bi-metal
gear blanks, and some common causes of worm gear failures are discussed.
ISBN: 1-55589-065-0 Pages: 11
16FTM06. Pre-Nitriding: A Means of Significantly Increasing Carburizing Throughput

Author: Thomas Hart
Higher carburizing temperatures allow end users to use shorter cycle times and significantly increase production
rates, but can lead to grain growth. Pre-nitriding is a relatively new technology that addresses grain growth and
allows carburizing end users to carburize at higher temperatures. Real life case studies show how carburizing
productivity has doubled, and sometimes tripled, using pre-nitriding.
ISBN: 1-55589-066-7 Pages: 10
16FTM07. Performance and Machining of Advanced Engineering Steels in Power Transmission Applications
– Continued Developments
Authors: Lily Kamjou, Nicklas Bylund, Brent Marsh, Joakim Fagerlund, Thomas Björk
This paper discusses the potential gain for the power transmissions industry by making use of the material
properties of Advanced Engineering Steels to support more demanding applications. Machining the Advanced
Engineering Steels is discussed based on a number of recent studies. All studies indicate that by optimizing
machining parameters and tools, the productivity and efficiency of these processes can be maintained, or even
improved.
ISBN: 1-55589-067-4 Pages: 16
16FTM08. Gear Design Relevant Cleanness Metrics

Authors: Dr. E. Buddy Damm, Peter Glaws
This paper describes the methods used to characterize premium quality clean steels through the use of statistics
of extreme values (SEV), and the use of these data to perform gear design relevant engineering analysis of the
potential for a gear failure due to bending fatigue in the root or flank. Literature evaluation, modeling results, and
experimental results are presented in order to validate the approach.
ISBN: 1-55589-068-1 Pages: 17
16FTM09. Development of High Hardness-Cast Gears for High-Power Applications in the Mining Industry
Author: Fabrice Wavelet
Multiple solutions are available to increase the transmissible power of girth gears, including using a larger module,
increasing the gear diameter, enlarging the face width, and increasing the hardness of the base material. Base
material hardness, the only parameter that is not limited by cutting machine size, is being increased to meet
higher power needs. This paper will review the related design and manufacturing impact of the high-hardness
gears needed to meet today’s industry demands.
ISBN: 1-55589-069-8 Pages: 14
16FTM10. Computerized Design of Straight Bevel Gears with Optimized Profiles for Forging, Molding,
or 3D Printing
Authors: Alfonso Fuentes, Ignacio Gonzalez-Perez, and Harish Pasapula
Research will be presented on whether there is a reference profile that will yeild the same advantages for bevel
gears as the involute for cylindrical gears. The spherical involute and octoidal profiles will be studied, and the
virtual generation of bevel gears with the different profiles will be developed, and simulated, using advanced tools
such as tooth contact analysis and finite element analysis.
ISBN: 1-55589-111-4 Pages: 21
16FTM11. Contact Fatigue Characterization of Through-Hardened Steel for Low-Speed Applications

Like Hoisting
Authors: Dr. Michel Octrue, Antoine Nicolle, and Remy Genevier
Lubrication by grease is often employed on open gears that transmit power at low speeds. The rating methods
found in ISO 6336 has shown that ISO is very conservative for grease lubricated, through hardened steel gears
running with case hardened pinions, specifically when considering service life. Fatigue SN curves resulting from
tests will be compared and discussed with values given in ISO and AGMA gear rating standards.
ISBN: 1-55589-112-1 Pages: 18

16FTM12. Determination of Load Distributions on Double Helical-Geared Planetary Gear Boxes
Author: Dr. Tobias Schulze
The optimization and effective utilization of planetary gearbox designs require a detailed consideration of the
loads on the gears. This paper presents a computer aided calculation method that has been developed for
planetary gearboxes with spur and helical gears that considers the most important influences on the load
distribution. Using this information, a detailed load distribution is possible to reach the maximum capability of
the gears.
ISBN: 1-55589-113-8 Pages: 14
16FTM13. Designing Very Strong Gear Teeth by Means of High Pressure Angles
Author: Richard Miller
This paper will show a method of designing and specifying gear teeth with much higher bending and surface
contact strength than that of conventional gear teeth. The primary means of achieving this is by specifying gear
teeth with significantly higher pressure angles. This paper will show calculation procedures, mathematical
solutions, and the theoretical background and equations to achieve this.
ISBN: 1-55589-114-5 Pages: 22
16FTM14. Impact of Surface Condition and Lubricant on Effective Gear Tooth Friction Coefficient
Authors: Aaron Isaacson, Matthew Wagner, Suren Rao, and Gary Sroka
Using a four-square, power re-circulating gear test rig with high accuracy torque transducers, losses due to
operating speed, surface roughness, and torque level, including two different lubricants, were compared, and
measurements of the effective coefficient of friction at the gear tooth flanks are provided. This paper summarizes
the results obtained.
ISBN: 1-55589-118-3 Pages: 12
16FTM15. Surface Structure Shift for Ground Bevel Gears

Author: Sebastian Strunk
A process is presented that improves the excitation behavior of a ground bevel gear set by altering the surface
structure of a generated member along the path of contact from slot to slot. This process addresses this
objectionable harmonic excitation by influencing each axis position in each line of the axis position table with small
predetermined or random amounts.
ISBN: 1-55589-119-0 Pages: 20
16FTM16. Developing an Energy-Efficient Industrial Gear Oil

Authors: Shubhamita Basu, Daniel Wilkerson, and James Vinci
This paper describes a laboratory test rig, test procedure, and results that are focused on quantifying increased
operating efficiency with various synthetic lubricant formulations. Fluid evaluations were conducted in an
industrial-scale worm gear efficiency rig. Operating under a wide range of speeds and loads, the rig produced
sharp differentiation among fluids for their impact on power loss and operating temperature.
ISBN: 1-55589-120-6 Pages: 14
16FTM17. Analysis of Excitation Behavior of a Two-Stage Gearbox Based on a Validated Simulation Model
Authors: Marius Schroers, Christian Brecher, and Christoph Löpenhaus
In order to reduce development and production costs of a gearbox, simulation models have been set up to predict
the noise and vibration behavior of a gearbox before the prototype phase. A simulation model, verified by
experimental results, is presented that is able to calculate the dynamic excitation behavior of a two-stage gearbox.
ISBN: 1-55589-121-3 Pages: 16
16FTM18. An Experimental and Analytical Comparison of the Noise Generated by Gears of Austempered
Ductile Iron (ADI) and Steel Materials
Authors: Dr. Donald Houser, Samuel Shon, Kathy Hayrynen, Justin Lefevre
Many have made claims concerning the relative noise performance of Austempered Ductile Iron (ADI) versus
steel as a gearing material. Predictions based on measured tooth topographies of the transmission error and "sum
of forces" gear noise metrics show that the iron gears should be slightly quieter than the steel gears at loads
beneath the transmission error optimization "notch" torque and slightly louder above this torque. This paper
presents results from a systematic experimental study to ascertain these differences.
ISBN: 1-55589-122-0 Pages: 25

16FTM19. Numerical Thermal 3D Model to Predict the Surface and Body Temperature of Spur and Helical
Plastic Gears
Authors: Niranjan Raghuraman, Donald Houser, and Zachary Wright
Tooth surface wear is an important failure mode in plastic gears and this primarily caused by the surface
temperature increasing to a value close to the melting point of the material. Thus, it is critical to compute the
temperature of the gear pair in an accurate fashion. This paper will focus on the prediction of gear temperature of
plastic gears using a numerical heat transfer model based on 3D finite difference method.
ISBN: 1-55589-123-7 Pages: 17
16FTM20. Influence of the Defect Size on the Tooth Root Load Carrying Capacity
Authors: Jens Brimmers, Christian Brecher, Christoph Löpenhaus, and Jannik Henser
Conventional calculation methods for the flank and tooth root load carrying capacity are well-established, but
models that consider the defect size on the tooth root strength have not yet been applied in fatigue models for
gears. This paper will introduce a method for calculating the tooth root load carrying capacity for gears while
considering the influence of the defect size on the endurance fatigue strength of the tooth root.
ISBN: 1-55589-176-3 Pages: 14
16FTM21. Influence of Contact Conditions on the Onset of Micropitting in Rolling-Sliding Contacts Pertinent
to Gear Applications
Authors: Dr. Amir Kadiric & Dr. Pawel Rycerz
Recently, increased sliding has been one of the factors suggested to be responsible for the onset of micropitting,
with the proposed underlying mechanism being the potential reduction of film thickness through increased sliding
speed. This paper attempts to shed light on the tribological conditions that may lead to the onset of micropitting in
lubricated, concentrated contacts representative of those occurring between gear teeth. In particular, the effect of
slide-roll-ratio, surface roughness and film thickness is studied.
ISBN: 1-55589-480-1 Pages: 19
16FTM22. Comparison of Tooth Interior Fatigue Fracture Load Capacity to Standardized Gear Failure Modes
Authors: Baydu Al, Paul Langlois, Rupesh Patel
This study aims to improve the existing understanding of Tooth Interior Fatigue Fracture (TIFF) load capacity and
compare calculated load capacity to the allowable loading conditions for bending and pitting fatigue failure, based
on standard calculation procedures. Possible methods that could be used to mitigate TIFF risk are presented, and
the effect of these methods on the performance with respect to the other failure modes are quantified.
ISBN: 1-55589-497-9 Pages: 19
16FTM23. A New Approach to Repair Large Industrial Gears Damaged by Surface Degradation – The
Refurbishment Using the Modification of Both the Profile Shift Coefficient and the Pressure Angle
Authors: Horacio Albertini, Carlo Gorla, Francesco Rosa
Superficial degradation of industrial gears, and a lack of approaches to repair them, have resulted in many gears
being discarded prematurely. This paper presents a computer program and method for repairing industrial gears,
enabled by the recent advances in multi-axis CNC machine centers, and gear grinding, that considers the
modification of both the profile shift coefficient and the pressure angle.
ISBN: 1-55589-234-0 Pages: 20
2015 PAPERS
15FTM01. Influence of Surface Finishing on the Load Capacity of Coated and Uncoated Spur Gears
Authors: P. Konowalczyk, C. Brecher
In order to increase the power density of tribologically stressed drive train components, different approaches are
being pursued in material and production technology. In addition to the development of efficient base materials,
especially the optimization of surface finishing processes and the application of coating systems are promising. By
combining mechanically highly stressable substrate materials and tribologically effective, extremely thin coatings,
the components show modified wear and friction properties, which often lead to an increase of tooth flank load
carrying capacity. A major advantage of this approach is that the highly accurate component geometry is only
slightly changed by the coating.
The influence of PVD/PECVD hard coatings on the load carrying capacity of cylindrical gears made of alloy steel
is the subject of scientific research since the nineties. Several reports show that diamond-like carbon (DLC)
coating systems reduce the occurrence of specific forms of gear damages, such as pitting or scuffing, and
optimize the frictional behavior of gears. Despite the good results, PVD/PECVD coating technology could not be
established in gear transmission technology yet. The use of a PVD/PECVD coating leads to higher component
costs and longer manufacturing time. Furthermore, the surface finishing process before coating can influence the
resulting tooth flank load capacity, and in some studies, a reduction of tooth root strength by the application of a

coating can be observed. An extensive research concerning the influence of specific surface finishing processes
on the tooth flank load capacity of uncoated and coated gears have not been focused in existing works.
Furthermore, the existing works focus on the coating of both gears in contact and not on the coating of just one
gear combined with optimized surface finishing processes.
Therefore, the aim of this work is the investigation and determination of the influence of surface finishing
processes on the impact of PVD/PECVD coatings concerning the pitting load capacity of gears. By means of
running tests, the influence of different surface finishing processes on the pitting resistance is examined for the
uncoated and coated tooth flank contact. The coated tooth flank contact will be further separated in the cases with
just one or two coated gears in contact. By coating only one gear, a possible reduction of coating costs with
simultaneous increase of the pitting resistance is targeted. As a DLC coating, a modified tungsten carbide coating
(a-C:H:W (WC/C)) will be applied. Due to an optimized coating process, consistent coating adhesion without loss
of hardness of the substrate material will be achieved. The result of this optimization will additionally be proven by
the investigation of tooth root strength by means of pulsator testing.
ISBN: 1-55589-006-3 Pages: 11
15FTM02. Improved Materials and Enhanced Fatigue Resistance for Gear Components
Authors: Dr. Volker Heuer, Dr. Klaus Loeser, Gunther Schmitt
This paper shows the latest progress in steel grades and in case hardening technology for gear components.
To answer the demand for fuel-efficient vehicles, modern gear boxes are built much lighter. Improving fatigue
resistance is a key factor to allow for the design of thin components to be used in advanced vehicle transmissions.
The choice of material and the applied heat treat process are of key importance to enhance the fatigue resistance
of gear components.
By applying the technology of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ), the
tooth root bending strength can be significantly enhanced, compared to traditional heat treatment with
atmospheric carburizing and oil quenching.
Besides heat treatment, significant progress has been made over the past years on the steels being used for gear
components. The hardenability of case hardening steels such as 5130H, 5120H, 20MnCr5, 27MnCr5,
18CrNiMo7-6 etc. has been stepwise increased in recent years. An important factor for fatigue resistance is the
grain size after heat treatment. Therefore, grain size control is a key goal when developing new modifications of
steel grades.
After enhancing grain size control, it was possible to increase the carburizing temperatures over the past years
from 930°C to 980°C (1700°F to 1800°F) which resulted in shorter heat treatment cycles and thus in significant
cost savings.
With the introduction of new microalloyed steels for grain size stability, carburizing temperatures can now be even
further increased to temperatures of up to 1050°C (1920°F), leading to even more economic process cycles. By
adding microelements such as Niobium or Titanium in the ppm-range, nitride and carbonitride-precipitates are
formed. These precipitates effectively limit the grain-growth during the heat treatment process.
ISBN: 1-55589-008-7 Pages: 16
15FTM03. Practical Approach to Determining Effective Case Depth of Gas Carburizing

Author: March Li
Effective case depth is an important factor and goal in gas carburizing, involving complicated procedures in the
furnace and requiring precise control of many thermal parameters. Based upon diffusion theory and years of
carburizing experience, this paper calculates the effective case depth governed by carburizing temperature, time,
carbon content of steel, and carbon potential of atmosphere. In light of this analysis, carburizing factors at various
temperatures and carbon potentials for steels with different carbon content were calculated to determine the
necessary carburizing cycle time. This methodology provides simple (without computer simulation) and practical
guidance of optimized gas carburizing and has been applied to plant production. It shows that measured effective
case depth of gear parts covering most of the industrial application range (0.020 inch to over 0.250 inch) was in
good agreement with the calculation.
ISBN: 1-55589-010-0 Pages: 7
15FTM04. Single-Piece, High-Volume, Low-Distortion Case Hardening of Gears

Authors: Maciej Korecki, Emilia Wolowiec-Korecka, Doug Glenn
Global output of gears in the automotive industry is estimated to be in excess of 1 billion units per year.
While carburizing and quenching of steel gears for the automotive industry provides the surface-hardened teeth
and flexible core necessary for a long-lasting gear, heat treating, and especially the quenching process, produces
distortion. Distortion is most often corrected by the costly process of post-heat treat machining. The main goal of

every high-volume gear heat treating process is the elimination of distortion. If distortion is not eliminated, the goal
is significant reduction, predictability, and repeatability of distortion.
This article looks at the major causes of deformation during heat treatment and methods for controlling, correcting,
and eliminating distortion. A new concept—a single-piece flow case hardening system—will be presented. This
system adjusts to the size and shape of the particular gear in order to minimize distortion and ensures ideal
repeatability of results, gear after gear. It is a compact system designed for high-volume gear heat treating, is
ideal for lean manufacturing configurations, and can easily be integrated into machining centers.
ISBN: 1-55589-011-7 Pages: 15
15FTM05. Innovative Steel Design and Gear Machining of Advanced Engineering Steel
Authors: Lily Kamjou, Patrik Ölund, Erik Claesson, Joakim Fagerlund, Garry Wicks, Mats Wennmo,
Hans Hansson
The basis for high fatigue performance in high hardness steel originates in precise inclusion engineering. In
addition, recent research shows that by changing the alloying strategy, an increase in the bending fatigue limit can
be achieved similar to an additional shot-peening process. Therefore, the near surface structure will exhibit
excellent mechanical properties and compressive residual stresses in the as-carburized condition.
The current paper describes the potential of clean steel for new approaches in transmission gear box
manufacturing and possibilities to meet the future demands of being smaller, lighter and managing higher torque.
One important factor is the bending fatigue performance of the gear teeth where an increasing fatigue strength is
required. The paper discusses how shot peening might be eliminated in high-cleanliness, as-carburized steel
components using an alternative composition. The fatigue performance of such a solution is compared to
conventional grades used today, both with and without shot peening.
The full benefit of this new steel design can be obtained by using a high-quality steel with a decreased number of
critically-sized inclusions in the loaded volume. Results from extensive testing support how this type of steel
compares to commonly used carburizing steels. The effect of material cleanliness on contact fatigue is also
examined through FZG pitting testing.
To address potential machining issues of clean steels, the paper also deals with the production process, including
quantitative machining trials and the importance of tooling selection. The study is focused on the production of
gears, dealing mainly with turning and hobbing. Initial results show how these clean steels can be machined in full
scale production in standard conditions with equal or better efficiency and cost.
ISBN: 1-55589-016-2 Pages: 12
15FTM06. Powder Metal Gear Technology: A Review of the State of the Art
Author: Anders Flodin
During the past 10 years, the PM industry has put a lot of focus on how to make Powder Metal gears for
automotive transmissions a reality. To reach this goal, several hurdles had to be overcome, such as fatigue data
generation on gears, verification of calculation methods, production technology, materials development, heat
treatment recipes, design development, and cost studies.
All of these advancements will be discussed, and a number of vehicles with powder metal gears in their
transmissions will be presented. How the transmissions have been redesigned in order to achieve the required
stress levels while minimizing weight and inertia, thus increasing efficiency, will also be discussed.
ISBN: 1-55589-017-9 Pages: 11
15FTM07. Industry 4.0 and its Implication to Gear Manufacturing

Author: Hermann J. Stadtfeld
The Industry 4.0 is an initiative of leading German industrial corporations and scientific institutions, supported with
funding from the German government, which promotes the computerization of traditional industries such as
manufacturing. This paper reviews the four industrial periods from the viewpoint of gear manufacturing and points
out the special character of the fourth industrial period, which has just begun. The main part of the paper reports
about the techniques and elements of the so-called cyber physical production systems and how they will change
the way of industrial manufacturing. In the proceeding sections, the paper relates the features of Industry 4.0 to
the Gleason achievements regarding machining process design, machine networking, expert systems, machine
self-diagnosis, and cycle optimization, as well as remote diagnosis. The conclusion points out that the new
movement will enhance manufacturing capabilities, improve product quality, and will create very flexible
manufacturing. Gleason products today already show a significant content of smart features and modern data
processing, which together with a leading strategy for future developments, is represented with the name
Gleason 4.0.
A concern of manufacturing personnel is the missing transparency and traceability of the action that a smart
manufacturing control is executing. The concern, that chaotic situations can occur if the smart manufacturing
system has to react to unexpected input information, is justified; the concern about missing traceability is, in most

cases, not justified. For example, in the early days of G-AGE corrections, gear engineers liked to understand why
the combination of five or more delta settings would correct a certain flank form error. However, the mathematics
behind those corrections are rather complex and would require many hours—or even days—to verify a single set
of correction data. After the first years of practice with G-AGE, gear engineers learned to trust the results and
applied them without questioning. In the few cases when the theory failed and the corrections made the gear
worse, the gear engineer used common sense and either applied simple manually calculated corrections or
eliminated a critical input or output variable in order to unarm the unstable part of the originally computed results.
This example shows that it is efficient to have the thousands of decisions or actions which are constantly
reoccurring done by the smart manufacturing system. Its strength is to execute reoccurring operating tasks very
fast. The human skill is to concentrate on all out-of-the-ordinary situations, in which the computerized intelligence
is not very strong. The artificial neurons don’t take anyone’s workplace. Quite the contrary—future manufacturing
will only exist if it follows the smart movement. Workplaces in factories will be sophisticated and interesting, and
humans will be in control…probably in more control than they have been in the past.
ISBN: 1-55589-018-6 Pages: 24
15FTM08. Proposed Pre-Finish Cylindrical Gear Quality Standard

Author: Peter E. Chapin
It is quite common to specify a gear class for in-process quality requirements, usually calling for a lower quality
class than is required for the finished gear quality. Although it is appropriate to have lower expectations for a pre-
finish gear condition, it is not appropriate to subject the pre-finish gear to the same level of scrutiny as a finished
gear. Gears in a pre-finish condition may have large feed scallops or generating flats, which are desirable for
productivity and may be conducive to the finishing process. However, such features will be evaluated as errors
when subjected to the full analysis as required by the finished gear class inspection. Therefore, the use of a
finished gear quality specification is not recommended or even appropriate for pre-finish gear quality evaluation,
even if the quality class has been adjusted to pre-finish expectations. Additionally, in-process requirements often
require non-zero target helix and profile slopes, which necessitate a new method of analysis to determine the
achieved quality class. Therefore, a pre-finish evaluation method and standard is proposed. This proposed
standard would not make any recommendations regarding the required quality for any application. The intent is to
establish standard pre-finish quality classes for typical finishing operations, which only include the inspection
elements that are important to properly evaluate pre-finish gear quality as it applies to the finishing operation.
ISBN: 1-55589-019-3 Pages: 19
15FTM10. Influence of Hobbing Tool Generating Scallops on Root Fillet Stress Concentrations
Authors: Benjamin S. Sheen, Matthew Glass
In the design of gear and spline teeth, the root fillet area and its maximum tensile stress are of primary concern for
the gear designer. In general terms, the tensile stress in the root fillet is based on specific geometries of the
design: minor diameter, fillet radius, etc. However, additional concerns regarding the manufacturing method,
cutting tool geometry, and process parameters can greatly influence the impact of stress concentration factors in
the root fillet area.
For a hobbed tooth manufacturing process, the root fillet geometry is controlled by the rack design of the cutter,
but also by the number of generating scallops produced by the tool. For a shaping process, the generating
scallops are close together and can produce a surface with almost no visible signs of root fillet generating
scallops. However, for a hobbing process, the number of threads, number of gashes, and tip radius can create
multiple variations of generated scallops. These can create stress concentrations, which can increase the tensile
bending stress and potentially impact the service life of the component. For this discussion, stress concentrations
caused by root fillet generating scallops will be reviewed.
This paper will discuss a specific example regarding parallel-sided splines manufactured with a finish hobbing
process and their effects on generating root fillet stress concentrations. To estimate the value of the stress
concentrations, Finite Element Analysis was performed on the components for two unique hobbing tool designs.
The FE results are compared to actual component field service histories.
ISBN: 1-55589-021-6 Pages: 10
15FTM11. Selecting the Proper Gear Milling Cutter Design for the Machining of High Quality Parallel Axis,
Cylindrical Gears and Splines
Author: Brent Marsh
Gear milling cutters offer a versatile and timesaving solution for milling of high-quality gear profiles. Application
methods vary. There are many ways to utilize these cutters. Machines range from traditional gear hobbing
machines with single indexing capability to horizontal and vertical CNC machining centers with 4- or 5-axis
capability, modern multi-task turning and milling centers, CNC lathes with live milling capability, and dedicated
special-purpose machines.

Tool selection will depend on a number of factors, such as module size, work piece material, gear quality level
desired, spur or helical design, tooth count, size of gear blank, and available equipment options. The desired post-
milling operations needed—such as hardening, grinding, honing, and shaving—also have an influence on the
milling tool design.
When planning for successful process methods, rigidity, tool holding (arbor supported vs. unsupported), and
material removal rate, all must be addressed.
Power and torque requirements as related to gear material, number of passes, cutter design, and diameter, are
very important in the planning phase. Tool selection has a significant impact on this. Rake angles and cutter
geometry are important. Tools are designed according to rough, semi-finish, and finish requirements. Tandem,
multi-cutter designs will improve productivity but bring on specific challenges to the process engineer.
Surface finish requirements are also very important. Milling methods can vary from climb cutting to conventional
milling. Both methods have their place and impact surface finish and tool life. Radial infeed and reduced or
increased feed rate on entry are other factors. Wet-versus-dry machining and oil-versus-water-soluble coolants
impact tool life, part quality, and environmental concerns. Proper chip thickness and calculations for feed rate
compensation must be considered.
This paper takes a comprehensive view of all of the above mentioned topics to assist the manufacturing engineer
or process planner in successfully choosing the design of gear milling cutters to make cost-effective cylindrical
gears to the appropriate quality desired.
ISBN: 1-55589-022-3 Pages: 12
15FTM12. Simulation of Hobbing and Generation Grinding to Solve Quality and Noise Problems
Author: Günther Gravel
Due to increasing tolerance requirements for gearboxes and gears, it has become more and more important to
establish quality circles in production. A quick detection and correction of the causes of tolerance violation is
essential for high quality. This paper shows the possibilities and procedures of searching for the root cause in
general, especially with problems in hobbing and generation grinding using multi-start tools.
A new simulation tool has been developed, which allows for the simulation of typical faults that occur during
hobbing and generation grinding. The calculated contour on the workpiece is treated as a measured curve,
making it easy to compare workpiece measurements and simulations. In this way, possible error causes can be
simulated and compared with the real gear surface.
This paper uses practical examples to demonstrate the following applications for simulation. The influence of the
tool parameter’s "number of starts" and "number of flutes" on the cutting result is shown in connection with the
axial feed parameter. Protuberance and tooth tip rounding on the tool influence the profile form generated on the
workpiece. Wobble and eccentric in the tool clamping creates an s-shaped pattern on the profile, based on the
number of starts on the tool. The form of the pattern changes with different parameters.
In high-speed gearboxes, ripples on the gear surfaces are frequently the cause of noise problems. Simulation of a
tool error and a subsequent evaluation of the ripples enable conclusions to be drawn about the excitations caused
by the tool error during the cutting process. A practical comparison between the ripple measurement of a hobbed
and subsequently honed gear and the simulation shows that the noise-related ripples on the finished part arises
already in the pre-machining stage.
The applications presented in this paper show that the results of the simulation are a very good match with
practical tests. Thus, the simulation software is a highly precise tool for determining and eliminating the causes of
deviations in production. At the same time, design engineers and planners can quickly and easily develop new
process and tool designs, thereby significantly reducing the costs involved in testing.
ISBN: 1-55589-023-0 Pages: 11
15FTM13. Thermal Capacity of a Multi-Stage Gearbox

Authors: Albertus Willem Wemekamp, A. Doyer
In many industrial gearbox applications, thermal rating is a key factor in the practical utilization of the gearbox.
The thermal capacity is affected by the efficiency (power loss) of the gearbox and heat dissipation within the
environment. Methods, as found in ISO Technical Reports (ISO/TR 14179), help to estimate quasi-stationary
temperature in the oil sump.
To further increase the understanding, SKF has incorporated power loss prediction and thermal equilibrium in its
validated simulation tool. It goes beyond ISO methods: it includes the interaction between heat losses, thermal
expansions, and (bearing) pre-loading. With this simulation tool, all these interactions can be analyzed by solving
the mechanical and thermal problem simultaneously.
When changing operating conditions (e.g., during starting up), temperature differences between rotating parts
(e.g., shafts) and the exterior parts (e.g., housing) may differ considerably from the steady state conditions. These
effects are extremely difficult to anticipate, or complex measurements would be required. The developed method

allows engineers to perform transient calculation in which the momentary temperature differences (affecting the
bearing loading) are taken into account. In this way, the whole gearbox behavior can be analyzed in more detail.
In the paper, the methodology used to obtain the interaction between mechanical and thermal equilibrium will be
explained. Using the simulation tool capabilities, the performance of the bearings and gears in a multi-stage
gearbox will be analyzed and presented.
ISBN: 1-55589-025-4 Pages: 12
15FTM14. Gear Backlash Analysis of Unloaded Gear Pairs in Transmissions

Author: Carlos Wink
A best practice in gear design is to limit the amount of backlash to a minimum value needed to accommodate
manufacturing tolerances, misalignments, and deflections, in order to prevent the non-driving side of the teeth to
make contact and rattle. Industry standards, such as ANSI/AGMA 2002 and DIN3967, provide reference values of
minimum backlash to be used in the gear design. However, increased customers’ expectations in vehicle noise
reduction have pushed backlash and allowable manufacturing tolerances to even lower limits. This is especially
true in the truck market, where engines are quieter because they run at lower speeds to improve fuel economy,
but they quite often run at high torsional vibration levels. Furthermore, gear and shaft arrangements in truck
transmissions have become more complex, for an increased number of speeds and to improve efficiency.
Determining the minimum amount of backlash is quite a challenge. This paper presents an investigation of
minimum backlash values of helical gear teeth applied to a light-duty pickup truck transmission. An analytical
model was developed to calculate backlash limits of each gear pair when not transmitting load, and thus
susceptible to generate rattle noise, through different transmission power paths. A statistical approach (Monte
Carlo) was used since a significant number of factors affect backlash, such as tooth thickness variation, center
distance variation, lead, runout and pitch variations, bearing clearances, spline clearances, and shaft deflections
and misalignments. Analytical results identified the critical gear pair, and power path, which was confirmed
experimentally on a transmission. The approach presented in this paper can be useful to design gear pairs with a
minimum amount of backlash, to prevent double flank contact and to help reduce rattle noise to lowest levels.
ISBN: 1-55589-026-1 Pages: 7
15FTM15. New Refinements to the Use of AGMA Load Reversal and Reliability Factors
Author: Ernie Reiter
AGMA standards use load reversal and reliability factors in the calculation of the rated load capacity for gear
teeth. ANSI/AGMA 2101-D04 recommends the use of a load reversal factor of 1.0 for most gears which see one-
way bending, and 0.7 for gears such as idler gears and planet gears that see a fully reversing bending condition.
Likewise, the standard uses a table format to assign a reliability factor based on a desired reliability level in an
application.
This paper suggests two ways to calculate a load reversal factor which would be material specific, based either on
Modified Goodman or Gerber Failure Theories. This paper further provides a method of calculating the reliability
factors which very closely match the AGMA tables found in ANSI/AGMA 2101-D04.
ISBN: 1-55589-028-5 Pages: 15
15FTM17. Homogeneous Geometry Calculation of Arbitrary Tooth Shapes – Mathematical Approach and
Practical Applications
Authors: Maximilian Zimmer, M. Otto, Karsten Stahl,
As an extensive machine element to transfer and convert rotational movement, gears meet high requirements for
construction and assembly. Due to existing modern production techniques, more sophisticated gear types can be
produced with high precision and maintainable financial effort. The benefits of traditional gear profiles, such as an
involute, are thus no longer of major importance. In particular, for gear types such as bevel, worm, and hypoid
gears, but also for non-standard gear types (e.g., beveloid gears, crown gears, or spiroid gearings), modern gear
production systems ensure high quality and reliability to the operator. Depending on the context of application,
different gear types have advantages and disadvantages concerning load carrying capacity, effectiveness, or
noise excitation. Supported by various calculation software tools for the particular gear type, it is possible to create
the optimal gear design, depending on the respective application. A homogeneous calculation software for
ubiquitous gear geometries—irrespective of the gear type, and especially for analyzing non-standard gears—
would be preferable.
This paper provides a mathematical framework and its implementation for calculating the tooth geometry of
arbitrary gear types, based on the basic law of gear kinematics. The rack or gear geometry can be generated in
two different ways: by calculating the conjugate geometry and the line of contact of a gear to the given geometric
shape of a known geometry (e.g., a cutting hob), or by prescribing the surface of action of two gears in contact
and calculating the correspondent flank shapes. Besides so-called standard gears like involute spur and helical
gears, bevel or worm gears, it is possible to analyze the tooth geometry of non-standard gears (e.g., non-involute
spur, conical, or spiroid gears). Depending on the type of gear, a distinction is made between tool-dependent and
tool-independent geometry calculation.

The described mathematical algorithms are summarized in implemented software modules for the particular gear
types. Two practice-oriented examples are presented to illustrate the calculation model: beveloid gears for use in
vehicle or marine gear boxes as well as rack-and-pinion meshing with variable ratio, as it is used for steering
systems on automobiles. Since the geometry is exported as a point cloud, a further analysis of the generated
gear types is possible, e.g., by computer-aided design or finite-element software tools as well as manufacturing
on 5-axis CNC or forging machines. Thus, a detailed analysis—especially of non-standard gears—is feasible that
currently cannot be calculated and evaluated with common industrial gear calculating software.
ISBN: 1-55589-029-2 Pages: 17
15FTM18. Rating of Asymmetric Tooth Gears

Author: Alexander L. Kapelevich
The benefits of gears with asymmetric tooth profiles for unidirectional torque transmission are well known. The
design objective of asymmetric tooth gears is to improve performance of the primary drive flank profiles at the
expense of the opposite coast profiles’ performance. The coast flanks are unloaded or lightly loaded during a
relatively short work period. Asymmetric tooth profiles make it possible to simultaneously increase the contact
ratio and operating pressure angle of drive tooth flanks beyond those limits achievable with conventional
symmetric tooth gears. The main advantage of asymmetric tooth gears is drive flank contact stress reduction,
which allows one to considerably amplify power transmission density, increase load capacity, and reduce size and
weight. However, asymmetric tooth gears and their rating are not described by existing gear design standards.
This paper presents a rating approach for asymmetric tooth gears by their bending and contact stress levels in
comparison with symmetric tooth gears, whose rating is defined by standards. This approach applies finite
element analysis (FEA) for bending stress definition and the Hertz equation for contact stress definition. It defines
equivalency factors for practical asymmetric tooth gear design and rating.
The paper illustrates the rating of asymmetric tooth gears with numerical examples.
ISBN: 1-55589-030-8 Pages: 15
15FTM19. Worm Gear Efficiency Estimation and Optimization

Authors: Massimiliano Turci, E. Ferramola, F. Bisanti, G. Giacomozzi
This paper outlines the comparison of efficiencies for worm gearboxes with a center distance ranging from 28 to
150 mm that have single reduction from 5 to 100:1. Efficiencies are calculated using several standards (AGMA,
ISO, DIN, BS) or by methods defined in other bibliographic references.
It also deals with the measurement of torque and temperature on a test rig, required for the calibration of an
analytical model to predict worm gearbox efficiency and temperature.
There are also examples of experimental activity (wear and friction measurements on a block-on-ring tribometer
and the measurements of dynamic viscosity) regarding the effort of improving the efficiency for worm gear drivers
by adding nanoparticles of fullerene shape to standard PEG lubricant.
ISBN: 1-55589-031-5 Pages: 15
15FTM20. Efficiency of Worm Gear Drives

Authors: Eva-Maria Mautner, W. Sigmund, J.-P. Stemplinger, Karsten Stahl
Due to a wide range of properties, worm gears are an indispensable element on the current transmission market.
Next to a huge gear ratio field in one gear stage of i = 5 to i = 80, operation with low noise and vibration is
realizable. Furthermore, worm gears provide the opportunity of self-locking, respectively self-braking. Despite
these benefits, as a result of greater energy awareness, the efficiency of worm gears is in the focus. Because of
high sliding velocities, especially at high gear ratios, gearing losses are a main topic of interest. Other gearbox
concepts with combined spur and bevel gear sets show smaller gear ratio fields, and therefore the realization of
high gear ratios in only one stage is not possible. Consequently, fewer components are necessary for worm
gearboxes, which allows savings of assembly and maintenance costs.
In the scope of recent research projects, the efficiency and the load-carrying capacity of worm gears is examined.
Therefore, experimental investigations on different worm gears were conducted on several test rigs. Generally,
the pairing of bronze worm wheel with case-hardened worm is used in center distances between a = 65 and 315
mm. Additionally, the influence of different gear ratios, worm wheel materials, lubricants, and contact pattern on
efficiency and load-carrying capacity are considered. In the course of these investigations, overall worm gearbox
efficiencies of up to η = 96% are reached.
The paper describes the conducted tests in detail and shows basic examples of experimental test results. On the
basis of the experimental investigations and theoretical examinations, recommendations for an increase in
efficiency are given.
ISBN: 1-55589-032-2 Pages: 22

15FTM21. Polish Grinding of Gears for Higher Transmission Efficiency
Author: Walter Graf
This paper introduces a new gear polish grinding process and describes its multiple benefits to makers of
automotive transmissions. First, based on independent scientific studies and customer trials, it will be shown that
improved surface finishes increase the overall efficiency of transmissions, which translates into a reduction in
torque loss, lower fuel consumption, and lower CO2 output. The resulting higher bearing ratios reduce micro-
pitting, and thus increase the longevity of gears. Secondly, the paper introduces a cost-efficient manufacturing
method adapted for large-scale manufacture, as automotive transmission manufacturers need a more suitable
method than the time-consuming vibration finishing used in aerospace applications today.
ISBN: 1-55589-033-9 Pages: 13
15FTM22. A New Class of Industrial Gear Oil

Authors: David B. Gray, René Koschabek, Aidan Rose
Industrial gear oils are a critical component in the efficient operation of modern equipment. More than 800 000
tons of these industrial gear oils are sold each year, which accounts for 5–6% of the total industrial lubricants
market.
While industrial gear oils have not traditionally been the leading focus for lubricant development, the recent strong
growth of wind turbines and field service performance has shifted the focus significantly in the direction of the
industrial gear oils.
The challenging application for gearboxes in wind turbines has created demand for new high performance
synthetic gear oils that provide both good equipment protection and longer drain intervals. While recent years
have seen lubricant performance improvements, the highly fragmented landscape of OEM requirements and the
complex approval processes have limited the application’s attractiveness to those developing new lubricant
formulations.
Today, however, the leading synthetic gear oils are based principally on polyalphaolefins (PAO), and while these
lubricants are very effective and durable, they come at a significant cost penalty when compared to conventional
mineral oils.
This has created an opportunity for a new class of industrial gear lubricants, based on alternative synthetic
materials. These new industrial gear oils have been developed to satisfy critical market performance expectations,
ensure global supply chain security, and to address economic as well as performance challenges.
This paper describes the technical aspects of this novel synthetic gear oil lubricant approach.
ISBN: 1-55589-034-6 Pages: 11
15FTM23. Noise Reduction in an EV Hub Drive Using a Full Test and Simulation Methodology
Authors: Owen J. Harris, P.P. Langlois, G.A. Cooper
With the current trend towards Electric Vehicles (EVs), there is likely to be increasing focus on the noise impact of
the gearing required for the transmission of power from the electric motor (high speed) to the road. Current
automotive Noise, Vibration and Harshness (NVH) understanding and methodologies for total in-vehicle noise
presuppose relatively large Internal Combustion (IC) contributions compared to gear noise. Further, it may be
advantageous to run the electric motors at significantly higher rotational speed than conventional automotive IC
engines putting the gear trains into higher speed ranges. Thus, the move to EV or Hybrid Electric Vehicles (HEV)
places greater or different demands on gear train noise.
This work combines both a traditional NVH approach (in-vehicle and rig noise, waterfall plots, Campbell diagrams,
and Fourier analysis)—with highly detailed transmission error measurement and simulation of the complete
drivetrain—to fully understand noise sources within an EV hub drive.
The transmission error testing has been performed on both the full assembly with the three-stage gear train and
on individual gear pairs using a dedicated transmission error measurement rig. Highly accurate rotary encoders
are used to measure transmission error through different stages of the gear train in order to identify sources of
excitation.
For comparison, a full Computer-Aided Engineering (CAE) model has been built, which includes the flexibilities of
all components, gears, shafts, bearings, and casing. Standard analysis is used to simulate the system deflection
under input loads with corresponding gear misalignments, contact patches, and transmission errors. Contact
patches are compared to tooth marking test results. Further, a novel advanced calculation is performed which
iteratively couples deflections of the full system model with detailed tooth contact analysis at the gear meshes.
This analysis shows how the gear meshes and the deflections of the full transmission change through the gear
meshing cycles. This analysis can include detailed, measured, manufactured gear geometry, and various
tolerances and errors within the system and calculate both the associated individual mesh and system
transmission errors and their harmonic content.

Detailed test and simulation identifies the noise sources to be the meshes of the three gear sets and captures a
full understanding of them. Methods are presented to accurately derive and compare the individual gear mesh
transmission errors from test and simulation of the complete unit. Further analysis of the individual results
indicates both gear design and manufacturing considerations to be optimized to reduce noise. The results of
prototype testing of design changes are given showing significant in-vehicle noise reductions.
A detailed methodology is presented, combining both a full series of tests and advanced simulation to
troubleshoot and optimize an EV hub drive for noise reduction.
ISBN: 1-55589-035-3 Pages: 22
15FTM24. Tribological Coating Wear and Durability Performance Guideline for Gear Applications
Authors: Randy Kruse, Carl Hager, Ryan D. Evans
Diamond-like carbon (DLC) tribological coatings have demonstrated the ability to provide gear and bearing
performance enhancements in an initially narrow but increasing range of applications. These experiences have
heightened awareness and curiosity in industry about the potential of DLC coatings to enhance the performance
of gear train systems. Valuable benefits may include reducing the probability of micropitting wear and increasing
scuffing resistance, perhaps even to enable improved oil-out performance in aerospace applications. The
application of these coatings may be used to increase gearbox efficiency, not by reducing friction within tooth
contacts, but by increasing tooth surface durability to allow for less viscous lubricants and reduced lubricant
quantities.
It is generally known that extreme contact pressure and sliding velocity operating conditions can lead to coating
wear. However, a better understanding of the thresholds that constrain coating durability and usefulness are
needed so that gear and bearing engineers can more accurately specify and predict system life. This paper
reports the results of testing a tungsten carbide-reinforced diamond-like carbon coating (W-DLC) as applied to
AISI 4320 and AMS6308 gear materials using a rotating ball-on-disk tribology test rig under a range of conditions
that simulate the contact stresses and sliding velocities of gears.
ISBN: 1-55589-036-0 Pages: 13
15FTM25. An Experimental Evaluation of the Procedures of the ISO/TR 15144 Technical Report for the
Prediction of Micropitting
Authors: Donald R. Houser, Samuel Shon
This paper presents the results of several experimental analyses to explore some of the features and
methodologies of ISO 15144. A summary of ISO 15144 is first discussed, as is a spreadsheet that has been
written, to accept contact stresses calculated from load distribution analyses. Sample load distribution analyses
and subsequent ISO predictions are made for several experimental results that are reported in the literature.
Following these analyses, a series of experimental durability tests were run using the AGMA tribology gears
running with Dexron 6 automatic transmission fluid as the lubricant. An FVA 54 test was run to obtain the lubricant
pass/fail level and the permissible value of Lambda needed to calculate the safety factor for micropitting.
ISBN: 1-55589-037-7 Pages: 18
15FTM26. Calculating the Risk of Micropitting Using ISO Technical Report 15144-1:2014 – Validation with
Practical Applications
Authors: Burkhard Pinnekamp, Michael Heider
Micropitting is a surface fatigue phenomenon on highly loaded gears with case-hardened gear flanks. Main
contributors are local stress, surface roughness, sliding speed, and lube oil properties.
General influence factors, testing, and earlier calculation methods were described in 11FTM15 [1]. Meanwhile, a
new version of the ISO Technical Report, TR 15144-1:2014 [2], was issued. It is intended to become an ISO
Standard within the next years.
This paper describes the definition of micropitting, the actual calculation method, and its application to practical
examples where micropitting has either occurred or not. The examples give evidence that the Technical Report
reliably predicts the risk of micropitting where it is later found on the gear flanks. For cases where no micropitting
occurs, the calculated safety factors are sufficiently high. Operating conditions for some examples are out of the
validated range of the Technical Report.
ISBN: 1-55589-038-4 Pages: 16
15FTM27. Wear: A New Approach for an ‘Old’ Failure Phenomenon of Gears

Authors: Ulrich Kissling, Sandro Hauri
Wear is a well-known criterion of failure for gears. Wear is a result of metallic contact between the tooth flanks.
But when a lubricant is involved, the wear-generating mechanism can be quite different. If the pitch line velocity is
0.5 m/s or higher, the lubrication film still has a dominant effect, the metallic contact is only partial, and the gears
are running in the mixed-film or full EHL regime. At very low pitch line velocities (less than 0.5–1.0 m/s), the
boundary lubrication prevails, and the metallic contact is dominant. The wear behavior in this case is completely

different from wear occurring in mixed-film regime. Wear occurring at very slow speed is called in U.S. literature
‘slow-speed wear’ or ‘adhesive wear’ [1]. In German literature also, the term ‘cold wear’ [2] (in contrast to scuffing,
which is sometimes called ‘hot wear’) is used. In this paper, slow-speed wear will be discussed, defined as the
following: wear occurring either on lubricated gears at very low pitch line velocity or on dry-running gears.
Wear on gears is not an intensely researched topic, so little literature can be found. When compared with the
exhaustive investigations carried out on other phenomena such as macropitting, scuffing, micropitting, or tooth
flank breaking, it seems that slow-speed wear has literally been left out! But despite this, there are applications in
heavy gear applications where wear is a criterion that cannot be ignored.
Worldwide, until 2014, only one standard existed, AGMA 925 [3], which describes wear and proposes a method to
evaluate the risk of wear. As will be discussed further on, the wear described by AGMA 925 is the wear occurring
in the mixed-film regime; wear at very slow speed is not covered by AGMA 925.
In a quite different area of application, wear is a very important topic—for dry running plastic gears. Over the past
few years, the authors have worked closely with a number of manufacturers of plastic gears and the University of
Erlangen (Germany) to investigate the problems of gear wear in detail. A calculation method could be developed
that can be used to predict where and when local wear will occur on a tooth flank. Parts of these findings have
also just been published in the final version of the German standard VDI 2736 [4].
The basic mechanics of slow-speed wear of metallic gears is the same as for dry-running plastic gears. However,
the wear coefficients to be applied in each case are very different, and the influence of the lubricant (in particular,
the effect of the lubricant additives) is crucial. In 1980, at the FZG in Munich, Plewe [5] published investigations of
the adhesive wear behavior of lubricated metallic gears (pitch line velocities 0.007–1.0 m/s). The wear coefficients
were determined for additive-free oil. However, a "factor for the influence of lubrication" is required before Plewe's
data can be used for a modern gear lubricant, and up to now, very little is known about these factors.
If the wear coefficient is known, the distribution of wear can be defined over the tooth contact area in the contact
analysis. If the step-by-step change in the tooth flank (due to wear) is then also taken into account, a realistic
prediction of the progression of wear and its effects on noise and vibrations can be made.
ISBN: 1-55589-039-1 Pages: 15
15FTM28. Application of Advanced Mesh Analysis to Eliminate Pinion Failures

Author: Terry Klaves
This paper will walk through a case study involving pinion failures on plastic extruder drives. It will cover failure
analysis, gear rating review, application of advanced mesh analysis to define component deflections causing
loaded mesh misalignment, and reduced tooth contact/high stress concentration resulting in tooth macropitting.
The paper will demonstrate the capability and benefits of advanced mesh analysis, including design of optimized
microgeometry and application of said microgeometry through precision tooth form grinding, with
recommendations on types of microgeometry which are most effective, easiest to apply, inspect, and document in
a production gear manufacturing environment. The summary will review tools which are commercially available to
perform advanced mesh analysis, design, manufacture, and inspect optimized microgeometry—which
compensates for tooth deflection, shaft bending, torsional windup, and bearing deformation in order to improve
gearing mesh alignment and tooth contact under load for quiet running and longer life gearing. This tool can be
applied proactively at the design phase to optimize gearing performance or reactively to identify root cause of
failures and recommend corrective action.
ISBN: 978-1-55589-042-1 Pages: 10
15FTM29. Tooth Flank Fracture – Influence of Macro and Micro Geometry

Author: Stefan Beermann
In this paper, the method to calculate the risk of tooth flank fracture, which is defined in the current draft of ISO
DTS 19042-1, is investigated and discussed. Part of this investigation is a sensitivity analysis with respect to the
main gear parameters. Therefore, parameters including pressure angle, helix angle, normal module, hardness
depth, tip relief, and crowning were systematically varied and the respective safety factor against tooth flank
fracture was calculated.
With this method, it can be shown that the risk of tooth flank fracture and the risk of pitting might have opposite
trends. It is also shown that a tip relief on spur gears typically has no effect or might even increase the risk of tooth
flank fracture. On helical gears, the situation is more complex. For lead modifications, a certain beneficial effect is
seen by compensating misalignments of the flanks; however, if the modification chosen is too large, it will increase
the risk of tooth flank fracture.
In the first part of the paper, some formulas of the draft are discussed. There, it is shown that the definition of the
material factor and the calculation of the course of the hardness into the depth of the material could be improved.
ISBN: 1-55589-043-8 Pages: 11

2014 PAPERS
14FTM01 Molecular Decomposition Process = Electrochemical Assisted Precision Form Grinding
Author: J.A. DeAngelo
Molecular decomposition process (MDP) is an anodic dissolution process (electrochemical) whereby the work
piece is the anode and the grinding wheel is the cathode. Specific controls of electrical, mechanical and chemical
actions are applied to enable the MDP system to remove stock without mechanical or thermal deformation. This
process enables stock removal rates in sample materials such as nickel and titanium alloys to occur at rates more
aggressively than conventional creep-feed grinding. Migrating the system to employ super-abrasives greatly
increases the rate of stock removal. The anodic process implemented permits the perishable wheel geometry to
be preserved which equates to longer perishable life and dimensional stability, which enables longer production
runs with consistent dimensional results.
MDP has proven to produce gear involute geometries from “as supplied” blanks with minimal stock for finishing.
Roughing and finishing of forms in full hardened 4140 tool steel yielding an MDP produced product with surfaces
to less than 1 Ra µin while maintaining dimensional stability to achieve a 1.67 CPK. The MDP system removes
large or small amounts of stock while providing a safe work environment for operators and the environment.
ISBN: 1-61481-093-3 Pages: 11
14FTM02 Prediction of Surface Zone Changes in Generating Gear Grinding

Authors: F. Klocke, M. Brumm, J. Reimann, M. Ophey
One possible process for hard finishing gears is generating gear grinding. Due to high process efficiency
generating gear grinding has replaced other grinding processes like profile grinding in batch production of small
and middle sized gears.
Despite the wide industrial application of generating gear grinding, the process design is based on experience and
time and cost intensive trials. The science-based analysis of generating gear grinding needs a high amount of
time and effort and only a few published scientific analyses exist. In addition, the transfer of existing knowledge
from other grinding processes onto generating gear grinding is complicated due to the contact conditions between
tool and gear flank, which change continuously during the grinding process.
One research objective for generating gear grinding is to increase economic efficiency and productivity of the
process. At the same time gear quality must be equal or higher and the external zone must not be damaged. But
especially the influence of the grinding process on the external zone in generating gear grinding is unknown. In
case of an inappropriate process design in combination with stock deviations an unrequested process result or
even a thermal damage of the external zone can occur. In this report a thermo-mechanical process model, which
describes influences on the surface zone in generating gear grinding, is introduced.
ISBN: 1-61481-094-0 Pages: 15
14FTM03 Surface Roughness Measurements of Cylindrical Gears and Bevel Gears on Gear
Inspection Machines
Author: G. Mikoleizig
Alongside the macro test parameters on tooth flanks for profile and tooth traces, surface properties (roughness)
play a decisive role in ensuring proper toothed gear function.
The generally increased load stresses on gear teeth can only be implemented by maintaining precisely defined
roughness parameters.
Roughness measurements are therefore conducted on the gearing flanks in all highly developed drives, in the
automotive industry, aircraft industry, or the area of wind energy drives, for example.
This article addresses roughness measurement systems on tooth flanks. In addition to universal test equipment,
modified test equipment based on the profile method for use on gears is addressed in particular. The equipment
application here refers to cylindrical gear flanks and bevel gear flanks.
ISBN: 1-61481-095-7 Pages: 13
14FTM04 Reliable Measurements of Large Gears

Authors: M. Stein, K. Kniel, F. Härtig
Large gears have become an indispensable part of modern technical applications. The expanding industrial
sectors of power generation and transmission, like shipbuilding industry, wind turbine generators and petroleum
conveying systems, have led to an increasing demand for large scale gear boxes. Thus, the qualified
measurement of large gears has become more and more important as well. Their conformance with specifications
according to ISO 14253-1 [1] has to be proved, which is not possible without a qualified statement of the task-
specific measurement uncertainty. As a consequence, the manufacturing processes cannot be controlled
quantitatively and at a reasonable process capability level, especially if tolerances are small compared to the
achievable measurement uncertainty. This specifically applies to large gears.

In this report three current projects are outlined and presented with a comparison for large involute gears. The
measurement results are presented. As a second step towards traceable measurements of large gears, a special
calibration laboratory shall be established. This is part of a joint research project, within which also a new
measurement standard of 2 m in diameter has been developed. Lastly, information about a Joint Research Project
within the European Metrology Research Program which will start in September 2014 is provided.
ISBN: 1-61481-096-4 Pages: 10
14FTM05. A Different Way to Look at Profile and Helix Inspection Results

Author: J.M. Rinaldo
The traditional inspection of involute gear profile and helix deviations results in plots of deviations from a perfect
involute and from a perfect helix. While this is appropriate for gears with an unmodified profile or helix, it is not
ideal for gears that have intentional modifications. This paper explores the advantages of looking directly at
deviations from the design shape. This type of analysis is implied but not explicitly stated nor is it pictured in the
new edition of ISO 1328-1. Also presented is a modification to zone based tolerance evaluation as presented in
ISO 1328-1:2013, with limits on the total deviation from design given graphically.
ISBN: 1-61481-097-1 Pages: 7
14FTM06. High Contact Ratio Gearing: A Technology Ready for Implementation?

Author: C.D. Schultz
Today’s competitive industrial gear marketplace demands products with excellent reliability, high capacity, and low
noise. Surface hardened ground tooth gearing predominates but the legacy tooth forms handicap further
improvements in capacity and noise generation. Vehicle and aircraft equipment use tooth forms not found in the
standard charts to achieve better performance at little or no increase in cost. This paper will propose adopting
these high contact ratio forms to industrial use.
ISBN: 1-61481-098-8 Pages: 13
14FTM07. A Case Study in a Practical Application of Smart Gearbox Technology

Author: A.J. Soder
The purpose of the paper is to discuss the development of smart gearbox technology using real-world application
testing and data analysis, while keeping in mind the needs of the end-user in order to assist them in developing
their monitoring system. It will describe the previous maintenance methodologies used and how the ever-changing
needs of the industry require them to introduce a proactive maintenance system rather than a typically reactive
approach.
It will explain the testing performed at the user’s facility which helps gather the data that cannot be duplicated on a
test system. It will then explain how after all the data is reviewed and analyzed, it is then relayed back to the user
so it can be implemented by their maintenance departments. It will discuss reviewing the data of a failed gearbox
during testing and how looking at the data can give a glimpse of how to understand what the data is telling us in
regards to the end goal of the project
ISBN: 1-61481-099-5 Pages: 11
14FTM08. The Efficiency of a Simple Spur Gearbox – A Thermally Coupled Lubrication Model
Authors: A.I. Christodoulias, A.V. Olver, A. Kadiric, A.E. Sworski, F.E. Lockwood
A thermally coupled efficiency model for a simple dip-lubricated gearbox is presented. The model includes
elastohydrodynamic friction losses in gear teeth contacts as well as bearing, seal and churning losses. An iterative
numerical scheme is used to fully account for the effects of contact temperature, pressure and shear rates on EHL
friction. The model is used to predict gearbox efficiency with selected transmission oils whose properties were first
obtained experimentally through rolling-sliding tribometer tests under representative contact conditions.
Although the gearbox was designed using standard methods against a fixed rating, the model was used to study
efficiency over a much wider range of conditions. Results are presented to illustrate the relative contribution of
different sources of energy loss and the effect of lubricant properties on the overall gearbox efficiency under
varying operating conditions.
ISBN: 1-61481-100-8 Pages: 18
14FTM10. Involute Spiral Face Couplings and Gears: Design Approach and Manufacturing Technique
Authors: A.L. Kapelevich, S.D. Korosec
Face gears typically have a straight or skewed tooth line and varying tooth profile in normal cross section at
different radii from major to minor diameter. These face gears are engaged with spur or helical involute pinions at
intersecting or crossed axes.
This paper presents spiral face gears with involute tooth line and identical tooth profile in the normal section at any
radius. There are two main applications for such face gears. One of them is an alternative solution with certain
advantages in performance and fabrication technology to the straight tooth, Hirth, or Curvic flange couplings.
Another application is when a face gear is engaged with an involute helical pinion or worm at intersecting or
crossed axes. Such engagement is also used in Helicon® type gears.

The paper describes gear geometry analysis, and design technique of spiral face involute gears with symmetric
and asymmetric tooth profiles. It also explains a highly productive hobbing method of these gears and tool design
specifics, and illustrates gear and tool design with numerical examples.
ISBN: 1-61481-102-2 Pages: 9
14FTM11. Mathematical Modeling for the Design of Spiroid®, Helical, Spiral Bevel and Worm Gears
Author: G. Kazkaz
This paper will present a novel work for spiroid and worm gears that mathematically calculates the gear tooth
profile in terms of the geometry of the machining tool (hob) and the machining setup. Because of similarity, the
work was also expanded to spiral bevel gear. We have developed software to plot the gear tooth when the
parameters of the geometry of the tool and machining setup are entered. The gear tooth shape can then be
altered and optimized by manipulating the input parameters until a desired tooth profile is produced. In effect, the
result will be designing the hob and machining setup for best gear tooth profile on the computer. Afterward, the
generated gear tooth data are entered into CAD software to generate a true 3D model of the gear. The tool path
will also be generated from the data for CNC machining instead of hobbing.
ISBN: 1-61481-103-9 Pages: 16
14FTM12. Optimization of Gear Tooth Contact by Helix Angle Modification

Authors: S. Hipsley, R.J. Davey, R.T. Wheway
This paper reports the results of a study of the effects of helix angle modification on the load distribution and
stresses within teeth of helical gears, and the calculation of appropriate compensation for torsional effects.
Load distribution and peak stress for helical gears under normal torsional forces inherent in helical gear drives are
significantly influenced by the flexibility of the gear body, tooth structure and elastic deformation of the contact
surfaces. Uncompensated, these factors reduce the gear face contact area and accordingly increase maximum
stress and decrease pitting resistance and bending strength power ratings.
This paper transforms the calculation of the compensation required by translating the underlying analysis into a
MATLAB based program that can be run on a modest, standard PC computer. Informed practicing engineers – as
opposed to esoteric experts in whose domain these calculations currently reside – now have a tool to do the
necessary calculations with ease.
The results from the program are confirmed by FEA analysis of compensated and uncompensated examples,
together with a practical example with an operating, 3,000 kW gearbox. The results show that the program
produces the appropriate adjustment, such that the contact areas are full width across the gear faces. The
authors’ recommendation is, now that a user-friendly analysis tool is available, that helix angle compensation
should be included in rating standards.
ISBN: 1-61481-104-6 Pages: 13
14FTM13. A Practical Approach for Modeling a Bevel Gear

Author: B. Bijonowski
The modern bevel gear design engineer is often faced with knowing the basic appearance of the bevel gear tooth
that he is designing. The geometry of the bevel gear is quite complicated to describe mathematically, and much of
the overall surface topology of the tooth flank is dependent on machine settings and the cutting method employed.
AGMA 929-A06, Calculation of Bevel Gear Top Land and Guidance on Cutter Edge Radius, lays out a practical
approach for predicting the approximate top land thicknesses at certain points of interest regardless of the exact
machine settings that will generate the tooth form. The points of interest that AGMA 929-A06 is concerned with
consists of toe, mean, heel, and the point of involute lengthwise curvature.
The following method expands upon the concepts described in AGMA 929-A06 to allow the user to calculate not
only the top land thickness, but the more general case, the normal tooth thickness anywhere along the face and
profile of the bevel gear tooth. This method does not rely on any additional machine settings; only basic geometry
of the cutter, blank, and teeth are required to calculate fairly accurate tooth thicknesses. The tooth thicknesses are
then transformed into a point cloud describing both the convex and concave flanks in a global Cartesian
coordinate system. These points can be utilized in any modern computer aided design software package to assist
in the generation of a 3D solid model. All pertinent macro tooth geometry can be closely simulated using this
technique. Furthermore, a case study will be presented evaluating the accuracy of the point cloud data to a
physical part.
ISBN: 1-61481-105-3 Pages: 17
14FTM14. Theoretical and Experimental Study of the Frictional Losses of Radial Shaft Seals for
Industrial Gearbox
Authors: M. Organisciak, P. Baart, S. Barbera, A. Paykin M. Schweig
In this paper SKF presents an engineering model for the prediction of radial lip seal friction based on a physical
approach. The friction model includes the generation of friction due to rubber dynamic deformation and lubricant

viscous shear between the surfaces of a seal and a shaft. The friction model is coupled with a heat generation
and seal thermal model. Indeed, seal friction and seal temperature are closely related: the heat generated in the
sealing lip is conducted through the seal and shaft and dissipated into the environment. This changes for instance
the lubricant viscosity.
The model is verified step by step in an extensive experimental study. Measurements of seal friction, seal
temperature and lubricant film thickness have been performed for various dynamic lip seals. The analyzed
parameters are: surface speed, oil viscosity, seal material, seal size, seal lip style and duty cycles. The correlation
between model predictions and experimental friction measurements can therefore be verified.
ISBN: 1-61481-106-0 Pages: 12
14FTM15. Application of a Unique Anti-Wear Technology – Ion-Sulfurized Lubricating Gradient Material

Authors: G. Wang, Y. Zhang, X. Zhang, H. Liu
This Ion-sulfurization, also called plasma sulfurization, is a state-of-the-art technology conferring excellent anti-
friction and wear-resistant characteristics on metallic parts including gears, splines, and bearings. It is
characterized by a sulfur-proliferated zone composed of sulfides and sulfur-metal solid solution case with smooth
sulfur compositional gradient towards the underlying substrate. Varity of metals and alloys, including steels, cast
irons, super-hard alloys, and bronze, are suitable for ion-sulfurization. This treatment is carried out at low
temperature, so that geometric integrity, microstructure and mechanical characteristics of the substrate are not
impaired. Ion-sulfurized gears and bearings shorten the run-in time span of the machinery/automotive units. Even
more, the contact fatigue in gears and splines can be noticeably reduced. Another distinguished engineering
advantage is, the tribological property of the sulfide layer on steel can survive a temperature as high as 2000°F,
which is rarely surpassed by other lubricants.
In this article, the engineering characteristics of ion-sulfurization are introduced. Exemplary application is provided
as reference for those interested in this technology
ISBN: 1-61481-107-7 Pages: 13
14FTM16. The Modified Life Rating of Rolling Bearings – A Criterion for Gearbox Design and
Reliability Optimization
Authors: A. Doyer, A. Gabelli, G. Morales-Espejel
This The concepts of rolling bearing rating life and basic load rating (load carrying capacity) were introduced by
Arvid Palmgren in 1937 [1]. At that time, until the 1950s, most bearing manufacturers listed in their catalogues the
load admissible on the bearing for thousands hours of operation at five different speeds. In those days the
selection of a bearing size for a given application was a rather simple and approximate matter.
The concept of a single rating factor to characterize the dynamic capacity of the bearing was new and initially
used only within the bearing company that developed this new technology. This rating method was backed by the
theory of Lundberg & Palmgren (L-P) [2] and by the Weibull statistics [3]. It was found that it could provide a
correct interpretation of the many series of endurance tests available at the time, [2], [4], [5]. This calculation
method prevailed on all the others methods used at the time and was adopted by ISO in 1962.
ISBN: 1-61481-108-4 Pages: 16
14FTM17. The Impact of Surface Condition and Lubricant on Gear Tooth Friction
Authors: S. Rao, A. Isaacson, G. Sroka, L. Winkelmann
Frictional losses in gear boxes are of significant interest to gear box designers as these losses transform into
heat. The direct result is a reduction in the fuel efficiency of the vehicle involved. Further, in many instances, this
heat has to be absorbed and dissipated so that lubricant properties and gear box performance are not significantly
compromised. This effort is to measure and document the comparative friction losses in a gear mesh due to gear
tooth surface condition and lubricant. Three distinct surface conditions are considered. They are ground, Isotropic
Superfinished (REM ISF®) and tungsten-incorporated diamond-like carbon coating (W-DLC). Two lubricants, MIL-
PRF-23699 and Mobil SHC 626 lubricants are considered.
The experimental effort is conducted on a high speed, power re-circulating (PC), gear test rig, which had been
specially instrumented with a precision torque transducer to measure input torque to the 4-square loop. The
torque required to drive the loop is measured under various speeds and tooth loads within the torque loop, with
test gears with different surface conditions and with different lubricants. Two operating torque levels within the
4-square loop at speeds ranging from 4,000 rpm (pitch-line velocity of 19 m/sec) to 10,000 rpm (pitch-line velocity
of 47 m/sec) are evaluated.
Based on the collected data a qualitative analysis of the effect of gear tooth surface condition on frictional losses
is presented. Further, the surface characteristics of the tooth flanks of the ground, superfinished and coated gears
are also described.
ISBN: 1-61481-109-1 Pages: 9

14FTM18. Precision Bevel Gears with Low Tooth Count
Authors: S.P. Radzevich, V.V. Irigireddy
The paper deals with the geometry and kinematics of right-angle bevel gears that feature low tooth count. Right-
angle bevel gears are a particular case of intersected-axis gearing (further Ia - gearing) with an arbitrary value of
shaft angle. In this paper, gears that have 12 teeth and fewer are referred to as the low-tooth-count-gears (or LTC
- gears, for simplicity).
When operating, right-angle bevel gears often generate vibration and produce an excessive noise. Dynamic
loading of the gear teeth can result in the tooth failure. These problems become more severe in bevel gearings
with low tooth count. The performed analysis shows that inequality of base pitches of the gear and mating pinion
is the root cause for insufficient performance of LTC - gears.
In most applications, the main purpose of Ia - gearing is to smoothly transmit a rotation and torque between two
intersected axes. Gear pairs that are capable of transmitting a uniform rotation from the driving shaft to the driven
shaft are referred to as the geometrically accurate intersected-axis gear pairs (or, in other words, the ideal
intersected-axis gear pairs).
ISBN: 1-61481-110-7 Pages: 12
14FTM19. Application of ICME to Optimize Metallurgy and Improve Performance of Carburizable Steels
Authors: J. Grabowski, J. Sebastian, A. Asphahani, C. Houser, K. Taskin, D. Snyder
QuesTek Innovations LLC has applied its Materials by Design® computational design technology and its
Integrated Computational Materials Engineering (ICME)-based methods to successfully design, develop and
implement two new high-performance gear steels (Ferrium® C61™ and Ferrium C64® steels) that are being used
in demanding gear and bearing applications in ground and aerospace military, commercial aerospace, high-
performance racing, oil & gas and other industries. Additionally, QuesTek has successfully designed and
developed two new high-performance structural steels (Ferrium S53® and Ferrium M54® steels). All four Ferrium
alloys are commercially available from Carpenter Technology and have been awarded SAE AMS numbers for
procurement. QuesTek has also designed several other high performance alloys using ICME technologies,
including a stainless nitridable bearing and gear steel and alloys for additive manufacturing applications.
ISBN: 1-61481-111-4 Pages: 10
14FTM20. Influence of Central Members Radial Support Stiffness on Load Sharing Characteristics of
Compound Planetary Gear Sets
Authors: Z. Peng, S. Wu
In this study, a non-linear dynamics model of Ravigneaux compound planetary gear set which adopts the
intermediate floating component is set up based on concentration parameter. By considering the position errors
and eccentric errors, the dynamic load sharing factors of the gear set are calculated. The relationship between
central members radial support stiffness and the dynamic load sharing factors is obtained and the influence of
central members radial support stiffness on load sharing characteristic is analyzed. The research results show
that central members radial support stiffness effect obvious to the gear pairs which are directly contacted to the
central members, while the effect is rather small to the gear pairs which are not directly connected. Reducing the
radial support stiffness of the central members helps improve the load sharing performance of the system.
ISBN: 1-61481-112-1 Pages: 12
14FTM21. On the Correlation of Specific Film Thickness and Gear Pitting Life
Author: T. Krantz
The effect of the lubrication regime on gear performance has been recognized, qualitatively, for decades. Often
the lubrication regime is characterized by the specific film thickness defined as the ratio of lubricant film thickness
to the composite surface roughness. It can be difficult to combine results of studies to create a cohesive and
comprehensive dataset. In this work gear surface fatigue lives for a wide range of specific film values were studied
using tests done with common rigs, speeds, lubricant temperatures, and test procedures. This study includes
previously reported data, results of an additional 50 tests, and detailed information from lab notes and tested
gears. The dataset comprised 258 tests covering specific film values [0.47 to 5.2]. The experimentally determined
surface fatigue lives, quantified as 10-percent life estimates, ranged from 8.7 to 86.8 million cycles. The trend is
one of increasing life for increasing specific film. The trend is nonlinear. The observed trends were found to be in
good agreement with data and recommended practice for gears and bearings. The results obtained will perhaps
allow for the specific film parameter to be used with more confidence and precision to assess gear surface fatigue
for purpose of design, rating, and technology development.
ISBN: 1-61481-113-8 Pages: 18

2013 PAPERS
13FTM01. Power Skiving of Cylindrical Gears on Different Machine Platforms
Author: H.J. Stadtfeld
Skiving is a cutting process which was first patented in 1910 as an efficient process to manufacture internal ring
gears. Like honing, Power Skiving uses the relative sliding motion between two “cylindrical gears" whose axes are
inclined. The skiving cutter looks like a shaping cutter with a helix angle for example, 20� different than the helix
angle of the cylindrical gear to be machined.
The skiving process is multiple times faster than shaping and more flexible than broaching, due to the continuous
chip removal in skiving, but it presents a challenge to machines and tools. While the roll motion between the
cutting edge and the gear slots occurs with the spindle RPM, the relative axial cutting motion is only about one
third of the circumferential speed of the cutter. The cutting components of rolling and cutting which result in a
“spiral peeling" are represented with the process designation skiving.
Because of the relatively low dynamic stiffness in the gear trains of mechanical machines as well as the fast wear
of uncoated cutters, skiving of cylindrical gears never achieved a breakthrough against shaping or hobbing until
recently. The latest machine tools with direct drive train and stiff electronic gear boxes present an optimal basis for
the skiving process. Complex tool geometry and the latest coating technology were required to give the soft
skiving of cylindrical gears a breakthrough. Gleason has developed a line of dedicated power skiving machines,
which apply solid HSS cutters for small to medium modules.
ISBN: 978-1-61481-058-2 Pages: 18
13FTM02. Performance and Technological Potential of Gears Ground by Dressable cBN Tools
Authors: J. Reimann, F. Klocke, M. Brumm, A. Mehr and K. Finkenwirth
Dressable vitrified bond cBN grinding tools combine the advantages of other common tool systems in generating
gear grinding. The cBN grains are a highly productive cutting material due to their high specific stock removal rate.
Vitrified bonds are dressable and thereby very flexible: By dressing different profile modifications can be set up
and constant gear quality can be guaranteed during the tool life time. Despite those technological advantages
there is only a small market distribution of these grinding tools due to high tool costs. Furthermore, only a few
published scientific analysis of generating gear grinding with dressable cBN exist. Especially, the influence of the
grinding tool system on manufacturing related component properties has not been analyzed yet. The research
objective of this report is to determine the advantages of dressable cBN tools in generating gear grinding.
ISBN: 978-1-61481-059-9 Pages: 12
13FTM03. Analysis of Gear Root Forms: A Review of Designs, Standards and Manufacturing Methods for
Root Forms in Cylindrical Gears
Authors: N. Chaphalkar, G. Hyatt, and N. Bylund
Gear root is an important but often neglected element of the gear. The stress concentration point typically lies in
the tooth to root transition area and it is this point that determines the life or the fatigue life of a gear in many
applications. Specific standards are in place on design of the involute part of a gear tooth, the root area however
is less standardized. New manufacturing methods enable the designer of gears greater latitude in the design of
strong alternative root forms. The standards on design and specification for the root geometry are lax so these
root forms fit into current standards.
This paper reviews the designs of various root forms for the gears. It compares the various root forms on basis of
their strength, fatigue resistance and other parameters. This analysis will be based on compilation of various
research previously conducted on gear root forms.
The paper also discusses current manufacturing methods to produce the roots, and recently introduced
alternatives. It will compare the traditional methods with new methods of gear manufacturing it terms of types of
roots produced and overall control over the root profile.
ISBN: 978-1-61481-060-5 Pages: 9
13FTM04. Best Practices for Gearbox Assembly and Disassembly

Author: J. Bello
When industry is looking at the best ways to increase efficiency, reduce downtime and increase profitability,
gearbox performance and reliability are key factors. In most applications gearbox reliability is critical to the
productivity of the overall plant operation. Repair is often required with a swift turn around, as down time is very
expensive. Designing for repair, and writing effective repair procedures, can speed the service time, and provide a
quality refurbishment. Minimizing down time and extending service life will contribute significantly to achieving the
lowest overall operation costs.
The best practices listed below are proven, effective methods used to install and remove bearings, seals, gears,
couplings and shafts within a gearbox. These techniques are not new, and are usually obtained by hard won
experience. Collecting them in one location is an attempt to document the best practices and provide a reference

for design engineers. Engineers write the procedures for assembly and disassembly, they also dictate to the rest
of the design team the design intent. Including features to facilitate disassembly, minimizes repair cycle time and
helps to prevent damage to components that could radically compromise their design life or performance.
ISBN: 978-1-61481-061-2 Pages: 11
13FTM05. Cubitron™ II: Precision Shaped Grains (PSG) Turn the Concept of Gear Grinding Upside Down
Author: W. Graf
To date, grinding, according to the German DIN Standard 8580, is “machining with geometrically undefined cutting
edges" while other machining processes such as turning and milling are classified as processes with
“geometrically defined cutting edges". New abrasive grains, called PSG and developed by 3M, stand this definition
on its head. For the first time, grinding wheels made with PSG, called Cubitron™ II, can claim to be made up of
“geometrically defined cutting edges" as each and every grain is exactly the same engineered shape. Hence, it
might be more appropriate to talk about “micro-milling" rather than grinding. This is borne out by looking at the
resulting “flowing" chips which are akin to chips seen in milling operations, just finer.
These free-flowing chips no longer clog up the grinding wheel and, therefore, the grinding wheel remains free-
cutting and dressing becomes only necessary due to loss of from rather than loss of cutting ability. In repeated
tests, this has shown to drastically reduce the risk of burning and to give consistent and predictable results.
Furthermore, tests and subsequent long term trials under production conditions have shown that grinding time can
be cut in most cases by at least 50% in comparison to grinding wheels made of standard ceramic abrasives.
Based on more than 100 carefully monitored and documented gear grinding trials, this paper will demonstrate how
Cubitron™ II grinding wheels work both in continuous generating grinding of car and truck gears, and in form
grinding of large diameter gears for wind generators, for example. Furthermore, the paper will discuss chip
formation, filmed with high resolution slow motion; and the benefits of the free-flowing chips in terms of resulting
consistent surface finish, superior form holding and extended dressing cycles.
ISBN: 978-1-61481-062-9 Pages: 10
13FTM06. High Gear Ratio Epicyclic Drives Analysis

Author: A. Kapelevich
Epicyclic gear stages provide high load capacity and compactness to gear drives. There is a wide variety of
different combinations of planetary gear arrangements [1, 2]. For simple epicyclic planetary stages when the ring
gear is stationary, the practical gear ratio range varies from 3:1 to 9:1. For similar epicyclic planetary stages with
compound planet gears, the practical gear ratio range varies from 8:1 to 30:1.
This paper presents analysis and design of epicyclic gear arrangements that provide extremely high gear ratios.
Using differential-planetary gear arrangements it is possible to achieve gear ratios of several hundred to one in
one-stage drive with common planet gears and several thousand to one in one-stage drive with compound planet
gears. A special two-stage planetary arrangement may utilize a gear ratio of over one hundred thousand to one.
This paper shows an analysis of such uncommon gear drive arrangements, defines their major parameters,
limitations, and gear ratio maximization approaches. It also demonstrates numerical examples, existing designs,
and potential applications.
ISBN: 978-1-61481-063-6 Pages: 12
13FTM07. Finite Element Analysis of a Floating Planetary Ring Gear with External Splines
Authors: V. Kirov and Y. Wang
This study investigates the stresses and deflections of a floating ring gear with external splines working in a large
planetary wheel motor of a mining truck. Such calculations carried out with conventional engineering approaches
described in popular standards and textbooks are not comprehensive because of the complexity of the problem.
These approaches can give us good stress numbers for non-floating gears and some guidance about the rim
thickness factor but they lack the capabilities to effectively calculate the deflections and their influences on the
stresses, especially for floating gears. Moreover, they cannot calculate an entire gearing system and the
interdependent influences of the different components.
The model studied consists of a floating ring gear driving a torque tube. The ring gear is driven through internal
gear meshing by three planets and it transmits the torque to the torque tube through its external splines. The
torque tube transmits the motion to the hub and the truck tires. A nonlinear static analysis of the ring gear and
torque tube was conducted in ABAQUS. Linear 8-node hex elements and linear tetra elements were used to
model the ring gear and torque tube. External torque was resolved into corresponding tangential force, which was
then applied directly onto three of the ring gear's internal teeth. Contact pairs were used to capture the load
transfer between the ring gear and torque tube through the splines.
The results show that the deflections in the ring gear were so excessive that about one-tenth of the spline teeth
were actually transmitting torque against the common engineering understanding that only half of the spline teeth
are typically engaged. The crowning of the spline teeth had also effect on the stresses though quite small

compared to the deflections. Conclusions and recommendations were made about the effectiveness of the
design.
ISBN: 978-1-61481-064-3 Pages: 11
13FTM08. Application and Improvement of Face Load Factor Determination Based on AGMA 927 (Accurate
and Fast Algorithm for Load Distribution Calculation, for Gear Pair and Planetary Systems, Including Duty
Cycle Analysis)
Author: U. Kissling
The face load factor KHβ, which in rating equations represents the load distribution over the common face width in
meshing gears, is one of the most important items for a gear strength calculation. In the international standard for
cylindrical gear rating, the ISO 6336-1, using method C, some formulas are proposed to get a value for this factor.
But as the formulas are simplified, the result is often not very realistic. Also AGMA 2001 (or AGMA 2101)
proposes a formula for KHβ, different from ISO 6336, but again not always appropriate. Therefore, a note in AGMA
stipulates, that “it may be desirable to use an analytical approach to determine the load distribution factor".
In the last edition of ISO 6336 (2006), a new annex E was added: “Analytical determination of load distribution".
This annex is entirely based on AGMA 927-A01. It is a well-documented procedure to get a direct and precise
number for the face load factor. Today an increasing number of gear designers are using tooth contact analysis
(TCA) methods to get precise information over the load distribution on the full gear flank. Contact analysis is very
time consuming and does not permit to get a value for KHβ, as defined by the ISO or AGMA standard. A contact
analysis result combines different factors of ISO 6336 as KHβ, KHα, Zε, Zβ, ZB, ZD and buttressing effects, etc., thus
to `extract' KHβ from a TCA is not possible.
The use of the algorithm, as proposed by AGMA 927, is a good solution to get proper values for KHβ; it is simpler
and therefore much quicker than a contact analysis calculation. The paper explains how this algorithm can be
applied for classic gear pair rating procedure, for ratings with complex duty cycles and even for planetary systems
with interdependent meshings between sun, all planets and ring.
ISBN: 978-1-61481-065-0 Pages: 19
13FTM09. Investigations on Tooth Root Bending Strength of Case Hardened Gears in the Range of High
Cycle Fatigue
Authors: N. Bretl, S. Schurer, T. Tobie, K. Stahl and B.-R. Höhn
Tooth root load-carrying capacity is one of the determining factors in gear design. In addition to the strength of the
material itself, the existing state of stress significantly influences tooth root load-carrying capacity.
Based on extensive experimental investigations of gears, the beginning of the fatigue strength range is generally
set 3×106 load cycles, which common calculation methods, like ISO 6336, also take into account. According to
this, standard test methods for tooth root bending endurance strength usually assume a load cycle limit of 3-6 106.
However, current as well as completed studies on tooth root load carrying capacity show tooth root fractures with
relatively high numbers of load cycles in a range of general fatigue strength and above. Analysis of these fracture
surfaces shows that these late breakages are often initiated by small inclusions or microstructural defects in the
material. These tooth fractures that initiate with cracks under the surface have a negative effect on the tooth root
load-carrying capacity in the range of high cycle fatigue. Therefore, experimental investigations regarding high
cycle fatigue have been carried out in a pulsator test rig on gears of various sizes, materials and residual stress
conditions. As a result, depending on the existing residual stress condition, there are different levels of tooth root
load carrying capacity, different failure behaviors in high cycle fatigue and different types of damage. Especially
for test variants with high residual stresses, the size of the gear and the cleanness of the material have an impact
on the tooth root load-carrying capacity and the damage pattern.
This paper discusses the different fracture modes by means of examples. Furthermore, it presents the influence of
residual stresses, size and material cleanness on the tooth root load-carrying capacity and on the type of tooth
root fractures with crack initiation on and under the surface. These influences will be additionally confirmed by
examples of experimental test results.
ISBN: 978-1-61481-066-7 Pages: 16
13FTM10. Calculation of the Tooth Root Load Carrying Capacity of Beveloid Gears
Authors: C. Brecher, M. Brumm and J. Henser
In this paper, two developed methods of tooth root load carrying capacity calculations for beveloid gears with
parallel axes are presented. The first method calculates the tooth root load carrying capacity in an FE-based
approach. The initial step of the method is the manufacturing simulation in the WZL software GearGenerator. The
manufacturing simulation calculates the 3D geometry of the beveloid gears by simulating the generating grinding
process. The next step is an FE-based (finite element) tooth contact analysis with the WZL software ZaKo3D
which is able to calculate the tooth root stresses of several gear types during the meshing. From these stresses

and further parameters (e.g., local material properties) the tooth root load carrying capacity is calculated in an
approach which is based on the weakest link model of Weibull.
The second method uses analytic formulas to calculate the tooth root load carrying capacity of beveloid gears. In
this method the tooth root load carrying capacity of beveloid gears is compared to the tooth root load carrying
capacity of cylindrical gears. The effects which are observed during this comparison are described and formulas
are derived to take these effects into account. Finally, both methods are applied to a test gear. The methods are
compared to each other and to tests on beveloids gears with parallel axes in test bench trials.
ISBN: 978-1-61481-067-4 Pages: 19
13FTM11. Striving for High Load Capacity and Low Noise Excitation in Gear Design
Authors: K. Stahl, M. Otto and M. Zimmer
In the design process of gearboxes, common requirements are high load capacity and low noise excitation.
Reaching both goals is laborious and normally requires a trade-off. Detailed analyses of contact conditions and
deformations are necessary. These should take place in an early design stage to realize a mostly straightforward
design approach and prevent late design changes. Focused on cylindrical gears, the paper covers an approach
starting at the first draft of a gearbox.
Defining the macrogeometry of the teeth regarding load capacity calculation according to standards leads to a
reasonable gear design. On that basis, the micro geometry of the teeth is specified and load distribution as well as
noise excitation is calculated. The design parameters are interdependent so provisions have to be made to adjust
each step on the remaining ones. Effects resulting from changing profile contact ratio under load and contact
patterns not covering the whole flank have to be regarded. The beneficial effect of a modified microgeometry is
dependent on the ability to precisely account for contact conditions and meshing clearances.
To find an optimal solution for the competing goals of capacity and excitation, detailed calculation methods are
required. To be able to apply latest research results, these are implemented in highly specialized software. The
task described above is handled by using the software that was developed at the Gear Research Center (FZG)
with funding by the German Research Association for Gears and Transmissions (FVA). The underlying calculation
methods and analyzed phenomena are covered.
ISBN: 978-1-61481-068-1 Pages: 14
13FTM12. Practical Considerations for the Use of Double Flank Testing for the Manufacturing Control
of Gearing
Authors: E. Reiter and F. Eberle
The gearing industry has developed many unique measuring techniques for the production control of their
products. Each technique has inherent advantages and limitations which should be considered by designers and
manufacturers when selecting their use. Double flank composite inspection, (DFCI) is one such technique that can
functionally provide quality control results of test gears quickly and easily during manufacturing. The successful
use of DFCI requires careful planning from product design, through master gear design and gage control methods
in order to achieve the desired result in an application.
This document explains the practical considerations in the use of double flank testing for the manufacturing
control of spur, helical, and crossed axis helical gearing including:
- a general description of double flank inspection equipment including an explanation of what can
be measured;
- recommendations on practical master gear design;
- the calculation of tight mesh center distance and test radius limits;
- the resulting backlash that can be anticipated in gear meshes based on applying double flank tolerances in a
design;
- initial and ongoing statistical techniques in double flank testing and how they can be practically used to
improve gear quality;
- double flank gage measurement system analysis including case studies of gage repeatability and
reproducibility (R&R) and uncertainty analysis.
ISBN: 978-1-61481-069-8 Pages: 32
13FTM13. Gear Failure Analysis and Lessons Learned in Aircraft High-Lift Actuation
Authors: A. Wang, S. Gitnes, L. El-Bayoumy and J. Davies
Several gear failure cases and lessons learned in the development phase of aircraft high lift actuation systems are
presented, including leading edge geared rotary actuators, and trailing edge geared rotary actuators, sector gears
and pinions, and offset gearboxes. The high lift system of an aircraft, which contains trailing edge flaps and/or
leading edge slats, increases lift for takeoff, controls flight during cruise, and reduces speed while increasing lift
for shorter landing distance.
Many of these components contain highly loaded gears to increase the power to weight ratio. Because of
requirements on weight or envelope and consideration of cost, the gears are always designed to the limit with

reasonable margins of safety in a high lift system. The structure which supports the gears is limited in size and
simplified, and the gear material and heat treatment are selected for easy manufacturing. Therefore, when
misalignment and/or deflection of the gears are large enough to cause reduction in tooth contact area, the stress
on gears becomes large enough to cause damage. The failure modes can be classified as spalling or pitting at the
location of concentrated loads. Most of the problems can be resolved by providing correct lead modification to
alleviate the concentrated loading, while some need increase of the gear diameters, design modifications, or
introduction of materials with higher allowable.
ISBN: 978-1-61481-070-4 Pages: 15
13FTM14. Metallurgical Investigation of “Tiger Stripes" on a Carburized High Speed Pinion

Authors: M. Li, P. Terry, and R. Eckert
“Tiger stripes" on a high speed pinion made of carburized SAE 9310 steel were investigated. The stripes were on
lines of action on the load side of the teeth coinciding with different angular positions of the gear mesh. Scanning
Electron Microscopy (SEM) of the affected areas showed fused metal particles, with a diameter of 1–3 microns,
and gas pockets. The morphology of the damage was typical of electric discharge damage shown in ANSI/AGMA
1010-E95. This indicates that the stripes were in fact electric discharge damage. Microhardness surveys on a
metallurgical transverse section of a tooth showed a hardness loss due to the discharge, with load side surface
hardness even lower than 58 HRC. The cause of the “tiger stripes" and potential damage to the gear tooth were
analyzed.
ISBN: 978-1-61481-071-1 Pages: 7
13FTM15. White Structure Flaking in Rolling Bearings for Wind Turbine Gearboxes
Authors: H. Uyama and H. Yamada
Bearing failures in wind turbine gearboxes were investigated and rolling contact fatigue tests to reproduce them
using a hydrogen-charge method were conducted. Two main failure modes in wind turbine gearbox bearings were
white structure flaking and axial cracking, which were involving a microstructural change. Both failure modes can
be reproduced by using specimens charged with hydrogen. Operating conditions, which can induce hydrogen
generation from lubricant and penetration of the bearing steel were discussed. Effects of bearing material on white
structure flaking life were suggested as one of the countermeasures.
ISBN: 978-1-61481-072-8 Pages: 13
13FTM16. The Anatomy of a Lubrication Erosion Failure – Causation, Initiation, Progression and Prevention
Authors: R.J. Drago, R.J. Cunningham, W. Flynn
Visual examination of a compressor box revealed that the Low Speed (LS) Pinion exhibited pitting type defects on
each of its forty-seven (47) helical teeth. Review of the failed component revealed a somewhat repetitive type of
damage at one end of the teeth only. Each tooth showed what appeared to be one defect at a similar location
3600 around the Pinion. Each defect was located within ~0.5 inch of the end of the helical tooth. It was noted that
each tooth defect was observed on the coast side of the teeth only.
Visual examination of the mating gear revealed no evidence of similar damage. While of and by itself, this pitting
may not be cause for alarm, debris from the pitting can adversely affect other components in the gearbox,
especially the bearings, and the stress concentration effect of the pitting, even though it is on the coast flank,
could lead to partial tooth fracture in the region of the distress.
This paper presents a discussion of the causation, diagnosis and metallurgical failure investigation of this
lubrication erosion failure. Our effort was aimed at identifying the nature of the pitting and providing
recommendations to avoid repeat instances of this failure in this specific application and in other future designs for
similar applications.
The subject is presented by way of the discussion of detailed destructive metallurgical evaluations of this specific
lubrication erosion failure which the authors have conducted in order to analyze and characterize the failures.
Lubrication erosion is generally limited to helical gears but the authors have also found this type of distress when
evaluating damage to carburized, hardened and hard finished spiral bevel gears as well when operated under the
“right" circumstances. Lubrication erosion observed on helical gears only, however, will be addressed in this
presentation. Although a specific failure “case" is used as the vehicle for presentation, information has been
extracted and condensed from several individual actual failure investigations conducted by the authors so that a
better understanding of the specific conditions that lead to micropitting and the actual progression from
micropitting to fracture can be presented.
ISBN: 978-1-61481-073-5 Pages: 30
13FTM17. Dynamic Simulations of Radial Lip Seals Followability in an Industrial Gearbox

Authors: M. Organisciak, R. Iervolino, M. Sansalone, S. Barbera, A. Paykin and M. Schweig
Industrial gear units are widely used in power transmission systems. They are composed of shafts, gears, rolling
elements bearings and dynamic lip seals. The seals performance is critical for a proper functioning of the system.
Water or contamination ingress into a mechanical system may lead to a premature failure. Leakage of oil may

have the same effect and be harmful for the environment. Depending on the application, seals may need to
operate under various dynamic conditions, such as wide range of rotational speed (RPM) and temperatures,
shaft–to–bore–misalignment (STBM), shaft dynamic run-out (DRO) or global structure deformations.
The prediction of dynamic seal performance is a complex task. The rotating lip seals are usually made in
elastomeric materials which display a hyper-elastic and viscoelastic behavior. Combined with the dynamic
operating conditions, the simulation of the seal performance requires time dependent approaches which are very
often time consuming. Innovative modeling methods need to be developed in order to be usable by the
development engineering community.
This paper presents a novel approach to predict seal dynamic performance under dynamic conditions. A
formulation of viscoelastic super-elements is developed to predict the deformations of the seal lips. It is combined
with a contact solver to assess contact force and its distribution around the shaft and other lip contersurfaces
(such as other radial or axial locations). In order to demonstrate functionalities and advantages of the developed
method, please consider an example of radial lip shaft seal. The problem addresses prediction of seal
performance at cold temperature, large shaft-to-bore misalignment and dynamic run-out conditions. Different
material and spring options are assessed in order to improve the performance.
This unique modeling capability will allow selecting or developing the shaft seals which would meet and exceed
modern gearbox demanding application. It will also enable gearbox manufacturers to bring to the market more
performing and reliable gearboxes.
ISBN: 978-1-61481-074-2 Pages: 10
13FTM18. Gear Lubrication – Long Term Protection for Wind Turbines

Authors: S. Mazzola, M. Hochmann and J. Wald
The chemical and physical properties of gear oils in use may change more or less depending on its formulation
and the operating conditions. For this reason, a gear oil was investigated after three years of use in a wind turbine
to find out if changes are evident and if the protection of the gears and rolling bearings still meet the requirements
as with fresh oil. Beside chemical and physical analyses, the used gear oil was examined on a FZG back-to-back
gear test rig and on a FE8 test rig. The test results could show that the used gear oil as well as its ability to protect
the gears and rolling bearings has changed very little compared to fresh oil.
ISBN: 978-1-61481-075-9 Pages: 17
13FTM19. Gear Resonance Analysis and Experimental Verification Using Rapid Prototyped Gears
Authors: S.R. Davidson and J.D. Hayes
Determination of gear resonance frequencies is necessary in the design of light weight aerospace gears.
Resonant frequencies and mode shapes calculated are then identified as damaging or non-damaging and
compared to the gear's mesh frequencies to determine if gear tooth bending stresses will be amplified in a
particular operating speed range. Finite Element Analysis (FEA) is well suited to determining gear resonant
frequencies and modes. In order to verify the analysis quickly, rough gear geometry is fabricated and tested using
accelerometers and a calibrated hammer in a modal excitation test. In past efforts, rough geometry fabricated was
a simplified version of the final part minus gear teeth or other features. To reduce the time of fabrication and to
increase the accuracy of the prototype part, modern rapid prototyping manufacturing techniques may hold
promise in approaching the realism of the actual part with material properties that are similar to material properties
of gear steels.
This paper studies gear resonance modal excitation testing of two stage idler spur gear rapid prototyped parts,
using two different rapid prototyping techniques and compares results to the final production part and FEA model.
Damaging and non-damaging modes and nomenclature will be reviewed as well as the testing method.
ISBN: 978-1-61481-076-6 Pages: 11
13FTM20. Influence of Gear Loads on Spline Couplings

Authors: C.H. Wink and M. Nakandakari
Involute splines are commonly used in gearboxes to connect gears and shafts, especially when high torque is
transmitted through the coupling. The load is shared among multiple teeth around the coupling circumference
resulting in higher load capacity than a conventional single key. However, the total load is not equally shared
among all spline teeth, mainly because of pitch deviations resulting from the manufacturing process. The load
distribution along the spline engagement length is also non-uniform because of tooth misalignments and shaft
torsional effects. A typical modeling assumption is that pure torsion load is applied to the spline coupling. In
gearbox applications, when splines are used to connect a gear to a shaft, the torque is transmitted from the gear
teeth in mesh to the shaft, or vice-versa, through the coupling. The gear loads, such as tangential and radial
loads, can affect the load distribution of spline teeth. This paper presents an investigation on the influence of spur
gear loads on load distribution of spline teeth. A generalized analytical model was developed to include external
gear loads on spline couplings. The method divides the spline teeth into stations in the tooth axial direction, and
calculates the load applied to each station based on separation between the mating points. A constant for tooth

stiffness was used to calculate tooth deflections. The load distribution problem was solved using a simple
approach from industry gear standards. The method was implemented into a spreadsheet for numerical example
analyses. The results showed significant effect of side clearance, which is the difference between the space width
of internal spline grooves and external spline tooth thickness, on the maximum load applied to the spline teeth.
The greater the side clearance, the greater is the maximum load applied to the spline teeth. The proposed method
may be helpful to quickly assess load distribution of spline teeth in gear applications, to determine tooth stresses,
and to define lead modifications as needed.
ISBN: 978-1-61481-077-3 Pages: 14
13FTM21. How to Spec a Mill Gear

Author: F.C. Uherek
For optimal torque delivery as a function of cost, there are critical parameters that need to be communicated to
the gear designer from the mill builder when designing gear drive systems for ore grinding applications. Apart from
loads and speeds, interface dimensions and site specific conditions are also needed. Deciding up front which gear
rating practice to select can affect the torque capacity of the drive train by ~15%. How to deliver the torque to the
mill pinion, either by a gear reducer or low speed motor, influences the distribution of cost between the prime
mover and the gear train. This paper will outline the design considerations that go into construction of the drive
system in order to explain why specific data is required and where design freedom is necessary. A clear
specification up front that allows for matching interface dimensions while allowing for the most cost efficient up
front design achieves this goal.
ISBN: 978-1-61481-078-0 Pages: 14
13FTM22. Heat Treatment of Large Components

Author: G.L. Reese
Large gear components can be offered in many applications such as in marine, wind power, steel rolling mills,
power plants, transportation, railroad, aircraft, cement crushers, mining and oil industry applications. There are
three important surface hardening methods used to improve and expand the technical use of gear components.
Design and material engineers must decide which hardening method to use. Case hardening is normally the first
choice because of the highest load capacity. But, case hardening also poses challenges that must be
acknowledged. Therefore, it is good to know that there are three options for very large components.
ISBN: 978-1-61481-079-7 Pages: 21
13FTM23. Ductile Iron for Open Gearing – A Current Perspective

Authors: F. Wavelet and M. Pasquier
For over three decades, open gearing for many applications has been successfully designed and manufactured
from ductile iron. Examples spanning a full range of size and transmitted power are in service in various process
industries throughout the world, proving the soundness of this material selection in technical as well as
economical terms.
The latest metallurgical and manufacturing developments have re-established the practical limits for this material,
well beyond what was considered possible as recently as a few short years ago. A ductile iron gear of 16 m
diameter, 340 BHN (min.) hardness, module 42, with a face width of 1200 mm and having AGMA Q10 teeth
quality, capable of transmitting 2x10 000+ kW was previously a concept. Today, such a gear can be
manufactured. Despite its long and successful service history, ductile iron remains a somewhat lesser known
commodity as an open gearing material.
The goal of this paper is to present the current “state-of-the-art" with respect to ductile iron as a gear material,
including its mechanical properties as applicable to gear design, structural characteristics, typical manufacturing
and inspection plans, and in-service behavior. For each of these aspects, ductile iron will be compared to other
available materials for open gearing design and manufacture, such as cast
ISBN: 978-1-61481-080-3 Pages: 20
13FTM24. Innovative Induction Hardening Process with Preheating for Improved Fatigue Performance of
Gear Component
Author: Z. Li
Contact fatigue and bending fatigue are two main failure modes of steel gears. Surface pitting and spalling are two
common contact fatigue failures, which are due to the alternating subsurface shear stresses from the contact load
between two gear mates. When a gear is in service under cyclic load, concentrated bending stresses exist at the
root fillet, which is the main driver of bending fatigue failures. Heat treatment is required to increase the hardness
and strength of gears to meet the required contact and bending fatigue performance. Induction hardening is
becoming more popular due to its process consistency, reduced energy consumption, clean environment, and
improved product quality. It is well known that an induction hardening process of steel gears can generate
compressive residual stresses in the hardened case. Compressive residual stresses in the hardened case of tooth
flank benefit the contact fatigue performance, and residual compression in the root fillet benefits the bending

fatigue. Due to the complex gear geometry, the residual stress distribution in the hardened case is not uniform,
and different induction hardening process can lead to different residual stress pattern and significant variation of
fatigue performance. In this paper, an innovative approach is proposed to flexibly control the magnitude of
residual stress in the regions of root fillet and tooth flank by using the concept of preheating prior to induction
hardening. Using an external spur gear made of AISI 4340 as an example, this concept of innovative process is
demonstrated with finite element modeling, using commercial software DANTE.
ISBN: 978-1-61481-081-0 Pages: 13
13FTM25. Press Quenching and the Effects of Prior Thermal History on Distortion during Heat Treatment
Author: A.C. Reardon
Precision components such as industrial bearing races and automotive gears often distort unpredictably during
heat treatment due to the deleterious effects of free or unconstrained oil quenching. Press quenching is a method
that can be utilized to minimize the distortion of these complex components during heat treatment. This is
accomplished in a quenching machine by utilizing specialized tooling for generating concentrated forces to
constrain the movement of the component during oil quenching. When performed correctly, this method of
quenching can often achieve the relatively stringent geometrical requirements stipulated by industrial
manufacturing specifications. It can be performed on a wide variety of steel alloys. These include high carbon
through-hardening grades such as AISI 52100 and A2 tool steel, as well as low carbon carburizing grades such as
AISI 3310, 8620, and 9310. The relevant aspects of this specialized quenching technique will be presented
together with a case study of the effects of prior thermal history on the distortion that is generated during press
quenching.
ISBN: 978-1-61481-082-7 Pages: 9
13FTM26. Vacuum Carburizing Large Gears

Author: N. Plough
Vacuum carburizing of gears has typically been limited to parts with relatively small cross-sections. Most alloys
currently in use require oil quenching to achieve adequate surface hardness and core properties in large gear
applications. Pit or large batch IQ furnaces with endothermic atmospheres are often used to process this type of
gear. The majority of vacuum carburizing equipment is designed for processing smaller parts with a high pressure
gas quench. Recent equipment and process developments allow vacuum carburizing and oil quenching of very
large gears and pinions – up to 70" diameter and 7,000 lbs. Fixture design and careful process control help
minimize distortion, while providing the case uniformity and surface integrity that is unique to vacuum carburizing.
This paper will discuss specific case studies involving large gears and pinions. Distortion, case hardness profiles
and microstructures from conventional gas carburizing and vacuum carburizing will be examined and compared.
ISBN: 978-1-61481-083-4 Pages: 7
2012 PAPERS
12FTM01. Balancing – No Longer Smoke and Mirrors
Author: R. Mifsud Hines
In the late 1970's a balancing machine salesman visited a customer's plant who had just received a new balancer
from the salesman's competitor. The plant manager said they were very happy with their automatic balancing
machine and offered to show it to the salesman. The manager walked the salesman out on the floor and the two
of them watched the operator and balancer in action.
The operator placed a part on the balancer and closed the door. The balancer spun up the part, welded on a
weight, spun up again, and displayed “good part.” The operator removed the balanced part, put in a new part, and
closed the door. The balancer spun up the part, welded on a weight, spun up again, and displayed “good part.”
This scenario was repeated several more times as the salesman and the manager watched.
The manager commented, “We just love our new machine. All day long it balances parts by welding on weights
and puts out good parts.” The salesman suggested having the operator place a “balanced part” back in the
balancer again just to see what would happen. So the operator placed the previously balanced part back in the
balancer again and closed the door. The balancer spun up the part, welded on a second weight, spun up again,
and displayed “good part.” The manager had the operator take another balanced part and put it into the balancer
again. Again, the balancer spun up the part, welded on another weight, spun up again, and displayed “good part.”
Suddenly the manager was not so happy with his balancing machine. It seems this machine was not balancing
the parts at all. They had purchased an expensive welding machine to weld weights on their parts.
ISBN: 1-978-61481-032-2 Pages: 10
12FTM02. Power Loss and Axial Load Carrying Capacity of Radial Cylindrical Roller Bearings
Authors: S. Söndgen, W. Predki
The application of cylindrical roller bearings (CRB) is widely spread in mechanical engineering. CRB can carry
comparatively high loads and are usable in high speed ranges. These bearings have been proven to be variously
applicable and economic. With lipped inner and outer rings CRB permit the transmission of axial loads in addition

to radial loads. The axial load is induced on the lip of the inner or the outer ring and transferred by the roller end
face contacts to the opposing lip. In comparison to an only radially loaded bearing there are additional friction
losses in the contact between the lip and the roller ends as a result of sliding.
The limiting factors for the permissible axial load are high temperatures which can cause smearing and seizing, lip
fracture, fatigue failure and wear. In consequence of the axial loading the stresses in the contact between the
roller and the raceway rise and the fatigue durability of the bearing is reduced.
At high speeds the permissible thrust load is dominantly limited by high temperatures. At low speeds the limiting
factors are lip fracture and wear.
Within the examination an extensive test program with different bearing geometries is carried out. Thereby the
decisive measure is the friction torque of the bearings.
The friction torque of a thrust loaded radial cylindrical roller bearing is mainly dependent on the parameters speed,
load, size and design of the bearing.
An analytical simulation model which has been developed at the institute allows calculating the lubrication
conditions, the stresses within the lip-roller contact and the axial load dependent friction torque.
The intention of the study is to enlarge the application range of radial cylindrical roller bearings by means of a
more precise determination of the thrust load capacity and to allow more economic designs.
ISBN: 1-978-61481-033-9 Pages: 11
12FTM03. Gear Lubrication – Gear Protection also at Low Oil Temperatures

Author: M. Hochmann
To find out if the high-performance gear oils of today are able to reliably protect gears and rolling bearings in
gearboxes against damage also at a reduced oil temperature of 40�C, different high-performance gear oils were
examined on an FZG back-to-back gear test rig as well as on an FE8 bearing test rig by modifying the
standardized test methods. It has been shown that the advanced additive technologies used in today's high-
performance gear oils are capable of inducing the required reactions on the surfaces of gears and bearings also
at 40°C, thus providing reliable damage protection even under these operating conditions.
ISBN: 1-978-61481-034-6 Pages: 15
12FTM04. Energy Efficient Industrial Gear Lubricants

Authors: D. Blain, A. Galiano-Roth, R. Russo, K. Harrington
Global energy demand is predicted to be about 30 percent higher in 2040 compared to 2010. Energy demand
growth will slow as economies mature, population growth moderates and efficiency gains accelerate. This paper
will focus on the third factor: energy efficiency. The industrial sector consumes almost 48% of global energy, with
the remainder being used for residential/commercial and transportation. Clearly, improvements in energy
efficiency in the industrial setting can have a major impact on overall global energy use and resultant CO2
emissions.
There are multiple sources of lubricant-related energy loss in industrial equipment in general, and gearboxes in
particular. These include frictional losses due to metal-to-metal contact, frictional traction losses under elasto-
hydrodynamic lubrication conditions and windage/churning loses in the bulk oil. All three of these factors can be
improved by using a properly formulated lubricant, with carefully selected base oils and additives to improve
efficiency.
ExxonMobil has developed a series of industrial lubricants that can reduce energy usage by up to 4% relative to
conventional lubricants. These savings have been documented in both carefully controlled laboratory testing and
in extensive evaluations in actual industrial equipment in the field. Experiments to measure lubricant-related
energy efficiency benefits are inherently challenging. Valid determinations of these benefits require precise
measurements and controls, meticulous attention to detail and appropriate statistical analysis. In addition to the
energy efficiency benefits, these oils can reduce equipment operating temperatures, resulting in increased
component and lubricant life. This leads to longer oil drain intervals, and less used oil disposal.
ExxonMobil defines sustainability as having three components: social development, economic growth and
environmental protection. In addition to discussing all of the points above, this paper will also describe how the
new energy efficient lubricants contribute to each of these sustainability attributes.
ISBN: 1-978-61481-035-3 Pages: 16
12FTM05. Combined Effects of Gravity, Bending Moment, Bearing Clearance, and Input Torque on Wind
Turbine Planetary Gear Load Sharing
Authors: Y. Guo, J. Keller, W. LaCava
This computational work investigates planetary gear load sharing of three-mount suspension wind turbine
gearboxes. A three dimensional multi-body dynamic model is established, including gravity, bending moments,

fluctuating mesh stiffness, nonlinear tooth contact, and bearing clearance. A flexible main shaft, planetary carrier,
housing, and gear shafts are modeled using reduced degrees-of-freedom through modal compensation. This drive
train model is validated against the experimental data of Gearbox Reliability Collaborative for gearbox internal
loads. Planet load sharing is a combined effect of gravity, bending moment, bearing clearance, and input torque.
Influences of each of these parameters and their combined effects on the resulting planet load sharing are
investigated. Bending moments and gravity induce fundamental excitations in the rotating carrier frame, which can
increase gearbox internal loads and disturb load sharing. Clearance in carrier bearings reduces the bearing load
carrying capacity and thus the bending moment from the rotor can be transmitted into gear meshes. With bearing
clearance, the bending moment can cause tooth micropitting and can induce planet bearing fatigue, leading to
reduced gearbox life. Planet bearings are susceptible to skidding at low input torque.
ISBN: 1-978-61481-036-0 Pages: 16
12FTM06. Virtual Optimization of Epicyclic Gearbox Planet Bearings in Wind Turbines

Authors: S. Vasconi, D. Raju
Demand for higher reliability, robustness and performance in epicyclical gearboxes have led SKF to develop
Design for Six Sigma (DfSS) based simulation tools and methods.
This paper will illustrate the advantages of using simulation driven design in the development of planetary
gearboxes for multi megawatt wind turbines. The simulation example will show the influence of the housing
flexibility and of the non-linear bearing and gear stiffness on the gearbox performance under transient load. In
particular, the load distribution and deformation of the planetary gears and bearings will be analyzed.
The flexibility and accurate stiffness description led to non-intuitive results. The gear deformation and load
distribution led to significantly different results compared to results obtained by using traditional calculation tools
and methods. A comparison between advanced and standard calculation methods is given as evidence that
advanced analyses should be used to design reliable, robust and high performing gearboxes.
A virtual design of experiments was used to determine the most influential parameters affecting the gearbox
performance. This paper will highlight the results of this DfSS study.
ISBN: 1-978-61481-037-7 Pages: 16
12FTM07. Validation of a Model of the NREL Gearbox Reliability Collaborative Wind Turbine Gearbox
Authors: C.K. Halse, Z.H. Wright, A.R. Crowther
Gearboxes in the wind industry have been suffering from a poor reputation due to major issues with reliability.
There has been a long list of issues; e.g. grind temper, material inclusions, axial cracking in bearings, poor load
sharing on shaft-bearing arrangements, significant gear misalignment, bearing ring creep, gear scuffing, gear and
bearing micropitting; all of which are common and often serial problems. There has been improvement in the last
few years for some of the products, yet it is not uncommon for wind sites built as recently as 2008 to have 20–
40% of gearboxes requiring a component replacement (such as a high speed pinion or intermediate shaft bearing)
already (by 2012) and 5–10% complete gearbox failures. An important program for the industry, “The Gearbox
Reliability Collaborative" (GRC), has been funded by the US Department of Energy and run by the National
Renewable Energy Laboratory for several years to aid the industry in improving the reliability of this key
component. The collaborative has brought together manufacturers, academia, national laboratories, engineering
consultants and gear and bearing software providers as part of a program to model, build, simulate and test
gearboxes with a goal to improve reliability and reduce the cost of energy.
The team at NREL have instrumented two gearboxes with over 125 channels, for measurements such as
planetary tooth load distributions, annulus gear hoop strains, planet bearing load distribution, sun orbit and carrier
deflection. They were then subjected to a rigorous testing regime, both up-tower and on the NREL 2.5MW
dynamometer. Romax Technology have been a collaborator in the GRC Analysis Group and have developed
detailed computer simulation models of the gearbox including gear macro and micro-geometry, bearing macro
and micro-geometry, structural stiffness of gearbox housing, carrier and annulus gear, system clearances and
preloads, and surrounding boundary conditions (such as main shaft, rotor hub and bedplate). The model is used
for accurate simulation of the whole system deflections and the prediction of the resulting gear and bearing
contact conditions under various loading conditions.
The focus of this paper is a comparison between measurement and simulation for key parameters including gear
load distributions, annulus deflection and sun motion. The simulation results that are robust and those that are
sensitive to hard-to-predict parameters that include significant effects from manufacturing and assembly variations
will be outlined. Lessons learned in how best to apply computer-aided-engineering tools to improve wind turbine
gearbox reliability will be described.
ISBN: 1-978-61481-038-4 Pages: 12

12FTM08. Combined Marine Propulsion Systems: Optimization and Validation by Simulation
Authors: B. Pinnekamp and F. Hoppe
Modern Navy and Coast Guard Vessels usually have combined propulsion systems using gas turbines, diesel
engines and electric motors as main propulsors. Desired operating profiles demand for individual optimization of
the gear propulsion system with respect to efficiency, noise, operational flexibility and capital cost.
Combined systems are complex and therefore sensitive to dynamic excitation and resonance. To avoid
unfavorable dynamic effects, it is necessary to validate candidate arrangements using modern tools like multi
body simulation.
The paper describes the evaluation process for optimized combined marine propulsion systems and system
validation by dynamic simulation.
ISBN: 1-978-61481-039-1 Pages: 20
12FTM09. Systematic Approach for the Psychoacoustic Analysis of Dynamic Gear Noise Excitation
Authors: C. Brecher, M. Brumm, C. Carl
The sound quality of technical products is an increasingly important quality criterion and has a significant influence
on the product acceptance. But sound quality does not only depend on the physical attributes of the sound signal.
It is defined to a large extent by human sound and noise perception. This perception is based on a physiological
and psychological signal processing. These aspects depend on complex properties of the physical signal like the
spectral distribution and a relative comparison. However, today the sound design of gearboxes is mainly based on
the physical reduction of the noise level that is detected by absolute and objectivized parameters. The noise
oriented gear design is based on a fundament of physical key parameters like the reduction of transmission error
in compliance with achievable manufacturing tolerances. Nevertheless, these design rules may lead to a minimal
sound pressure level but cannot solely be applied for an optimal sound quality in every case. Under economic and
technical aspects there is no excitation free gear set. Furthermore, modern tendencies such as lightweight design
and masking noise reduction (engine downsizing and electrification) lead more and more to scenarios where the
sound of a gear set, which is only designated to have low transmission error, can be perceived as annoying. This
requires design guidelines which take also the human related aspects of gear noise into account. Nowadays the
gear design does not yet consider human noise perception sufficiently.
Thus, a research project at the WZL has been established that investigates the correlation between gear mesh
excitation and the evaluation of gear noise. The objective of this project is to deduce a method for the
consideration of perception-based noise evaluation already in the stage of gear design. Therefore,
psychoacoustics metrics are used to analyze the gear noise of different gear sets in the dimensions of airborne
noise, structural vibration and the excitation due to meshing. The aim of this paper is to discuss the correlation
between the signal properties of the excitation and the radiated noise in order to investigate the possibilities to
transfer the perception related evaluation from sound pressure to the gear mesh excitation. The paper firstly
shows central psychoacoustic parameters that are most relevant for the properties of gear noise. Furthermore, a
new test fixture will be introduced that allows a dynamic measurement of gear mesh excitation directly adjacent to
the meshing. Regarding these aspects two different gear sets are discussed concerning the calculated
transmission error and the experimentally determined excitation, surface vibration and noise radiation. These
aspects are accordingly examined with respect to human noise perception, which is described by
psychoacoustics. It is shown that operating conditions, order distributions as well as the gear geometry are the
main influences on the signal evaluation. The influence of dynamic aspects and especially the influence of
resonance effects on the noise characteristics are additionally considered.
ISBN: 1-978-61481-040-7 Pages: 22
12FTM10. Development of Novel CBN Grade for Electroplated Finish Grinding of Hardened Steel Gears
Authors: U. Sridharan, S. Kompella, S. Ji, J. Fiecoat
The unique requirements of an electroplatable superabrasive CBN grit used in profile grinding of hardened steel
gears as well as the attributes and grinding behavior of a new CBN developed specifically for this application are
discussed. Profile gear grinding parameters were simulated in through-hardened AISI 4140 steel (56 HRC) and
the grinding performance of the new CBN was compared against a competitive CBN grade widely used in the
application. Consistent with field criteria, grinding performance was characterized based on occurrence of 'burn' or
'form' failure. The 'burn' or metallurgical phase transformation failure was detected by Barkhausen Noise Analysis
(BNA) and corroborated by microstructural and microhardness evaluations. The 'form' failure was simulated by
tracking average radial wheel wear to a threshold value where form loss was expected to occur. Grinding tests
indicate that the new CBN grit can grind 35% more parts compared to the competitive CBN grade before burn
failure. In addition, the new CBN displayed a lower wear rate. The new CBN grade also exhibited a unique ability
to grind with lower grinding power, resulting in a near constant BNA response on the ground surface throughout
the test. This implied minimal microstructural change on the ground part from start to end of the test compared to
the progressive softening of ground surface noticed with the competitive CBN.
ISBN: 1-978-61481-041-4 Pages: 13

12FTM11. Contemporary Gear Pre-Machining Solutions
Author: C. Kobialka
Depending on production volumes, batch sizes and work piece geometry, several gear manufacturing
technologies are used for industrial gear production. Most frequently applied is the hobbing process, followed by
broaching, shaping, sintering and rolling processes. Upcoming gear manufacturing processes are power skiving,
forging, precision blanking and cold forging. Due to improvements to the numerical control of direct drive
technology, the power skiving process has become a competitive gear manufacturing process in comparison to
shaping, blanking and broaching. The potential of the reinvented power skiving process will be explained by
production volume analyses, achievable gear quality and gear geometry modifications. Also the economical and
environmentally friendly aspect of the power skiving process will be explained.
ISBN: 1-978-61481-042-1 Pages: 10
12FTM12. Manufacturing Method of Pinion Member of Large-Sized Skew Bevel Gears Using Multi-Axis
Control and Multi-Tasking Machine Tool
Authors: I. Tsuji, K. Kawasaki, H. Gunbara, H. Houjyou, S. Matsumura
In this paper, a manufacturing method of the pinion member of large-sized skew bevel gears using multi-axis
control and multi-tasking machine tool considering that the gear member is provided is proposed. First, the tooth
surface forms of skew bevel gears are modeled. Next, the real tooth surfaces of the gear member are measured
using a coordinate measuring machine and the deviations between the real and theoretical tooth surface forms
are formalized using the measured coordinates. It is possible to analyze the tooth contact pattern of the skew
bevel gears with consideration of the deviations of the real and theoretical tooth surface forms expressing the
deviations as polynomial equations. Moreover, the deviations of the tooth surface form of the gear member are
fed back to the analysis of the tooth contact pattern and transmission errors, and the tooth surface form of the
pinion member that has a good performance mating with the gear member. Finally, the pinion member is
manufactured by swarf cutting using multi-axis control and multi-tasking machine tool. Afterward, the real tooth
surfaces of the manufactured pinion member were measured using a coordinate measuring machine and the
tooth surface form errors were detected. As a result, although the tooth surface form errors were large relatively
on the heel side, those were small on the other side. In addition, the tooth contact pattern of the manufactured
pinion member and provided gear member was compared with those of tooth contact analysis. As a result, there
was good agreement.
ISBN: 1-978-61481-043-8 Pages: 15
12FTM13. Gear Material Selection and Construction for Large Gears

Author: F.C. Uherek
For gears larger than 3 m (10 feet), construction of gear blanks tend to divide into cast steel, ductile iron, and
forged rim welded web structures for use in cylindrical grinding mills and kilns. This paper will review the
application, various options for material selection, and the impact of selection on tooth geometry. A group of
sample gears are developed to compare each of the materials and method of blank construction. Each sample is
discussed in light of structural stress, deflection, expected life, handling weight, material origin, fabrication method,
inspection requirements during construction, and impact of selection on field performance. Based on the above, a
roadmap is developed listing critical considerations and optimal use of each material and method of construction
in this application.
ISBN: 1-978-61481-044-5 Pages: 14
12FTM14. Large Pinions for Open Gears: The Increase of Single Mesh Load – A New Challenge for
Manufacturing and Quality Inspection
Author: M. Pasquier, and F. Wavelet
Most of the large open gear sets for mining industry are designed according to AGMA 6014-A06 and AGMA 2001-
D04. and rating according to AGMA standard (service factor) involve the final design of the pinion such as:
material and heat treatment (through hardening or case carburized pinion), and the finishing process of the teeth
(to achieve the design geometry).
Basically, customer specification and rating according to AGMA standard (service factor) involve the final design
of the pinion such as: material and heat treatment (through hardening or case carburized pinion), and the finishing
process of the teeth (to achieve the design geometry).
Moreover, the increase of applied load for a single meshing becomes a new challenge.
In addition to the mechanical properties for the material used and its associated heat treatment requirements
given in standards, elastic and thermal behavior and resulting accuracy, as well, have to be taken into account at
design stage, even for large open gears.
Beside design consideration, such increase of single meshing load cannot be achieved by using conventional
manufacturing and quality control methods.
Therefore, improvements in manufacturing process and in quality inspections for such heavily loaded single large
parts, as already performed for smaller parts in batch are now mandatory to achieve these new design
requirements.

Based on examples, in this paper, it is presented such manufacturing and the associated quality controls
improvements from steel fabrication to final machining for heavy parts, to ensure the customer that the result
meets the specification requirements.
ISBN: 1-978-61481-045-2 Pages: 20
12FTM15. New Methods for the Calculation of the Load Capacity of Bevel and Hypoid Gears
Authors: C. Wirth, B.-R. Höhn, C. Braykoff
A failure mode called “flank breakage" is increasingly observed in different applications of cylindrical and bevel
gears. These breakages typically start from the active flank approximately in the middle of the active tooth height
and propagate to the tooth root of the unloaded flank side. Crack initiation can be localized below the surface in
the region between case and core of surface hardened gears. This failure mode can neither be explained by the
known mechanism of tooth root breakage nor by the mechanism of pitting. Even bevel gears in truck and bus
applications are at the risk to suffer from subsurface fatigue, if the optimum utilization of the material should be
achieved. In this case a balance between the flank breakage and pitting risk has to be found. The purpose of this
paper is to describe a new material physically based calculation method to evaluate the risk of flank breakage
versus the risk of pitting. The verification of this new method by experimental tests is exemplarily shown.
In cooperation with “ZG-Zahnräer und Getriebe GmbH” (ZG) “MAN truck and bus AG" (MTB) developed a new
method for the calculation of the risks of flank failure by flank breakage and pitting. The calculation method has
been adjusted and approved by experimental tests on powertrain test rigs of MAN. The ten different test gear
variants had an outer diameter of de2 = 390 mm to 465 mm, a ratio i = 4,5 to 5,7 and a normal module of mmn = 6
mm to 8 mm. Also variants with the same main geometry but different Ease-Off designs were examined. All gear
sets were tested under a defined load spectrum. Based on the research work at the FZG (Gear Research Center
at the Technical University of Munich in Germany) of Oster, Hertter and Wirth a calculation method for bevel gears
was established. The principle of the calculation model is the local comparison of the occurring stresses and the
available strength values over the whole tooth volume. Therefore, it is possible to evaluate the risk of initial cracks
beyond the surface of the flank. Close to the surface cracks may grow and cause pitting— especially in the flank
area with negative specific sliding. Cracks in the transient area between case and core lead to a high flank
breakage risk.
First the local stresses and forces on the flank are determined by a loaded tooth contact analysis followed by the
calculation of the maximum exposure (regarding yielding) and dynamic exposure (regarding fatigue) of the
material inside the tooth. Thereby the stress components from the Hertzian contact, bending, thermal effects
(flash temperature) and friction are considered. Furthermore, the positive effect of residual compressive stresses
and accordingly the disadvantageous effect of the residual tensile stresses can be implicated. Finite elements
method investigations have been carried out in order to achieve a sufficient approximation of the residual stress
distribution in the transverse tooth section. The strength values are locally considered, depending on the material
depth and the position on the flank.
The recalculation of the test gears showed a good correlation between the occurred type of damage and the
determined material exposure inside the tooth. The variants failed with flank breakage could be reliably
distinguished from the variants failed by pitting by the new material-physical method. With this knowledge it is now
possible to optimize the main geometry parameters of the gear set (e.g. number of teeth, spiral angle, pressure
angle) as well as the micro geometry (Ease-Off) that influences the load distribution on the flank. Altogether this
new method leads to an insured increase of the permissible material utilization and hence to smaller gear sizes
while keeping the load capacity on a constant level.
ISBN: 1-978-61481-046-9 Pages: 21
12FTM16. Gear Design Optimization for Low Contact Temperature of a High-Speed, Non-Lubricated Spur
Gear Pair
Authors: C.H. Wink, N.S. Mantri
This paper presents a gear design optimization approach that was applied to reduce both tooth contact
temperature and noise excitation of a high-speed spur gear pair running without lubricant. The optimum gear
design search was done using the RMC (Run Many Cases) program from The Ohio State University. Over 480
thousand possible gear designs were considered, which were narrowed down to the 31 best candidates based on
low contact temperature and low transmission error. The best gear design was selected considering, also, its
manufacturability. The selected optimum gear design was compared to an existing gear set using LDP (Load
Distribution Program) from The Ohio State University. Tooth contact temperature was calculated for both designs
using dry a steel-on-steel coefficient of friction. Predicted contact temperature correlated well with results
observed on dynamometer tests with the existing gear set. Predictions with the optimized design showed a 48%
contact temperature reduction and a 79% noise excitation reduction. The low contact temperature of the optimized
design will significantly contribute to preventing tooth surface damage under no lubricant operating conditions.
ISBN: 1-978-61481-047-6 Pages: 9

12FTM17. Dynamic Analysis of a Cycloidal Gearbox Using Finite Element Method
Authors: S. Thube, T. Bobak
Speed reducers incorporating cycloidal technology as their primary reduction mechanism have always been active
topics of research given their unique trochoidal tooth profile. A cycloidal reducer is recognized for its strength and
mainly studied for rotational performance improvement. Nowadays, this study can be performed by digital
prototyping, which has become a valuable tool for simulating exact scenarios without experimenting on actual
model.
This paper discusses the stress distribution, modeled in a dynamic simulation environment, on the rotating parts
of Cycloidal reducer. A three dimensional finite element model is developed using Algor FEA commercial code to
simulate the combined effect of external loading and dynamic as well as inertial forces on one-cycloid disc
system. This model utilizes surface-to-surface contact to define interaction between rotating parts of the reducer
assembly. The results are analyzed for the variation in stress and deformation with respect to time for a certain
simulation period. This study gives an insight of internal load sharing of rotating parts and their capability of
carrying shock loads.
ISBN: 1-978-61481-048-3 Pages: 13
12FTM18. Analysis of Ripple on Noisy Gears

Author: G. Gravel
A low noise level is an important quality feature in modern gearboxes for passenger cars. But a troublesome noise
can have many causes. The noise origination and transmission is amongst others affected by the design layout,
by the actual deviations of the components, by the assembly of the components and also by the mounting
situation of the complete gearbox.
Damages, form errors and displacement errors or ripples are often present on the flanks of a gear, if it is found to
be the cause of problems in a noise check. Especially ripples or 'ghost frequencies' of a gear are problematic,
because up to now they rarely can be detected on a gear measuring device but only in a relative complex single-
flank roll checking procedure.
A new evaluation method now allows to identify and to describe ripples on the flanks of gears based on the results
of a normal gear measurement. The deviation curves were approximated by sine functions, the results are
displayed graphical and by characteristic values. A combination of the deviation of each measured point with its
rotation angle allows an evaluation equal to a rolling with the mating gear. The results show a very good
correlation to a noise check and to a single-flank roll check.
The application of the software is demonstrated by practical examples of the manufacturing methods generating
grinding, honing, broaching and shaving. Vibrations of machine tool and ripple generating influences in the
manufacturing process can be verified down to a level of a few tenth micrometers. At the same time this method is
well suited to describe long-wave form deviations like an ovality or a 3- or 4-fold ripple caused by the clamping or
by a square blank.
With this new evaluation method gears can be tested in an early state of production for known, critical ripples and
conclusions can be drawn on the state of machine tool, cutting tool and clamping device.
ISBN: 1-978-61481-049-0 Pages: 11
12FTM19. A Field Case Study of “Whining" Gear Noise in Diesel Engines

Author: Y. Kotlyar, G.A. Acosta, S. Mleczko, M. Guerra
The proposed paper is a field case study of diesel engine whining gear noise. The paper will describe the
development work performed to reduce the gear whining noise. It will include the problem definition, inspection of
BOB & WOW engines, design of experiment, development and review of gear geometry modifications, inspection
charts, sample size for a statistically significant analysis, and correlation of noise measurement results and tooth
profiles.
ISBN: 1-978-61481-050-6 Pages: 13
12FTM20. The Effect of the Surface Profile on Micropitting

Authors: M. Bell, G. Sroka, R. Benson
A wide choice of surface roughness parameters is available to characterize components, such as gears or
bearings, with the goal of predicting the performance of such metal-to-metal contacting parts. Commonly in
industry, the Roughness Average (Ra) or the Mean Peak-to Valley Height (Rz (DIN)) is chosen to calculate the
Specific Film Thickness Ratio for both superfinished and honed surfaces. However, these two surface roughness
parameters fail to adequately predict the performance properties of surfaces that are superfinished or surfaces
that are honed. In this paper, a superfinished surface is defined as a planarized surface having a ≤0.25 μm Ra. A
honed surface is not considered to be planarized, even with a finish of ≤0.25 μm Ra. Thus, one is falsely led to
predict that a planarized surface or a honed surface, having an equivalent Ra or Rz, will perform similarly. Nothing
is further from the truth. Experimentally, an isotropic planarized surface delivers superior performance. The
following discussion utilizes another roughness parameter, 3s50, to further explain this phenomenon.
ISBN: 1-978-61481-051-3 Pages: 15

12FTM21. Typical Heat Treatment Defects of Gears and Solutions Using FEA Modeling
Authors: Z. Li, B.L. Ferguson
Steel gears are heat treated to obtain enhanced properties and improved service performance. Quench hardening
is one of the most important heat treatment processes used to increase the strength and hardness of steel parts.
Defects seen in quenched parts are often due to high thermal and phase transformation stresses. Typical defects
include excessive distortion, surface decarburization, quench cracks, large grain growth, and unfavorable residual
stresses. Gear geometries with large section differences may suffer high stress concentrations and crack during
quenching. Surface decarburization before quenching may lead to high surface residual tension and possible post
heat treatment cracking. In this paper, the commercial heat treatment software DANTE is used to investigate three
examples of heat treatment defects. Improved processes are suggested with the help of modeling. The first
example is an oil quench process for a large gear. Peeling cracks were observed on the gear surface during
grinding of the quench hardened gears. Computer modeling showed that surface decarburization was the cause.
The second example is a press quench of a large face gear. Unexpected large axial bow distortion was observed
in quenched gears, and computer modeling indicated that an incorrect press load and die setup were the reasons.
The third example is an in-process quenching crack caused by high concentrated tensile stress from unbalanced
temperature and phase transformations in a spiral bevel pinion gear. The quenching process was modified to
solve the problem. This example also emphasizes the need for heat treatment modeling in gear design to reduce
the possibility of heat treatment defects. The three examples illustrate how to effectively use heat treatment
modeling to improve the quality of the gear products.
ISBN: 1-978-61481-052-0 Pages: 14
12FTM22. Crack Testing and Heat Treat Verification of Gears Using Eddy Current Technology
Authors: D. DeVries
While eddy current technology has long been used in the testing of bar, tube, and wire stock, advances in
electronics, automation, and coil design have paved the way for a new generation of testers specifically designed
for component testing applications. This includes the testing of gears and bearings which go into automotive and
industrial applications. These testing systems easily integrate into production processes allowing for in-line testing
at production line speeds. In addition to enabling 100% of production components to be inspected, it can help
monitor upstream processes notifying operators that something is not functioning correctly. This greatly reduces
scrap and warranty costs for gear and bearing manufacturers.
Eddy current crack testing is performed by passing a small pair of coil windings over a section of the component
to be tested. These coil windings are small enough to test between gear teeth, and with multi-coil probes can test
very complex shapes. Most crack test applications require only one test frequency since most tests require the
detection of only surface flaws. Simultaneous testing with multiple frequencies allows for testing of both surface
and sub-surface defects when inspecting nonferromagnetic parts.
While not an absolute hardness test like a Rockwell test, eddy current heat treat verification can achieve sorting
results on par with Rockwell testing. This has been demonstrated with both forged and powder metal gears. Eddy
current heat treat inspection coils come in both standard encircling coil configurations and multi-coil custom
configurations. The custom configurations allow for precise location testing verifying that induction heating
parameters were correctly applied. Defects to be tested include misplaced case, shallow case, short quench,
delayed quench, air cooled, non-heat-treat, and ground out conditions. When performing heat-treat inspection,
multiple test frequencies are used to reliably detect these various heat-treat anomalies.
Eddy current testing offers fast, repeatable testing of gears and bearings. Testing data on each component can be
stored electronically and re-analyzed off-line at a later date. Eddy current test instruments are designed to
integrate with PLC's in material handling stations to set up real-time rejection capabilities. These are all features
that complement modern QC requirements.
ISBN: 1-978-61481-053-7 Pages: 9
12FTM23. Enhancing Control of Distortion Through “One-Piece Flow – Heat Treatment”

Authors: V. Heuer, D. Bolton, K. Löser, T. Leist
Proper control of distortion has become even more important on new powertrain designs. To answer the demand
for fuel-efficient vehicles, modern transmissions are built much lighter, therefore the components of the
transmission exhibit less wall thickness which makes them more sensitive to distortion. Distorted gear
components can create noise in the transmission, require post heat treat machining processes and may even
create problems during transmission assembly.
By applying the technology of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ), the
distortion caused by heat treatment can be significantly reduced. This technology has been successfully
established in serial production for many different gear applications.
With the introduction of One Piece Flow – Heat Treatment, the distortion control can be further enhanced. This
'One-piece Flow – heat treatment' allows for a rapid case hardening where the components are low pressure
carburized at high temperatures (1050°C) followed by gas quenching. The components are not treated in

conventional big batches with multiple layers, but they are treated in small batches consisting of one layer only.
The quench intensity is controlled more precisely to allow for processes which are customized individually for
each gear-component. The single-layer treatment provides
- homogenous and rapid heating of the components;
- homogenous and rapid carburizing of the components;
- homogenous and precisely controlled gas quenching.
All the variations from layer to layer are eliminated, which leads to reductions in distortion-variation within the load.
In addition, this new technology allows strong costs-savings for logistics. The manufacturing-line can be
completely automated since the parts are 1st taken one by one from the soft machining unit, then 2nd heat treated
in time with the cycle-time of soft machining (“Synchronized heat treatment”) and then 3rd passed down one by
one to the hard machining unit. The paper presents applications for enhanced distortion control when using One
Piece Flow – Heat Treatment.”
ISBN: 1-978-61481-054-4 Pages: 14
12FTM24. Recent Inventions and Innovations in Induction Hardening of Gears and Gear-like Components
Author: V. Rudnev
Presentation focuses on recent inventions and innovations (last 4–6 years) in induction hardening of gears and
gear-like components, including but not limited to:
- “Know-how" in controlling distortion of induction hardened gears.
- Simultaneous dual-frequency induction hardening.
- Advanced induction hardening process recipes when hardening small and medium size gears.
- Novel inductor designs to minimize a distortion when induction hardening of hypoid and spiral bevel gears.
- IFP technology for induction gear hardening.
- Induction tempering and stress relieving of gear-like components with improved temperature uniformity.
Presentation also provides a review of basic principles and applications devoted to induction hardening small,
medium and large size gears using tooth-by-tooth techniques and encircling method.
ISBN: 1-978-61481-055-1 Pages: 9
2011 PAPERS
11FTM01. A New Way of Face Gear Manufacturing
There are two major intentions to apply face gears in power transmissions: the advantage to be able to use a
cylindrical gear as a pinion member; and particular design solutions which require a plurality of cylindrical driving
members as in a propulsion system.
While the automotive and truck industry conducted substantial research in the application of face gear systems in
their drive trains, the results did not favor face gears versus bevel and hypoid gears. In many cases, the face gear
system was found to be the less economical solution, as the manufacturing of the face gear itself was expensive.
Machine tools require a special design, are not readily available, and the cutting tools have to be designed
specifically for the particular face gear design.
The obstacles which prevented manufacturers in the past to apply face gears were removed entirely, when a new
way of forming the profile of face gear teeth, using standard bevel gear cutting and grinding machines as well as
standard cutter heads was designed. The idea is based on the tools used in straight bevel gear cutting and
grinding according to the CONIFLEX method, however, using a generating gear which is not flat like it is for
straight bevel gears but cylindrical, resembling the mating cylindrical pinion for the particular face gear design.
The complexity of modified cylindrical hobbing and shaping machines and job dependent custom tooling
disappears completely with the new CONIFACE cutting and grinding process.
ISBN: 1-61481-000-1 Pages: 14
11FTM02. Generating Gear Grinding – New Possibilities in Process Design and Analysis
Authors: J. Reimann, F. Klocke, and C. Gorgels
To improve load carrying capacity and noise behavior, case hardened gears usually are hard finished. One
possible process for the hard finishing of gears is the continuous generating gear grinding, which has replaced
other grinding processes in batch production of small to medium sized gears due to its high process efficiency.
Despite the wide industrial application of this process only a few published scientific analyses exist. The science-
based analysis of generating gear grinding needs a high amount of time and effort. This is due to the complex
contact conditions between tool and gear flank, which change continuously during the grinding process. These
complicate the application of the existing knowledge of other grinding processes onto the generating gear
grinding.

The complex contact conditions lead to high process dynamics which pose challenges in the design of machine
tools, the control engineering and the process design. Furthermore, unfavorable contact conditions can lead to
process related profile form deviation. So the knowledge of the cutting forces and their time dependent behavior is
necessary to describe and optimize the process dynamics and results.
The aim of this report is to determine the existing cutting forces for a sample gear in trials for the first time and to
analyze their connection to the process parameters and the appearance of profile form deviations. Simultaneously
for the sample gear the same process design will be analyzed using a manufacturing simulation. The results of
the trials and the simulation will be compared. The report will present new possibilities in process analysis and will
give the process user ideas for future process improvements.
ISBN: 1-61481-001-8 Pages: 15
11FTM03. Towards an Improved AGMA Accuracy Classification System on Double Flank Composite
Measurements
Author: E. Reiter
AGMA introduced ANSI/AGMA 2015-2-A06 – Accuracy Classification System – Radial System for Cylindrical
Gears – in 2006 as the first major rewrite of the double flank accuracy standard in over twelve years. Although this
document is not yet in wide use, many practical problems exist in the standard which affects its intended benefit.
This document explains the issues related to the use of ANSI/AGMA 2015-2-A06 as an Accuracy Classification
System and recommends a revised system which can be of more service to the gearing industry.
ISBN: 1-61481-002-5 Pages: 14
11FTM04. First International Involute Gear Comparison

Authors: F. Härtig, W. Adeyemi, and K. Knielm
Seven national metrology institutes have carried out the first international intercomparison in the field of gear
metrology organized from the EURAMET (European Association of National Metrology Institutes) with non-
European involvement. As leader the Physikalisch-Technische Bundesanstalt (PTB) provided three of their
involute gear artifacts and sent them to the participants from China, Japan, Thailand, United Kingdom, Ukraine
and USA. Each of the institutes measured the profile, helix and the pitch artifact and evaluated the specified
measurands. The results collected and evaluated by the PTB were compared and analyzed by evaluating the
normalized error En. At the end of this comparison the large distribution of the results which lay in the range of
today's required tolerances in industry pose a lot of questions. The presentation explains details of the
measurement setup and evaluation parameter, damages of some artifacts due to unqualified handling, and finally
the interesting results.
ISBN: 1-61481-003-2 Pages: 11
11FTM05. Epicyclic Load Sharing Map – Application as a Design Tool

Author: A. Singh
One of the main advantages of planetary transmissions is that the input torque is split into a number of parallel
paths. However, equal load sharing between the planets is possible only in the ideal case due to the presence of
positional type manufacturing errors, equal load sharing is not realized, and the degree of inequality in load
sharing has major implications for gear system sizing, tolerancing schemes, and torque ratings.
The sensitivity of load sharing to torque, tolerance level, directionality of error, system flexibility, number of
planets, and amount of float in the system have all been studied. However, a physical understanding of the true
mechanism that leads to the load sharing phenomenon was lacking.
In a recent paper, the author has proposed a physical mechanism that explains all known load sharing behavior.
The physical explanation leads to simple expressions that seem to completely describe the complex load sharing
behavior. Comparisons to computational models and experimental results have shown excellent correlation.
The proposed physical explanation leads to the concept of an epicyclic load sharing map (ELSM). The ELSM is a
plot of the load ratio (or % of input torque) versus a non-dimensional parameter Xe. The non-dimensional
parameter is a function of combined system stiffness, tolerance level, and operating torque. The ELSM contains
curves for 3, 4, 5, 6 and 7 (and more) planet systems. Once a gear set is located on the ELSM, its behavior under
any load and error condition can be quickly predicted. Also, the advantages of adding extra planets can be
accurately estimated.
The use of the ELSM as a design tool for the general case when there are errors on the position of every carrier
pin-hole are illustrated. Statistical simulations are performed for a given manufacturing error distribution for 3 to 7
planet systems
ISBN: 1-61481-004-9 Pages: 25

11FTM06. Reversed Gear Tooth Bending Stress and Life Evaluation
Author: J. Chen
There is a wealth of literature and test results regarding the subject on single directional gear tooth bending stress
and life relationships (S-N curves), they have been published on various journals and handbooks over the past
decades, and several of them had been widely accepted and adapted as industry standards by different gear
societies around the world. However, very limited information regarding the bi-directional tooth bending life has
been revealed.
To fill in the above mentioned gap for practical usages, the authors first intended to apply the traditional fatigue
theories such as modified Goodman, Gerber, Morrow or similar theories with minor modifications to derive a
series of S-N equations for different loading conditions, but the correlation with the actual test results was not
satisfied. Nevertheless, from the observation on these test results, the slopes and endurance limits on the fitted
S-N curves from all the test points were reasonable closer to each other, as long as the test gears were produced
by the same material and similar manufacturing process. Based on the above observation, the author proposes a
new approach that uses the common (or averaged) slope and endurance limit, and a series of S-N curve
equations on any loading conditions can be derived, once the single directional S-N curve has been obtained.
ISBN: 1-61481-005-6 Pages: 19
11FTM07. The Effects of Helix Angle on Root Stresses of Helical Gears

Authors: D.R. Houser and A.P. Thaler
The ISO and AGMA Gear Rating Committees have for several years been comparing the results of different rating
methods for several sets of gear pairs that have similar normal sections but different helix angles. The analysis
presented here uses a finite element code that was developed specifically for gear and bearing contacts to
analyze the example gear sets. Analyses are also performed using a more conventional load distribution analysis
program. The results for the original gear sets show that the narrow face width gear teeth twist significantly, thus
moving the load to one edge of the face width and essentially showing that the example gear sets are highly
unrealistic. Yet when analyzed by the ISO and AGMA rating methods, the results do not reflect this twisting action.
In an effort to come up with a valid comparison of stresses for different helix angles, three adjustments using
wider face widths were attempted. The first uses a narrow load patch in the middle of the tooth pair and results in
the stresses increasing with helix angle. The second scheme again uses a wider face width, but with perfect
involutes. Edge effects result in the peak stresses being near the ends of the face width. The third method, which
uses the wide face width with teeth that have some lead crown and tip relief, gives the most reasonable results,
with the root stresses being at a maximum in the center region of the tooth face widths. The paper compares each
of the results to earlier analyses performed by others using both the AGMA and ISO calculations.
ISBN: 1-61481-006-3 Pages: 14
11FTM08. A Comprehensive System for Predicting Assembly Variation with Potential Application to
Transmission Design
Authors: K.W. Chase and C.D. Sorensen
Recent advances in tolerance analysis of assemblies allow designers to: predict tolerance stack-up due to
process variations; examine variation in clearances and fits critical to performance; use actual production variation
data or estimates from prior experience; and use engineering design limits to predict the percent rejects in
production runs.
A comprehensive system has been developed for modeling 1D, 2D, and 3D assemblies, which includes three
sources of variation: dimensional (lengths and angles), geometric (GD&T), and kinematic (small internal
adjustments due to dimensional variations).
Once the assembly has been described, an algebraic model is created, in which each dimension is represented
by a vector, with a nominal +/- tolerance. The vectors are linked into chains or loops, describing each critical
clearance or assembly feature in terms of the contributing dimensions. The chains form vector loops describing
the interaction and accumulation of the three sources of variation in the assembly.
Small variations are applied to each source and analyzed statistically to predict the resulting variation in the critical
assembly features. Solutions for the mean and standard deviations are obtained by matrix algebra. Only two
assemblies are analyzed: one for the mean and another for the variance of the assembly features. The same
modeling elements may be used to model complex assemblies.
Benefits of tolerance analysis include reduced reject rates, fewer problems on the assembly floor, reduced costs,
and shorter time to market. Critical requirements of shaft alignment, gear meshing and controls in transmissions
and gear trains are ideally suited for this efficient, comprehensive system.
ISBN: 1-978-61481-007-0 Pages: 18

11FTM09. Standardization of Load Distribution Evaluation: Uniform Definition of KHβ for Helical Gears
Author: K. Nazifi
The load distribution measurement of gear teeth and the determination of the face load factor for contact stress
KHβ are of fundamental importance to the gear manufacturing industry. The factor is a measure for the uniformity
of the load along the face width. The closer this factor is to one the more uniform is the load distributed along the
face width. In the design phase this factor is determined with the help of approximation equations and finite
element analysis and is used to dimension the flank modifications. In addition, KHβ is used in the lifetime
calculations according to DIN 3990 and ISO 6336 required by the certification societies. In the testing phase this
factor is experimentally determined by strain measurements of the tooth fillets in order to verify the load
distribution calculations and the suitability of the used modifications.
For spur gears with no helix angle the interpretation of the measurements to a face load factor is intuitively easy.
For helical gears, used more frequently in large gearboxes, the determination of the factor gets more difficult. The
line of contact of these gears runs inclined over the face width of the teeth flank. In this context the question arises
whether the face load factor is evaluated along the face width or along the path of contact.
Evaluation of the measured values and the interpretation to a face load factor is a complex challenge and is not
standardized. The standardization of load distribution evaluation and a uniform definition of KHβ especially for
helical gears enable a safer design for the manufacturers and an easier comparability of the results for the
customers.
The paper will compare the different suggestions to the KHβ definition and will derive a new definition suitable for
the calculation methods in DIN 3990 and ISO 6336.
ISBN: 1-978-61481-008-7 Pages: 18
11FTM10. New Methods for the Calculation of the Load Capacity of Bevel and Hypoid Gears
Authors: B.-R. Höhn, K. Stahl, and C. Wirth
Pitting and tooth root breakage are still the two most frequent failure types occurring in practical applications of
bevel gears. There are several national and international standards for the calculation of the load carrying
capacity of these gears such as DIN 3991, AGMA 2003 and ISO 10300. But up to now these standards do not
cover bevel gears with offset (hypoid gears). For that reason, a research project was carried out at FZG (Gear
Research Centre, Munich, Germany) to analyze the influence of the hypoid offset on the load capacity of bevel
gears by systematic theoretical and experimental investigations.
The results of the tooth root tests showed, as expected, an increasing load capacity with higher offsets. In
contrast, the pitting tests showed an increasing, but after reaching a maximum, a decreasing load capacity with
higher offsets. This can be explained by two interfering phenomena: On the one side higher offsets lead to
decreasing pinion loads and thus decreasing contact stresses; on the other side the permissible stresses are
decreasing due to the higher sliding velocities.
Regarding these test results a new standard capable calculation method was developed on the basis of ISO
10300. First the bevel gear geometry is transformed into a virtual cylindrical gear. Systematic theoretical
investigations and comparisons with tooth contact analysis methods have shown that the new virtual cylindrical
gears have representative mesh conditions compared to the bevel gears. This includes the size and shape of the
contact area as well as the load distribution between the mating teeth. Particularly with regard to hypoids it is
necessary to consider the unbalanced mesh conditions between drive and coast side flank, what can be
described by the limit pressure angle. Several influence factors were adjusted considering geometry, material
properties and operating conditions of the gear set. For the tooth root safety factor, the influence factors were
adapted to the specific conditions of hypoid gears. For the calculation of the pitting safety factor two new influence
factors were introduced to consider the hypoid specific sliding conditions on the gear flanks. The recalculation of
the pitting and tooth root tests showed a very good correlation of calculated with real load capacity of the test
gears.
Meanwhile the newly developed calculation method is widely-used in the gear manufacturing industry. For that
reason, it is currently introduced into the revision of ISO 10300 as method B1 beside method B2 based on the
AGMA calculation method for bevel and hypoid gears.
ISBN: 1-978-61481-009-4 Pages: 20
11FTM11. Marine Reversing Main Gear Rating Factor Versus Number of Loading Reversals and Shrink
Fit Stress
Authors: E.W. Jones, S. Ismonov and S.R. Daniewicz
The marine vessel reversing main gear tooth is subjected to three different loading cycles: ahead travel with load
pulsing from zero to 100% of full power; astern travel with load pulsing from zero to about minus 66% of full
power; and reversal of direction with load changing from 100% of full power to about minus 66% of full power.

The number of repetitions of these three different loading cycles varies with the vessel duty cycle and life. The
published values of allowable design stress for teeth are based on pulsing loads, which must be modified for this
third loading cycle. The tooth may also be subjected to mean stress due to shrink fitting of the gear onto a hub.
Publications which address these conditions include:
- Guide values for mean stress influence factor, Ym, of ISO 6336-3 gives a factor, which de-rates the pulsing,
i.e. unidirectional, allowable stress value for non-pulsing load.
- The American Bureau of Shipping Rules, derate the allowable unidirectional bending strength by 10% for the
reversing main gear tooth. (Idler gear teeth, which are under bidirectional loading at full power, are de-rated
by 30%).
- Det Norske Veritas DNV Classification Notes No. 41.2 addresses gears: with other working conditions than
pure pulsations; with periodical changes of rotational direction; and with shrink fitting stresses. For gears
with occasional full load in reversed direction such as the main wheel in a reversing gearbox, the derating
factor of 10% is recommended.
This paper evaluates the derating factor for marine reversing main gear tooth allowable bending stress using the
Goodman fatigue line and Miners equation as a function of the average number of changes in vessel direction per
hour, shrink fitting stress values, and different materials based on the AGMA values for allowable stress and life
factor.
ISBN: 1-978-61481-010-0 Pages: 18
11FTM12. The Application of the First International Calculation Method for Micropitting
Authors: U. Kissling
The international calculation method for micropitting, ISO/TR 15144, was recently published. It is the first official
international calculation method to check for the risk of micropitting ever published. Years ago AGMA published a
method for the calculation of the specific oil film thickness containing some comments about micropitting, and the
German FVA published a calculation method based on intensive research results. The FVA and the AGMA are
close to the ISO/TR. New is the calculation of the micropitting safety factors.
The technical report presents two calculation rules, method A and B. Method A needs as input the Hertzian
pressure on every point of the tooth flank, based on an accurate calculation of the meshing of the gear pair,
considering tooth and shaft deflections to get the load distribution over the flank line in every meshing position.
Method B is much simpler; the load distribution is defined for different cases as spur or helical gears, with and
without profile modifications.
The risk of micropitting is highly influenced by profile and flank line modifications. A new software tool can
evaluate the risk of micropitting for gears by automatically varying different combinations of tip reliefs, other profile
modifications and flank line modifications, in combination with different torque levels, using method A. The user
can define the number of steps for variation of the amount of modification. Then all possible combinations are
checked combined with different (user defined) torque levels. Any modifications including flank twist, arc-like
profile modifications, etc. can be combined. The result is presented in a table, showing the safety factor against
micropitting for different subsets of profile/flank modifications, depending on the torque level.
Some applications from wind turbine and industrial gearboxes, known to the author, will be discussed.
ISBN: 1-978-61481-011-7 Pages: 15
11FTM13. Investigations on the Flank Load Carrying Capacity in the Newly Developed FZG Back-to-Back Test
Rig for Internal Gears
Authors: B.-R. Höhn, K. Stahl, J. Schudy, T. Tobie, and B. Zornek
Micropitting, pitting and wear are typical gear failure modes, which can occur on the flanks of slowly operated and
highly stressed internal gears. However, the calculation methods for the flank load carrying capacity have mainly
been established on the basis of experimental investigations on external gears.
The target of a research project was to verify the application of these calculation models to internal gears.
Therefore, two identical back-to-back test rigs for internal gears have been designed, constructed and
successfully used for gear running tests. These gear test rigs are especially designed for low and medium
circumferential speeds and allow the testing of the flank load carrying capacity of spur and helical internal gears
for different pairings of materials at realistic stresses. The three planet gears of the test rig are arranged uniformly
around the circumference. Experimental and theoretical investigations regarding the load distribution across the
face width, the contact pattern and the load sharing between the three planet gears have been carried out.
Furthermore, substantial theoretical investigations on the characteristics of internal gears were performed. Internal
and external spur gears were compared regarding their geometrical and kinematical differences as well as their
impact on the flank load. Based on the results of these theoretical investigations an extensive test program of load
stage tests and speed stage tests on internal gears of different material, different finishing of the flanks and
different operating conditions has been carried out. The main focus of this test program was on the fatigue failures
of micropitting and wear at low circumferential speeds.

The paper describes the design and functionality of the new developed test rigs for internal gears and shows
basic results of the theoretical studies. Furthermore, it presents basic examples of experimental test results.
ISBN: 1-978-61481-012-4 Pages: 16
11FTM14. AGMA 925-A03 Predicted Scuffing Risk to Spur and Helical Gears in Commercial Vehicle
Transmissions
Author: C.H. Wink
The risk of gear tooth scuffing in commercial vehicle transmissions has gained more attention because of
increasing demand for fuel-efficient powertrain systems in which diesel engines run at lower speeds, power
density is higher, and lubricants are modified to improve efficiency and compatibility with components of new
technologies, such as dual clutch transmissions. Thus, predicting scuffing risk during the design phase is vital for
the development of commercial vehicle transmissions. AGMA 925-A03 is a comprehensive method to predict the
probability of gear scuffing. Therefore, this paper presents the AGMA 925-A03 scuffing risk predictions for a series
of spur and helical gear sets in transmissions that are used in commercial vehicles ranging from SAE class 3
through class 8. Limiting scuffing temperatures of mineral and synthetic lubricants were determined from FZG
scuffing tests, dynamometer tests and field data. The agreement between prediction, test results and actual usage
can provide confidence in the predictor of scuffing risk of gears in commercial vehicle transmissions.
ISBN: 1-978-61481-013-1 Pages: 11
11FTM15. Micropitting – A Serious Damage? Testing, Standards and Practical Experience

Authors: B. Pinnekamp, T. Weiss and G. Steinberger
Micropitting is a surface fatigue phenomenon on highly loaded case hardened gear flanks. Main contributors are
local stress, surface roughness, sliding speed and lube oil properties. To determine the lube oil performance with
respect to micropitting, different test methods have been established in the past. Actual proposals are evaluated
for adopting suitable calculation methods for micropitting resistance to the ISO 6336 gear rating standards. But is
micropitting necessarily a damage in any case? Practical experience shows, that a certain level of micropitting is
actually acceptable, leading to even more favorable load distribution and can end up in a stable flank condition
performing without problems for the designed service live.
The paper describes testing, calculation approaches and application to practical cases with respect to micropitting
on wind turbine and high speed gears and perennial observations and experience.
ISBN: 1-978-61481-014-8 Pages: 15
11FTM16. Gear Lubrication – Stopping Micropitting by Using the Right Lubricant

Authors: M. Hochmann and H. Siebert
Micropitting is a type of fatigue failure occurring on hardened tooth flanks of highly loaded gears. This failure
consists of very small cracks and pores on the surface of tooth flanks. Micropitting looks greyish and causes
material loss and a change in the profile form of the tooth flanks, which can lead to pitting and breakdown of
the gears.
The formation of micropitting depends on different influences. Besides material, surface roughness, and geometry
of the tooth flanks, the lubricant and the operating conditions show a main influence on micropitting formation.
The micropitting load-carrying capacity of gears can be calculated according to ISO/TR 15144-1, where the
influence of lubricant, operating conditions, and surface roughness is considered with the specific lubricant film
thickness. For this purpose, the specific lubricant film thickness of a practical gear is compared with a minimum
required specific lubricant film thickness. The latter is the specific film thickness where no micropitting risk is given
for a lubricant and can be determined by performing a micropitting test according to FVA 54/7. This test procedure
consists of a load stage test and an endurance test. Lubricants with a high micropitting load-carrying capacity
reach the failure criterion of a profile form deviation of 7.5 µm due to micropitting in load stage greater than or
equal to LS 10 of the load stage test. In the endurance test, a stagnation of micropitting formation compared with
the micropitting area at the end of the load stage test is preferred but not required.
In field applications, micropitting formation is often reported even though industrial gear oils with a high
micropitting load-carrying capacity are used. Such oils offer a good micropitting protection determined in the load
stage test, but with a low micropitting performance in the endurance test.
The aim of research is therefore the investigation whether a change from an oil with low micropitting performance
in the endurance test to an oil with high micropitting performance in the endurance test can stop the micropitting
formation.
ISBN: 1-978-61481-015-5 Pages: 11
11FTM17. Morphology of Micropitting

Author: R.L. Errichello
Micropitting occurs in gears and rolling-element bearings that operate in the mixed or micro EHL lubrication
regime. It manifests in many different ways depending on the loads, speeds, rolling and sliding velocities,

macrogeometry, surface topography, edge effects, metallurgy, and lubricant properties. The failure analyst must
discern whether the micropitting is a primary failure mode or a secondary failure that occurs because of prior
damage. Understanding the morphology of micropitting is the key to determining the primary failure mode and root
cause of failure.
Several examples of micropitting in gears and rolling-element bearings are presented to illustrate the
morphological variation that can occur in practice.
ISBN: 1-978-61481-016-2 Pages: 19
11FTM18. Longitudinal Tooth Contact Pattern Shift

Authors: J.B. Amendola, J.B. Amendola III, and D. Yatzook
After a period of operation turbo gears may exhibit a change in the tooth contact pattern, reducing full face width
contact, and thereby increasing the risk of tooth distress due to the decreased loaded area of the teeth.
The phenomena may or may not occur. In some units the shift is more severe than others and has been observed
in cases where there is as little as 50,000 hours of operation. In other cases, there is no evidence of any change
for units in operation for more than 100,000 hours. This condition has been observed primarily in single helical
gears with low helix angles (10–13°). All recorded observations have been with case carburized hardened and
ground gear sets.
This paper describes the phenomena observed among some of many installed high speed gear units in field
operation that have been inspected. The authors have not found any written material describing this behavior and
upon further investigation suggest a possible cause. Left unchecked and without corrective action, this occurrence
may result in tooth breakage.
ISBN: 1-978-61481-017-9 Pages: 11
11FTM19. Convoloid® Gearing Technology – The Shape of the Future

Authors: B.E. Berlinger, Jr. and J. Colbourne
Since the invention of the involute curve and the application thereof to gearing, the world has embraced and
developed this type of gear tooth form to a very high degree of engineering and manufacturing excellence.
Improvements in recent years have been relatively modest, since this form has been so rigorously studied and
applied. The long term adoption of the involute is rooted in large part to the simplicity of its tools and field
operation. Straight sided tools and conjugacy, even with limited changes in center distance, were consistent with
the industrial revolution of the 18th, 19th, and 20th centuries, and the mechanically based machine tools of these
ages. The recent ubiquitous nature of computers and CNC machinery exacerbates the cost effective freedom to
optimize many parameters affecting gear tooth forms.
Convoloid is a new gear tooth form capable of increasing torques 20% to 35% over those of conventionally
designed involute pairs. The form is computer optimized, is compatible with the world's existing capital asset
infrastructure, and mirrors the manufacturing sequences, processes and basic production costs of involute gears.
The result is a major enhancement in gear drive system power density and cost reduction for a given power
requirement. Convoloid gearing is totally scalable and is used in parallel axis helical, planetary, and other
configurations.
The design, rating (surface durability and bending), flash temperature analysis and other important performance
criteria for this technology along with the manufacturing and inspection protocols in keeping with AGMA and ISO
specifications will be discussed. Test results confirming many of the superior load carrying characteristics of this
tooth form will be presented. Side by side comparisons of involute versus Convoloid designs and test performance
results will be presented confirming the validity of the theory.
ISBN: 1-978-61481-018-6 Pages: 18
11FTM20. Case Study Involving Surface Durability and Improved Surface Finish
Authors: G. Blake and J. Reynolds
Gear tooth wear and micro-pitting is a very difficult phenomenon to predict analytically. The failure mode of micro-
pitting is closely correlated to the lambda ratio. Micropitting can be the limiting design parameter for long-term
durability. Also, the failure mode of micropitting can progress to wear or macropitting, and then manifest into more
severe failure modes such as bending. The results of a gearbox test and manufacturing process development
program will be presented to evaluate super finishing and its impact on micropitting.
Testing was designed using an existing aerospace two stage gearbox with a low lambda ratio. All gears were
carburized, ground and shot peened. Two populations were then created and tested. One population was finish
honed and the second was shot peened and isotropic super finished.
A standard qualification test was conducted for 150hrs at maximum continuous load. The honed gears
experienced micro and macro pitting during the test. The Isotropic Super Finishing (ISF) gears were also tested
for 150hr under the same loading. The ISF gears were absent of any surface distress. The ISF gears were further

subjected to a 2000hr endurance test. The ISF gears had less surface distress after 2000hr than the baseline
honed gears after 150hrs.
ISBN: 1-978-61481-019-3 Pages: 18
11FTM21. Gearbox Bearing Service Life – A Matter of Mastering Many Design Parameters
Author: H. Wendeberg
The service life of a gearbox is determined by many factors. The bearings in the gearbox play a major role since
they themselves deliver an important function, and in addition interact with the shafts, the casing and the oil.
Without a doubt, the sizing of the bearings is of great importance for the gearbox reliability. Since more than 50
years the bearing dynamic carrying capacity has been used to determine a suitable size needed to deliver a
sufficient fatigue life – but despite the advanced calculation methods developed, the methods do not fully predict
service life. Producers of high quality bearings have introduced high performance class bearings and, lacking
better ways to express the improved performance, this is only represented by increased dynamic carrying
capacity.
The availability of high-strength shaft materials in combination with bearings with high carrying capacity allows
slimmer shafts to be used. The modulus of elasticity remains the same, so seat design for bearings and gears
must be given close attention.
This paper covers the following: sizing of bearings based on dynamic carrying capacity and how this relates to
service life; how the design of the interface between bearing and shafts should be adapted to modern shaft
materials; how the design of the interface between bearing and gearbox casing influences service life of the
gearbox; and influence of modern electric motor speed controls in bearing type selection.
ISBN: 1-978-61481-020-9 Pages: 17
11FTM22. Bearing Contribution to Gearbox Efficiency and Thermal Rating: How Bearing Design Can Improve
the Performance of a Gearbox
Author: A. Doyer
Gearbox efficiency is a topic of rising interest amongst both OEM and end-users due to an increased sensitivity to
gearbox performance, reliability, total cost of ownership (energy cost), overall impact on the environment, and also
anticipating future regulations.
In a gearbox there are difference sources of losses: gear, lubrication, seal and bearing loss. The use of modern
simulation tools makes easier the evaluation of losses in various load case conditions. It has been demonstrated
that the contribution of bearing loss on the system efficiency is dependent on the load cases. Even if the bearing
is by far not the primary source of losses, the optimization of the bearing set can significantly improve gearbox
performance. Simulation of a single stage gearbox using tapered roller bearings shows that the running
temperature of the gearbox can be reduced up to 10C, by using latest bearing generation. Such a saving could
improve the thermal rating of the gearbox by up to 30%. Experiments also demonstrated that different design of
tapered roller bearing shows significant variation in friction performance.
Having proper bearing design can significantly improve the performance of a gear unit: by a lower running
temperature, by improving lubricant life, potentially simplified lubrication system, and consequently reduced
running cost.
ISBN: 1-978-61481-022-3 Pages: 12
11FTM23. Integration of Case Hardening into the Manufacturing-Line: “One Piece Flow”
Authors: V. Heuer, K. Löser, G. Schmitt and K. Ritter
For decades the gear industry has addressed the challenge to produce high performance components in a cost-
efficient manner. To meet quality specifications, the components need to be heat treated, which traditionally takes
place in a central hardening shop. However, this separation between machining and heat treatment results in high
costs for transportation and logistics within the production plant. Therefore, for many years it has been being
discussed how to integrate heat treatment into the manufacturing line.
For about 10 years it has been possible to integrate heat treatment into the machining facility by applying the
technology of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ). The components are
collected after soft-machining into big batches and treated with LPC- and HPGQ-technology. This means however
that the heat treatment is not synchronized with soft- and hard-machining since the components must be collected
in buffers before heat treatment and must be singularized again after heat treatment.
In order to totally integrate heat treatment into the manufacturing line and in order to synchronize heat-treatment
with machining, a new heat treatment cell has been developed. Following the philosophy of “One Piece Flow” the
parts are: taken one by one from the soft machining unit; then heat treated in time with the cycle-time of soft
machining (“synchronized heat treatment”) and then passed down one-by-one to the hard machining unit. To
allow for rapid case hardening, the components are low pressure carburized at high temperatures (1050°C)
followed by gas quenching.

In addition to the cost-savings for logistics, the new concept in equipment offers the following advantages:
individual processes customized for each gear-component; homogenous and quick heating of the components
and therefore low spread of distortion; homogenous and controllable gas quenching and therefore low spread of
distortion; environmentally friendly carburizing and quenching; and compact and space-saving heat treat unit.
The paper shows first results achieved with the new process technology applied in the new heat treatment cell.
ISBN: 1-978-61481-023-0 Pages: 12
11FTM24. Induction Hardening of Gears with Superior Quality and Flexibility Using Simultaneous Dual
Frequency (SDF®)
Authors: C. Krause, F. Biasutti, and M. Davis
Induction hardening of gear teeth is well known for its challenges, but also for its potential for improved quality and
process control. For complex geometric parts like gears, the power density and induction frequency need to be
adjusted very precisely to achieve the required hardening pattern. Since 1940s it is known that working with two
simultaneous frequencies (1–15 kHz and 200–20 000 kHz) is the optimal way to heat a geared part to hardening
temperature. The key point in this process is that the medium frequency (about 10 kHz) affects primarily the tooth
root and the high frequency affects first of all the tip of the tooth and the flanks. The right combination of the power
densities of medium- and high-frequency energy values and the heating time are the crucial factors to reach a
contour true heating pattern and, thereby, a contour true hardening pattern.
The authors will describe the state of the art of induction hardening of gears with simultaneous dual frequency
using some examples of use and present the possibilities to manipulate the hardening pattern in a positive way for
different gear geometries.
ISBN: 1-978-61481-024-7 Pages: 8
11FTM25. Controlling Gear Distortion and Residual Stresses During Induction Hardening
Authors: Z. Li and B.L. Ferguson
Induction hardening is widely used in both automotive and aerospace gear industries to reduce distortion and
obtain favorable residual stresses. The heating process during induction hardening has a significant effect on the
quality of the heat-treated parts, but the importance of the quench portion of the process often receives less
attention. However, experiences have shown that the cooling rate, cooling fixture design and cooling duration can
significantly affect the quality of the hardened parts in terms of distortion, residual stresses, as well as the
possibility of cracking. DANTE is commercial heat treatment software based on finite element method. In this
paper, DANTE is used to study an induction hardening process for a helical ring gear made of AISI 5130 steel.
Prior to induction hardening, the helical gear is gas carburized and cooled at a controlled cooling rate. In this
study, two induction frequencies in sequential order are used to heat the gear tooth. After induction heating, the
gear is spray quenched using a polymer/water solution. By designing the spray nozzle configuration to quench the
gear surfaces with different cooling rates, the distortion and residual stresses of the gear can be controlled. The
crown and unwind distortions of the gear tooth are predicted and compared for different quenching process
designs. The study also demonstrates the importance of the spray duration on the distortion and residual stresses
of the quenched gear.
ISBN: 1-978-61481-025-4 Pages: 12
11FTM26. Atmosphere Furnace Heating Systems

Author: J.W. Gottschalk
A detailed evaluation of furnace heating systems is presented. Topics of discussion include application guidelines
for both gas fired and electrically heated furnaces. Heating system selection considers operating temperature,
processing atmosphere and heating method (radiant or convective heating) along with heating system orientation
within the furnace chamber.
The evaluation consists of a comparison of operating costs, environmental considerations and lifetime
maintenance costs of the various systems. Systems to be evaluated consist of alloy radiant tubes (single ended,
U-tube, etc.), ceramic radiant tubes (single ended and U-tubes) and a variety of electrical element designs. Actual
case studies of the various heating systems are presented with respect to maintenance and operating costs.
ISBN: 1-978-61481-026-1 Pages: 8
11FTM27. Manufacturing and Processing of a New Class of Vacuum-Carburized Gear Steels with Very
High Hardenability
Authors: C.P. Kern, J.A. Wright, J.T. Sebastian, J.L. Grabowski, D.F. Jordan and T.M. Jones
Ferrium C61 and C64 are new secondary-hardening steels that provide superior mechanical properties versus
9310, 8620, Pyrowear Alloy 53 and other steels typically used for power transmission, such as significantly higher
core tensile strength, fracture toughness, fatigue strength and thermal stability (i.e. tempering temperature). One
recent example of their application is the application of C61 to the forward rotor shaft of CH-47 Chinook helicopter,
in order to reduce the weight of the shaft by 15–25% and provide other benefits.

This paper reviews the significant manufacturing and processing benefits that arise from this new class of
secondary-hardening steels, and analyze the potential implications and opportunities. C61 and C64 were
computationally designed to take advantage of high-temperature, low-pressure (i.e. vacuum) carburization
technology, in part by combining carburizing and austenizing steps as well as being designed to have very high
hardenability. The very high hardenability of these steels permits a mild gas quench subsequent to low-pressure
vacuum carburizing and reduces part distortion, thus reducing grind stock removal, simplifying final machining and
heat treat operations. A framework analysis is used to compare total manufacturing/production costs and impacts
(including environmental) of these new steels versus traditional gear steels. Conclusions and recommendations
are drawn regarding best manufacturing practices and appropriate use of these new steels for product
applications.
ISBN: 1-978-61481-027-8 Pages: 14
11FTM28. Simulation of Wear for High Contact Ratio Gear – A Mixed FE and Analytical Approach
Authors: G. Venkatesan, M. Rameshkumar and P. Sivakumar
High contact ratio gears offer high load carrying capacity and increased life with less volume and weight. Gear
tooth wear of high contact ratio gears is of great importance as excessive wear is characterized by loss of tooth
profile and thickness, which might result in higher dynamic gear mesh and tooth forces. Surface wear changes not
only the contact pattern and load distribution, but also the vibration and noise characteristics of the gear system.
This paper deals with the simulation of wear for high contact ratio (HCR) and normal contact ratio (NCR) gears
using a Mixed Finite Element (FE) and analytical approach. A numerical model for wear prediction of gear pair is
developed. The methodology employs single point, observation-based gear contact mechanics in conjunction with
the Archard's wear formulation to predict the tooth wear in spur gears. The contact pressure and loads are
determined using a FE approach in which a two dimensional deformable body contact model of HCR and NCR
gears is analyzed in ANSYS software, and ANSYS Parametric Design language (APDL) is used for capturing the
load sharing ratio and contact stress variation on the complete mesh cycle of the gear pair. A MATLAB code
program is developed to determine the sliding velocities, equivalent contact radius and contact width along the
path of contact for both HCR and NCR gears. The contact loads and pressures obtained using FEM are used for
predicting the wear depth for NCR and HCR gear pair.
ISBN: 1-978-61481-021-6 Pages: 12
2010 PAPERS
10FTM01. Complete Machining of Gear Blank and Gear Teeth
Author: C. Kobialka
Demands for increased throughput, with smaller lot sizes at lower cost have led to the development of an
innovative approach to machining both: the gear bland and gear teeth on a single machine.
This paper will concentrate on the potentials and risks of combined process machines what are capable of turning,
hobbing, drilling, milling, chamfering and deburring of cylindrical gears. The same machine concept can be used
for singular operations of each manufacturing technology on the same design concept. This leads to reduced
amounts of different spare parts, increases achievable work piece quality and harmonizes on common user
friendliness. In the end the economic potential of combined process technology and a vision for integrated heat
treatment is shown.
ISBN: 1-55589-976-9 Pages: 8
10FTM02. Improving Heat Treating Flexibility for Wind Turbine Gear Systems through Carburizing,
Quenching and Material Handling Alternatives
Author: W. Titus
Part handling and processes for heat treating large gears have created challenges for decades. Growth in wind
energy technology has focused more attention on this issue in recent years. The vast majority of installations
processing such large parts utilize conventional methods via pit furnace systems. Such equipment has inherent
limitations with respect to quench flow and part handling, making true improvements in areas such as distortion
control difficult due to physical limitations of this processing approach. This presentation will explain alternative
methods for heat treating large components that allow part distortion to be minimized. Benefits will be quantified
regarding cost savings to produce such gearing and quality.
ISBN: 1-55589-977-6 Pages: 19
10FTM03. A Novel Approach to the Refurbishment of Wind Turbine Gears

Authors: M. Michaud, G.J. Sroka and R.E. Benson
Multi-megawatt wind turbine gearboxes operate under demanding environmental conditions including
considerable variation in temperature, wind speed, and air quality. It is not uncommon for gearboxes rated for a
maintenance free 20-year lifespan to fail after only a few years. These gearboxes experience several types of
repairable damage including micropitting or “gray staining", abrasive wear, foreign object debris (FOD) damage,
surface corrosion and fretting corrosion. Wear is greatest on the input stage, especially on the sun pinion gear.
Historically, grinding is utilized to refurbish these damaged gears. However, there are numerous drawbacks

including but not limited to high capital investment and the extraordinary amount of time and skill involved in the
grinding process. Moreover, nitrided gears cannot be ground and must be scrapped. However, chemically
accelerated vibratory finishing, or isotropic superfinishing (ISF), represents a value adding, low-cost option for
refurbishing both case carburized and nitrided gears. Isotropic superfinishing removes light to moderate gear flank
surface damage. The result is a surface with a non-directional pattern with a roughness of approximately 0.08 mm
or less. Moreover, evidence suggests that isotropic superfinishing imparts a finish that increases gear durability
and service life in the field. A case study on a sun pinion gear is presented.
ISBN: 1-55589-978-3 Pages: 10
10FTM04. Low Distortion Heat Treatment of Transmission Components

Authors: V. Heuer, K. Löser, D.R. Faron and D. Bolton
In many applications the high demands regarding service life of transmission components can be reached only by
the application of a customized case hardening. This case hardening process results in a wear resistant surface-
layer in combination with a tough core of the component. However, as a side-effect the components get distorted
during heat treatment. This distortion has a significant cost-impact, because distorted components often need to
be hard-machined after heat treatment. Therefore, the proper control of distortion is an important measure to
minimize production costs.
By applying the technology of low pressure carburizing (LPC) and high pressure gas quenching (HPGQ) heat
treat distortion can be significantly reduced. HPGQ provides a very uniform heat transfer coefficient. The
predictability of movement during quenching is more certain and uniform throughout the load. Further
improvements can be achieved by “Dynamic Quenching" processes where the quenching severity is varied during
the quench sequence by step control of the gas velocity. Proper fixturing is another factor for distortion control.
Modern CFC-materials (carbon reinforced carbon) are well suited as fixture-material for gas quenching.
The paper presents how LPC and HPGQ processes are successfully applied on internal ring gears for a 6 speed
automatic transmission. The specific challenge in the heat treat process was to reduce distortion in such a way
that subsequent machining operations are entirely eliminated. As a result of extensive development in the
quenching process and the use of specialized CFC-fixtures it was possible to meet the design metrological
requirements.
The Internal ring gears addressed in this report have been in continuous production since 2006. Subsequent
testing and monitoring over a two-year period progressively demonstrated that consistent metrology was achieved
and quality inspection was reduced accordingly.
ISBN: 1-55589-979-0 Pages: 16
10FTM05. Comparison of the AGMA and FEA Calculations of Gears and Gearbox Components Applied in the
Environment of Small Gear Company
Author: V. Kirov
The current AGMA standards provide a lot of information about the calculations of loose gears and gearbox
components – shafts, splines, keys, etc. These recommendations are based mostly on the “traditional" methods of
mechanical engineering, found in many classical textbooks and research papers. Their accuracy and reliability
have been proven in many years of gearbox design and field tests. They are clear, concise, in most cases easy to
program and apply even by a small gear company with limited resources. However new methods for calculations
of mechanical engineering components like FEA (finite element analysis) are becoming wide spread. Once these
techniques were used only by big companies because of their complexity and price but with the development of
the computer technology they become more and more accessible to small gear companies which are the majority
of participants in the market.
Nowadays, in the gear business, even a small gear company is usually in possession of a modern CAD system
which always includes a basic or advanced FEA package. Such CAD systems are most often run by one gear
engineer who makes 3D models, engineering calculations and production drawings. The level of the FEA
packages is such that it allows the gear engineer to be able to do components calculations without deep
knowledge in the FEA itself.
So the question about the effectiveness of the traditional AGMA calculations and the new FEA methods becomes
of vital importance particularly for small firms.
ISBN: 1-55589-980-6 Pages: 9
10FTM06. Finite Element Analysis of High Contact Ratio Gear

Authors: M. Rameshkumar, G. Venkatesan and P. Sivakumar
Modern day vehicles demand higher load carrying capacity with less installed volume and weight. The gears used
in the vehicles should also have lesser noise and vibration. Even though helical gears will meet the requirement,
they are prone for additional axial thrust problem. High contact ratio (HCR) is one such gearing concept used for
achieving high load carrying capacity with less volume and weight. Contact ratio greater than 2.0 in HCR gearing
results in lower bending and contact stresses. Previously published literature deal with studies on various
parameters affecting performance of HCR gears but a comparison of HCR and normal contact ratio (NCR) gears
with same module and center distance has not been carried out so for. This paper deals with finite element

analysis of HCR, NCR gears with same module, center distance and the comparison of bending, contact stress
for both HCR, NCR gears. A two dimensional deformable body contact model of HCR and NCR gears is analyzed
in ANSYS software. ANSYS Parametric Design language (APDL) is used for studying the bending and contact
stress variation on complete mesh cycle of the gear pair for identical load conditions. The study involves design,
modeling, meshing and post processing of HCR and NCR gears using single window modeling concept to avoid
contact convergence and related numerical problems.
ISBN: 1-55589-981-3 Pages: 12
10FTM07. A New Statistical Model for Predicting Tooth Engagement and Load Sharing in Involute Splines
Authors: J. Silvers, C.D. Sorensen and K.W. Chase
Load-sharing among the teeth of involute splines is little understood. Designers typically assume only a fraction of
the teeth are engaged and distribute the load uniformly over the assumed number of engaged teeth. This
procedure can widely over- or underestimate tooth loads.
A new statistical model for involute spline tooth engagement has been developed and presented earlier, which
takes into account the random variation of gear manufacturing processes. It predicts the number of teeth engaged
and percent of load carried by each tooth pair. Tooth-to-tooth variations cause the clearance between each pair of
mating teeth to vary randomly, resulting in a sequential, rather than simultaneous tooth engagement. The
sequence begins with the tooth pair with the smallest clearance and proceeds to pick up additional teeth as the
load is increased to the maximum applied load. The new model can predict the number of teeth in contact and the
load share for each at any load increment.
This report presents an extension of the new sequential engagement model, which more completely predicts the
variations in the engagement sequence for a set of spline assemblies. A statistical distribution is derived for each
tooth in the sequence, along with its mean, standard deviation and skewness. Innovative techniques for
determining the resulting statistical distributions are described. The results of an in-depth study are also
presented, which verify the new statistical model. Monte Carlo Simulation of spline assemblies with random errors
was performed and the results compared to the closed-form solution. Extremely close agreement was found. The
new approach shows promise for providing keener insights into the performance of spline couplings and will serve
as an effective tool in the design of power transmission systems.
ISBN: 1-55589-982-0 Pages: 17
10FTM08. Calculation of Load Distribution in Planetary Gears for an Effective Gear Design Process
Authors: T. Schulze, C. Hartmann-Gerlach, B. Schlecht
The design of gears—especially planetary gears—can just be carried out by the consideration of influences of the
whole drive train and the analysis of all relevant machine elements. In this case the gear is more than the sum of
its machine elements. Relevant interactions need to be considered under real conditions. The standardized
calculations are decisive for the safe dimensioning of the machine elements with the consideration of realistic load
assumptions. But they need to be completed by extended analysis of load distribution, flank pressure, root stress,
transmission error and contact temperature.
ISBN: 1-55589-983-7 Pages: 11
10FTM09. Reverse Engineering

As America's manufacturing base has contracted the need for reverse engineering has grown. Well established
suppliers have disappeared, often leaving customers with no source of spare parts or technical support. Over time
certain pieces of equipment require changes to output speeds or power levels and new parts have to be designed,
built, and installed. And unfortunately, some pieces of equipment don't measure up to the demands they are
subjected to and need redesign or improvement. In many ways, reverse engineering is just as demanding a
discipline as original product development with many of the same challenges but plus the additional restrictions of
fitting inside of an existing envelope.
The typical reverse engineering project begins with very limited information on the existing piece of equipment.
This paper will describe a methodology for the reliable measurement, evaluation, re-design, and manufacture of
replacement parts for gearboxes and industrial machinery. A step-by-step example will be provided.
ISBN: 1-55589-984-4 Pages: 9
10FTM10. Evaluation of Methods for Calculating Effects of Tip Relief on Transmission Error, Noise and
Stress in Loaded Spur Gears
Author: D. Palmer and M. Fish
The connection between transmission error and noise and vibration during operation has long been established.
Calculation methods have developed to describe the influence such that it is possible to evaluate the relative
effect of applying a specific modification at the design stage. The calculations can allow the designer to minimize
the excitation from the gear pair engagement at a specific load. This paper explains the theory behind
transmission error and the reasoning behind the method of applying the modifications through mapping the
surface profiles and deducing the load sharing. It can be used to explain the results of later experimental

validation on various types of tip relief in low contact ratio (LCR) gears, from very long to very short. The paper will
also demonstrate that though the effects of modification in any specific case can be modeled with some certainty,
the same modifying strategy cannot be applied universally but must consider the required operating conditions. It
illustrates that the effect of tip relief on transmission error and load sharing is not a black art but can be fully
explained by applying existing theory.
A study of high contact ratio (HCR) gears will be presented to demonstrate why it is often necessary to apply
different amounts and extents of tip relief in such designs, and how these modifications affect load sharing and
highest point of tooth loading. Specific attention will be paid to the phenomenon of extended contact, where if no
modification or insufficient tip relief is applied, contact does not stop at the end of active profile but continues
beyond this point as the gear rotates resulting in contact on the tip. This effectively increases contact ratio and has
implications for the tooth load and in particular how this may affect the loading position, highest point of single
tooth contact (HPSTC), which is relevant to both ISO and AGMA standard rating. The paper will consider 3
methods commonly employed in the industry; a simple 2D mapping procedure carried out on graph paper, a 3D
linear tooth stiffness computation method, and a 3D finite element analysis (FEA) calculation. The paper will
demonstrate that though in some cases these methods can produce similar results, albeit with varying degrees of
accuracy, further examples will be presented which demonstrate behavior which can only be detected using some
of the more complex analysis methods. The commercial viability of implementing a better quality models against
the time constraints in the development process will be discussed and conclusions drawn.
ISBN: 1-55589-985-1 Pages: 15
10FTM11. Point-Surface-Origin, PSO, Macropitting Caused by Geometric Stress Concentration, GSC

Authors: R.L. Errichello, C. Hewette, and R. Eckert
Point-Surface-Origin, PSO, macropitting occurs at sites of Geometric Stress Concentration, GSC, such as
discontinuities in the gear tooth profile caused by micropitting, cusps at the intersection of the involute profile and
the trochoidal root fillet, and at edges of prior tooth damage such as tip-to-root interference. When the profile
modifications in the form of tip relief, root relief, or both are inadequate to compensate for deflection of the gear
mesh, tip-to-root interference occurs. The interference can occur at either end of the path of contact, but the
damage is usually more severe near the start-of-active-profile, SAP, of the driving gear.
An FZG-C gearset (with no profile modifications) was tested at load stage 9 and three pinion teeth failed by PSO
macropitting. It is shown that the root cause of the PSO macropitting was GSC created by tip-to-root interference.
ISBN: 1-55589-986-8 Pages: 11
10FTM12. Flank Load Carrying Capacity and Power Loss Reduction by Minimized Lubrication
Authors: B.-R. Höhn, K. Michaelis and H.-P. Otto
The lubrication of gears has two major functions: Reducing friction and wear as well as dissipating heat. The
power losses, especially the no-load losses, decrease with decreasing immersion depth using dip lubrication. The
load-dependent gear power losses are nearly unaffected by minimized lubrication. However, the gear bulk
temperatures rise dramatically by using minimized lubrication due to a lack of heat dissipation.
With minimized lubrication the scuffing load carrying capacity decreased by up to more than60%compared to rich
lubrication conditions. The dominating influence of the bulk temperature is therefore very clear. Starved lubrication
leads to more frequent metal-to-metal contact and the generation of high local flash temperatures must be
considered. An additional factor for the scuffing load carrying capacity calculation in case of minimized lubrication
conditions is proposed.
Concerning pitting damage test runs showed that by lowering the oil level the load cycles without pitting damage
decreased by approximately 50% up to 75% for minimized lubrication compared to the results with rich lubrication
conditions. The allowable contact stress is clearly reduced (up to 30%) by minimized lubrication. A reduced oil film
thickness as a consequence of increased bulk temperatures results in more frequent metal-to-metal contacts
causing a higher surface shear stress. In combination with a decreased material strength due to a possible
tempering effect at high bulk temperatures the failure risk of pitting damage is clearly increased. The common
pitting load carrying capacity calculation algorithms according to DIN/ISO are only valid for moderate oil
temperatures and rich lubrication conditions. For increased thermal conditions, the reduction of the pitting
endurance level at increased gear bulk temperatures can be approximated with the method of Knauer (FZG TU
München, 1988). An advanced calculation algorithm for pitting load carrying capacity calculation at high gear bulk
temperatures (valid for high oil temperatures as well as for minimized lubrication) is proposed.
The micropitting risk was increased by low oil levels, especially at high loads and during the endurance test. The
micropitting damage is caused by poor lubrication conditions which are characterized by a too low relative oil film
thickness due to high bulk temperatures. Again, the actual bulk temperatures are of major significance for
calculation of the micropitting load carrying capacity.
The wear rate of the gears is almost unaffected by the oil level. Only a slight increase of wear could be observed
with minimized lubrication. This increase can be explained by the higher bulk temperature of the gears running

under minimized lubrication conditions. The investigations showed that there exists a natural limitation for lowering
the oil quantity in transmissions without detrimental influence on the load carrying capacity. Knowing these
limitations enables the user to determine the possible potential benefits of reduced oil lubrication. The correct
prediction of the actual gear bulk temperatures is of major importance in this context. A method for the estimation
of the gear bulk temperature at reduced immersion depth respectively poor lubrication conditions is proposed.
ISBN: 1-55589-987-5 Pages: 15
10FTM13. Gear Design for Wind Turbine Gearboxes to Avoid Tonal Noise According to ISO/IEC 61400-11
Author: J. Litzba
Present wind turbine gearbox design usually includes one or two planetary gear stages and at least one high
speed helical gear stage, which play an important role regarding noise and vibration behavior. Next to the overall
noise of the gearbox and the structure-born noise on the gearbox housing also tonal noise is becoming a much
more important issue in recent years. Since tonal noise is problematic due to the human perception as
“uncomfortable", avoidance is important. Conventional theories regarding low noise gear design are not
developed in view of tonal noise. This leads to the question: How to deal with tonal noise in the design stage and
which gear parameters can be used for an optimization regarding good tonal noise behavior?
Within a research project measurements have been performed on different gearboxes using different gear
designs. These measurements have been evaluated according to ISO/IEC 61400-11 and the results have been
analyzed in view of the influence of different gear parameters. It was also investigated if it is possible to rank
gearboxes in wind turbines according to their tonal noise behavior as observed on the test rig.
The paper will give an introduction into the definition of tonal noise according to ISO/IEC 61400-11 and give
insight in measurement results from test rigs and from gearboxes in the field, where noise behavior is also
evaluated according to ISO/IEC 61400-11. Furthermore, the paper will show and discuss the link between
measurement results and different gear parameters, which are affecting tonal noise behavior. In addition,
simulation results will be presented, showing how tonal noise can be estimated within the design stage using
state-of-the–art calculation software.
The paper will give recommendations regarding a gear design process that is considering tonal noise in the
design stage and will compare an, regarding tonal noise, improved gear set with an older one.
ISBN: 1-55589-988-2 Pages: 19
10FTM14. Analysis and Testing of Gears with Asymmetric Involute Tooth Form and Optimized Fillet Form for
Potential Application in Helicopter Main Drives
Authors: F.W. Brown, S.R. Davidson, D.B. Hanes, D.J. Weires and A. Kapelevich
Gears with an asymmetric involute gear tooth form were analyzed to determine their bending and contact stresses
relative to symmetric involute gear tooth designs which are representative of helicopter main drive gears.
Asymmetric and baseline (symmetric) toothed gear test specimens were designed, fabricated and tested to
experimentally determine their single-tooth bending fatigue strength and scuffing resistance. Also, gears with an
analytically optimized root fillet form were tested to determine their single-tooth bending fatigue characteristics
relative to baseline specimens with a circular root fillet form. Test results demonstrated higher bending fatigue
strength for both the asymmetric tooth form and optimized fillet form compared to baseline designs. Scuffing
resistance was significantly increased for the asymmetric tooth form compared to a conventional symmetric
involute tooth design.
ISBN: 1-55589-989-9 Pages: 15
10FTM15. Drive Line Analysis for Tooth Contact Optimization of High Power Spiral Bevel Gears
Authors: J. Rontu, G. Szanti and E. Mäsä
It is a common practice in high power gear design to apply relieves to tooth flanks. They are meant to prevent
stress concentration near the tooth edges. Gears with crownings have point contact without load. When load is
applied, instantaneous contact turns from point into a Hertzian contact ellipse. The contact area grows and
changes location as load increases. To prevent edge contact, gear designer has to choose suitable relieves
considering contact indentations as well as relative displacements of gear members. In the majority of spiral bevel
gears spherical crownings are used. The contact pattern is set to the center of active tooth flank and the extent of
crownings is determined by experience. Feedback from service, as well as from full torque bench tests of
complete gear drives have shown that this conventional design practice leads to loaded contact patterns, which
are rarely optimal in location and extent. Too large relieves lead to small contact area and increased stresses and
noise; whereas too small relieves result in a too sensitive tooth contact.
Today it is possible to use calculative methods to predict the relative displacements of gears under operating load
and conditions. Displacements and deformations originating from shafts, bearings and housing are considered.
Shafts are modeled based on beam theory. Bearings are modeled as 5-DOF supports with non-linear stiffness in
all directions. Housing deformations are determined by FEM-analysis and taken into account as translations and

rotations of bearing outer rings. The effect of temperature differences, bearing preload and clearances are also
incorporated.
With the help of loaded tooth contact analysis (LTCA), it is possible to compensate for these displacements and
determine a special initial contact position that will lead to well centered full torque contact utilizing a reasonably
large portion of the available tooth flank area. At the same time, crownings can be scaled to the minimum
necessary amount. This systematic approach leads to minimum tooth stressing, lower noise excitation as well as
increased reliability and/or power density as compared to conventional contact design method.
During recent years ATA Gears Ltd. has gained comprehensive know-how and experience in such analyses and
advanced contact pattern optimization. The methodology and calculation models have been verified in numerous
customer projects and case studies.
ISBN: 1-55589-990-5 Pages: 14
10FTM16. Analysis of Load Distribution in Planet-Gear Bearings

Authors: L. Mignot, L. Bonnard and V. Abousleiman
In epicyclic gear sets aimed at aeronautical applications, planet-gears are generally supported by spherical roller
bearings with bearing outer race being integral to the gear hub. This paper presents a new method to compute
roller load distribution in such bearings where the outer ring can't be considered rigid. Based on well-known Harris
method, a modified formulation enables to account for centrifugal effects due to planet-carrier rotation and to
assess roller loads at any position throughout the rotation cycle. New model load distribution predictions show
discrepancies with results presented by Harris, but are well correlated with 1D and 3D Finite Element Models.
Several results validate the use of simplified analytical models to assess the roller load distribution instead of
more time consuming Finite Element Models. The effects of centrifugal effects due to planet-carrier rotation on
roller loads are also analyzed. Finally, the impact of the positions of rollers relative to the gear mesh forces on the
load distribution is shown.
ISBN: 1-55589-991-2 Pages: 11
10FTM17. Self-Locking Gears: Design and Potential Applications

Authors: A.L. Kapelevich and E. Taye
In most of the gear drives, when the driving torque is suddenly reduced as a result of power off, torsional vibration,
power outage or any mechanical failure at the transmission input side, then gears will be rotating either in the
same direction driven by the system inertia, or in the opposite direction driven by the resistant output load due to
gravity, spring load, etc. The latter condition is known as backdriving. During inertial motion or backdriving, the
driven output shaft (load) becomes the driving one and the driving input shaft (load) becomes the driven one.
There are many gear drive applications where the output shaft driving is less desirable. In order to prevent it,
different types of brake or clutch devices are used. However, there are also solutions in gear transmission that
prevent inertial motion or backdriving using self-locking gears without any additional devices. The most common
one is a worm gear with a low lead angle. In self-locking worm gears, torque applied from the load side (worm
gear) is blocked, i.e. cannot drive the worm. However, their application comes with some limitations: the crossed
axis shafts' arrangement, relatively high gear ratio, low speed, low gear mesh efficiency, increased heat
generation, etc.
The paper describes the design approach as well as potential applications of the parallel axis self-locking gears.
These gears, unlike the worm gears don't have such application limitations. They can utilize any gear ratio from
1:1 and higher. They can be external, internal, or incorporated into the planetary gear stage or multistage gear
system. Their gear mesh efficiency is significantly higher than the worm gears and closer to conventional gears.
As a result, they generate less heat. The self-locking can be designed to prevent either the inertia driving, or
backdriving, or both. The paper explains the principle of the self-locking process for gears with symmetric and
asymmetric teeth profile, and shows their suitability for different applications. It defines the main parameters of
gear geometry and operating conditions. It also describes potential self-locking gear applications and references
to related publications.
ISBN: 1-55589-992-9 Pages: 8

2009 PAPERS
09FTM01. Influence of the Residual Stresses Induced by Hard Finishing Processes on the Running
Behavior of Gears
Authors: V. Vasiliou, C. Gorgels and F. Klocke
Low noise and high load carrying capacity are two important characteristics of competitive power transmissions.
The challenge in the development, design and manufacturing of these power transmissions is to meet these
requirements economically. One of the ways to meet both of these requirements is through a process known as
hard finishing. There are various types of hard finishing and it is important to know which process produces which
requirement.
The aim of this research project is to induce residual stresses in the edge of the work pieces by different hard
finishing processes and to analyze their influence on the durability of the gears. The tested gears are
manufactured by profile grinding, gear honing and generating grinding. The gear deviations and the finish quality
have to be comparable. Through this the influence of the residual stresses on the durability can be analyzed
independent from the geometrical conditions. The presentation will show the results of the load carrying capacity
tests depending on the values of the residual stresses.
ISBN: 1-55589-954-7 Pages: 11
09FTM02. Implementing ISO 18653, Evaluation of Instruments for the Measurement of Gears
Authors: R.C. Frazer and S.J. Wilson
A trial test of the calibration procedures outlined in ISO 18653, Gears – Evaluation of instruments for the
measurement of individual gears, showed that the results are reasonable, but a minor change to the uncertainty
formula is recommended.
Gear measuring machine calibration methods are reviewed. The benefits from using work-piece like artifacts are
discussed and a procedure for implementing the standard in the work place is presented.
Problems with applying the standard to large gear measuring machines are considered and some
recommendations are offered.
ISBN: 1-55589-955-2 Pages: 15
09FTM03. Producing Profile and Lead Modifications in Threaded Wheel and Profile Grinding
Author: A. Türich
Modern gear boxes are characterized by high torque load demands, low running noise, and compact design. In
order to fulfill these demands, profile and lead modifications are being applied more and more. The main reason
for the application of profile and or lead modification is to compensate for the deformation of the teeth due to load,
thus ensuring proper meshing of the teeth which will result in optimized tooth contact pattern.
This paper will focus on how to produce profile and lead modifications by using the two most common grinding
processes, threaded wheel and profile grinding. In addition, more difficult modifications, such as defined flank twist
or topological flank corrections, will also be described in this paper.
ISBN: 1-55589-956-1 Pages: 16
09FTM04. New Developments in Gear Hobbing

Author: O. Winkel
Several innovations have been introduced to the gear manufacturing industry in the past few years. In the case of
gear hobbing, dry cutting technology and the ability to do it with powder-metallurgical HSS-materials might be two
of the most impressive ones. But the technology is still moving forward. The aim of this paper is to present recent
developments in the field of gear hobbing, focusing on innovations regarding tool materials, process technology
and process integration.
ISBN: 1-55589-957-8 Pages: 18
09FTM05. HYPOLOID™ Gears with Small Shaft Angles and Zero to Large Offsets
Author: H. Stadtfeld
Beveloid gears are used to accommodate a small shaft angle. The manufacturing technology used for beveloid
gearing is a special set up of cylindrical gear cutting and grinding machines.
A new development, called Hypoloid gearing, addresses the desire of gear manufacturers for more freedom in
shaft angles. Hypoloid gear sets can realize shaft angles between zero and 20� and at the same time allow a
second shaft angle (or an offset) in space which provides the freedom to connect two points in space.
In all wheel-driven vehicles that traditionally use a transfer case with a pinion/idler/gear arrangement or a chain,
the exit of the transfer case needs to be connected with the front axle. This connection necessitates the use of two
CV joints, because the front axle input point has a vertical offset and is shifted sideways with respect to the
transfer case exit. Compared to a single CV joint, the two CV connections are more costly and less efficient.

However, the newly developed Hypoloids can remedy the situation by offering more freedom in shaft angle and
additional offset which eliminates the need for an additional CV joint. Moreover, the Hypoloid technology offers
enhanced performance compared to beveloids with straight teeth. In addition to the automotive drive trains,
Hypoloid technology can be applied to aircraft as well as general gearbox manufacturing.
ISBN: 1-55589-958-5 Pages: 15
09FTM06. Dependency of the Peak-to-Peak Transmission Error on the Type of Profile Correction and
Transverse Contact Ratio of the Gear Pair
Author: U. Kissling
Profile corrections on gears are a commonly used method to reduce transmission error, contact shock, and
scoring risk. There are different types of profile corrections. It is a known fact, that the type of profile correction
used will have a strong influence on the resulting transmission error. The degree of this influence may be
determined by calculating tooth loading during mesh. The current method for this calculation is very complicated
and time consuming; however, a new approach has been developed which could reduce the calculation time.
This approach uses an algorithm which includes the conventional method for calculating tooth stiffness in regards
to bending and shearing deformation, flattening due to Hertzian pressure, and tilting of the tooth in the gear body.
The new method was tested by comparing its results with FEM and LVR.
This paper illustrates and discusses the results of this study. Furthermore, the maximum local power losses are
compared with the scoring safety calculated following the flash temperature criteria of AGMA 925 and DIN 3990.
ISBN: 1-55589-959-2 Pages: 19
09FTM07. Optimizing Gear Geometry for Minimum Transmission Error, Mesh Friction Losses and
Scuffing Risk
Authors: R.C. Frazer, B.A. Shaw, D. Palmer and M. Fish
Minimizing gear mesh friction losses is important if plant operating costs and environmental impact are to be
minimized. This paper describes how a validated 3D FEA and TCA can be used to optimize cylindrical gears for
low friction losses without compromising noise and power density. Some case studies are presented and generic
procedures for minimizing losses are proposed. Future development and further validation work is discussed.
ISBN: 1-55589-960-8 Pages: 20
09FTM08. Load Sharing Analysis of High Contact Ratio Spur Gears in Military Tracked Vehicle Application
Authors: M. Rameshkumar, P. Sivakumar, K. Gopinath and S. Sundaresh
Military tracked vehicles demand a very compact transmission to meet mobility requirements. Some of the
desirable characteristics of these transmissions include: increased rating, improved power to weight ratio, low
operating noise and vibration, and reduced weight. To achieve all or some of these characteristics, it is has been
decided to apply a High Contact Ratio (HCR) spur gearing concept which will improve load carrying capacity,
lower vibration, and reduce noise. Similar to helical gears, the load in HCR gearing is shared by minimum two pair
of teeth. Therefore, load sharing analysis was conducted on Normal Contact Ratio (NCR) gearing used in sun-
planet gears of an existing drive.
This paper deals with analysis of load sharing of individual teeth in mesh for different load conditions throughout
the profile for both sun and planet gears of NCR/HCR gearing using Finite Element Analysis. Also, the paper
reveals the variation of bending stress and deflection along the profile of both gearing designs.
ISBN: 1-55589-961-5 Pages: 12
09FTM09. Designing for Static and Dynamic Loading of a Gear Reducer Housing with FEA
Authors: M. Davis, Y. S. Mohammed, A.A. Elmustafa, P.F. Martin and C. Ritinski
A recent trend has been toward more user friendly products in the mechanical power transmission industry. One
of these products is a high horsepower, right angle, shaft mounted drive designed to minimize installation efforts.
Commonly referred to as “alignment-free” type, this drive assembly offers quick installation with minimum level of
expertise required. It is also more cost effective. These characteristics make this type of drive ideal for use in
applications such as underground mining where there is little room to maneuver parts.
An alignment free drive is direct coupled to the driven shaft only; it is not firmly attached to a foundation or rigid
structure. A connecting link or torque arm connects the drive to a fixed structure, which limits the drive's rotational
movement about the driven shaft. The electric motor is supported by the reducer housing through a fabricated
steel motor adapter; the coupling connecting the motor shaft and reducer shaft is enclosed by this motor adapter.
FEA was used to test the cast iron housing to determine any potential problem areas before production began.
Once analyses were completed, the motor adaptor was redesigned to lower stresses using the information from
the FEA and comparing it to the infield test data.
ISBN: 1-55589-962-2 Pages: 9

09FTM10. The Effect of Flexible Components on the Durability, Whine, Rattle and Efficiency of a
Transmission Geartrain System
Author: A. Korde and B.K. Wilson
Gear Engineers have long recognized the importance of considering system factors when analyzing a single pair
of gears in mesh. These factors include: load sharing in multi-mesh gear trains, bearing clearances, and effects of
flexible components such as housings, gear blanks, shafts, and carriers for planetary gears. Quality requirements
and expectations in terms of durability, lower operating noise and vibration, and efficiency have increased. With
increased complexity and quality requirements, a gear engineer must use advanced system design tools to
ensure a robust gear train is delivered on time, meeting all quality, cost, and weight requirements.
As a standard practice, finite element models have traditionally been used for analyzing transmission system
deflections, but this modeling environment does not always include provisions for analysis of vibration, efficiency,
or any considerations for attribute variation. And that often requires many runs of the test to ensure all variations
have been included and tested.
An advanced software tool is available for the analysis of transmission system durability, noise, vibration, and
efficiency, all within a single programming environment, including the effects of flexible components such as
housings, gear blanks, and shafting, while also allowing manufacturing variation studies to be performed. This
paper includes the results of a case study of this program.
ISBN: 1-55589-963-9 Pages: 13
09FTM11. Unique Design Constraints for Molded Plastic Transmissions

Authors: R. Kleiss and E. Wiita
Molded plastic gears and transmissions must work effectively in extremely variable conditions just as their
counterparts in steel. Plastics have the added variables of large thermal expansion and contraction, moisture
absorption, greater tolerance variation, lower strength, and form deviations due to the molding process. The
design of a molded transmission must consider these effects and characteristics. This paper will offer an example
of the development of a molded plastic gear pump intended for the very steady delivery of 50 psi water pressure
for a medical application. It will present our approach in design, tolerancing, material selection, molding
procedure, and testing to achieve and verify an effective as-molded transmission.
ISBN: 1-55589-964-6 Pages: 7
09FTM12. The Anatomy of a Micropitting Induced Tooth Fracture Failure – Causation, Initiation, Progression
and Prevention
Authors: R.J. Drago, R.J. Cunningham, and S. Cymbala
Micropitting has become a major concern in certain classes of industrial gear applications, especially wind power
and other relatively highly loaded somewhat slow speed applications, where carburized gears are used to
facilitate maximum load capacity in a compact package. While by itself the appearance of micropitting does not
generally cause much perturbation in the overall operation of a gear system, the ultimate consequences of a
micropitting failure can, and frequently are, much more catastrophic.
Micropitting is most often associated with parallel axis gears (spur and helical) however, the authors have also
found this type of distress when evaluating damage to carburized, hardened and hard finished spiral bevel gears.
This paper presents a discussion of the initiation, propagation and ultimate tooth fracture failure mechanism
associated with a micropitting failure. The subject is presented by way of the discussion of detailed destructive
metallurgical evaluations of several example micropitting failures that the authors have analyzed on both parallel
axis and bevel gears.
ISBN: 1-55589-965-3 Pages: 12
09FTM13. Bending Fatigue, Impact Strength and Pitting Resistance of Ausformed Powder Metal Gears
Authors: N. Sonti, S. Rao and G. Anderson
Powder metal (P/M) process is making inroads in automotive transmission applications because of substantially
lower cost of P/M steel components for high volume production as compared to wrought or forged steel parts.
Although P/M gears are increasingly used in powered hand tools, gear pumps, and as accessory components in
automotive transmissions, P/M steel gears are currently in limited use in vehicle transmission applications.
The primary objective of this project was to develop high strength P/M steel gears with bending fatigue, impact,
and pitting fatigue performance equivalent to current wrought steel gears. Ausform finishing tools and process
were developed and applied to powder forged (P/F) steel gears in order to enhance the strength and durability
characteristics of P/M gears, while maintaining the substantive cost advantage for vehicle transmission
applications.
This paper presents the processing techniques used to produce Ausform finished P/F steel gears, and
comparative bending fatigue, impact and surface durability performance characteristics of Ausform finished P/F
steel gears, as well as conventional wrought steel gears.
ISBN: 1-55589-966-0 Pages: 14

09FTM14. Design Development and Application of New High-Performance Gear Steels
Authors: J.A. Wright, J.T. Sebastian, C.P. Kern, and R.J. Kooy,
A new class of high strength, secondary hardening gear steels that are optimized for high-temperature, low-
pressure (i.e., vacuum) carburization is being developed. These alloys were computationally designed as
secondary-hardening steels at three different levels of case hardness. The exceptional case hardness, in
combination with high core-strength and toughness properties, offer the potential to reduce drive train weight or
increase power density relative to incumbent alloys such as AISI 9310 or Pyrowear® X53.
This new class of alloys utilizes an efficient nano-scale M2C carbide strengthening dispersion, and their key
benefits include: high fatigue resistance (contact, bending, scoring); high hardenability achieved via low-pressure
carburization (thus reducing quench distortion and associated manufacturing steps); a tempering temperature of
>900�F to provide up to a 500�F increase in thermal stability relative to incumbent alloys; and core tensile
strengths in excess of 200 ksi. Ferrium C69™ is one alloy in this family that can achieve a carburized surface
hardness of HRC 67 (with a microstructure substantially free of primary carbides), has exceptionally high contact
fatigue resistance which make it an excellent candidate for applications such as camshafts and bearings as well
as gear sets.
ISBN: 1-55589-967-7 Pages: 14
09FTM15. High Performance Industrial Gear Lubricants for Optimal Reliability

Authors: K.G. McKenna, J. Carey, N.Y. Leon, and A.S. Galiano-Roth
In recent years, gearbox technology has advanced and Original Equipment Manufacturers have required gear oils
to meet the lubrication requirements of these new designs. Modern gearboxes operate under severe conditions
and maintain their reliability to ensure end-user productivity. The latest generation of industrial gear lubricants can
provide enhanced performance even under extreme operating conditions for optimal reliability and reduced cost of
operation.
This paper describes how gear lubricants function in gearboxes and discusses the facts vs. myths of industrial
gear lubricants. The paper will show how advanced gear lubricant technology can optimize the life of the gears,
bearings and seals, resulting in reduced cost of operation. Opportunities to use advanced synthetic gear
lubricants to achieve operational benefits in the areas of improved energy efficiency, wider operating temperature
ranges, extended oil drain intervals and equipment life will be discussed.
ISBN: 1-55589-968-4 Pages: 16
09FTM16. Allowable Contact Stresses of Jacking Gear Units Used in the Offshore Industry
Author: A. Montestruc
An offshore jack-up drilling rig is a barge upon which a drilling platform is placed. The barge has legs which can
be lowered to the sea floor to support the rig. Then the barge can be “jacked-up” out of the water providing a
stable work platform from which to drill for oil and gas. The rack and pinion systems used to raise and lower the
rig are enormous in terms of gear pitch or module by gear industry standards. Quarter pitch (101.6 module)
pinions are common. Lifetime number of cycles for these units are—again, by gear industry standards—small, as
rack teeth typically have 25-year lifetime cycles measured in the low hundreds. That is off the charts for AGMA
(and ISO or DIN) design rules which draw a straight line to zero cycles for contact stress cycles less than 10,000.
Use of any standards was abandoned from the start in the offshore industry for jacking applications. The author
presents methods, and experience of that industry and suggested allowable contact stresses in such applications.
ISBN: 1-55589-969-1 Pages: 8
09FTM17. Variation Analysis of Tooth Engagement and Load-Sharing in Involute Splines

Authors: K. Chase, C. Sorenson and B. DeCaires
Involute spline couplings are used to transmit torque from a shaft to a gear hub or other rotating component.
External gear teeth on the shaft engage an equal number of internal teeth in the hub. Because multiple teeth
engage simultaneously, they can transmit much larger torques than a simple key and keyway assembly. However,
due to manufacturing variations, the clearance between each pair of mating teeth varies, resulting in only partial
engagement.
A new model for tooth engagement, based on statistics, predicts that the teeth engage in a sequence, determined
by the individual clearances. As the shaft load is applied, the tooth pair with the smallest clearance engages first
then deflects as the load increases, until the second pair engages. Thus, only a subset of teeth carry the load. In
addition, the load is non-uniformly distributed, with the first tooth carrying the biggest share. As a consequence,
the load capacity of spline couplings is greatly reduced, though still greater than a single keyway.
This paper discusses the results of a statistical model which predicts the average number of teeth which will
engage for a specified load, plus or minus the expected variation. The model quantitatively predicts the load and
stress in each engaged pair. Critical factors in the model are the stiffness and deflection of a single tooth pair and
the characterization of the clearance. Detailed finite element analyses were conducted to verify the tooth

deflections and engagement sequence. The closed form statistical results were verified with intensive Monte Carlo
simulations.
ISBN: 1-55589-970-7 Pages: 14
09FTM18. Does the Type of Gear Action Affect the Appearance of Micro-Pitting and Gear Life?
Authors: A. Williston
Early results from testing conducted have raised questions concerning the role of gear action with the appearance
of micropitting as well as surface fatigue (macropitting). Comparisons between similar gear sets with the same
loads, speeds, and lubrication but operated either as speed increasers or as speed reducers have yielded
strikingly different propensities for wear. Further, these observations are not limited to lubrication based failures
such as micropitting, but, so far, have applied to traditional surface fatigue failures (macropitting) as well.
Findings point to an increase in the presence of micropitting on gearing operated as speed reducers. All
components are operating at the same speed and load, yet wear is greatly reduced for the driven components.
Perhaps more intriguing is that to date all macropitting failures have occurred to the driving pinions of gear sets
operated as speed reducers. While the number of samples is decidedly small, the length of life for these
components is much less than would be anticipated under smooth load circumstances. The other gear sets
(operated as speed increasers) do not show any fatigue wear.
In addition to how gear action affects micropitting in gearing is the question of how the gear action affects fatigue
life. Current gear rating standards are based upon statistical analysis of real-world experience and mathematical
stress-versus-cycle calculations. If gear action affects how gearing fails in fatigue, there may be significant
ramifications in the industry. However, before any such conclusion may be made, additional testing is necessary.
ISBN: 1-55589-971-4 Pages: 30
09FTM19. The Effect of Gearbox Architecture on Wind Turbine Enclosure Size

Gearbox architecture—the type of gearing used, the overall gear ratio, the number of increaser stages, the
number of meshes, the ratio combinations, and the gear proportions—can have a profound effect on the
“package” size of a wind turbine. In this paper the author applies a common set of requirements to a variety of
potential gearbox designs for a 2.0 MW wind turbine and compares the resulting “geared component” weights,
gearbox envelope sizes, generator sizes, and generator weights. Each design option is also evaluated for
manufacturing difficulty via a relative cost estimate.
ISBN: 1-55589-972-1 Pages: 19
2008 PAPERS
08FTM01. Parametric Study of the Failure of Plastic Gears
Authors: M. Cassata and Dr. M. Morris
This paper presents the results of collaboration to develop tools for the prediction of plastic gear tooth failure for
any given set of operating conditions and to classify failure modes of these gears. The goal of the project is to
characterize and predict the failure of plastic gears over a range of given parameters.
A test plan was developed to explore the effect of rotational speed, root stress, and flank temperature on the life of
plastic gears. The dependent variable for the experiments was the number of cycles (or rotations) until failure.
ISBN: 1-55589-931-8 Pages: 7
08FTM02. A Methodology for Identifying Defective Cycloidal Reduction Components Using Vibration
Analysis and Techniques
Authors: V. Cochran and T. Bobak
For several years, predictive maintenance has been gaining popularity as method for preventing costly and time
consuming machine breakdowns. Vibration analysis is the cornerstone of predictive maintenance programs, and
the equations for calculating expected vibration frequencies for bearings and toothed gear sets are widely
available. Cycloidal reducers present a special case due to the nature of their reduction mechanism. This paper
will describe a method for utilizing vibration analysis in order to identify a defective Cycloidal ring gear housing,
disc, and eccentric bearing.
ISBN: 1-55589-932-5 Pages: 25
08FTM03. Effects of Gear Surface Parameters on Flank Wear

Authors: J.C. Wang, J. Chakraborty, and H. Xu
Non-uniform gear wear changes gear topology and affects the noise performance of a hypoid gear set. This paper
presents the effects of gear surface parameters on gear wear and the measurement/testing methods used to
quantify the flank wear in laboratory tests. Gear tooth profile, transmission error, gear tooth surface finish
determined by cutting, and gear tooth surface finish determined by other processes are the factors considered in
this paper. The measurements include transmission error, pattern rating, and surface roughness before and after

test. The effects and interaction between controlled factors provided the information for product improvement. The
action resulted from this study is anticipated to significantly improve product reliability and customer satisfaction.
ISBN: 1-55589-933-2 Pages: 15
08FTM04. The Effect of Manufacturing Microgeometry Variations on the Load Distribution Factor and on Gear
Contact and Root Stresses
Authors: D. Houser
Traditionally, gear rating procedures directly consider manufacturing accuracy in the application of the dynamic
factor, but only indirectly through the load distribution consider such errors in the calculation of stresses used in
the durability and gear strength equations. This paper discusses how accuracy affects the calculation of stresses
and then uses both statistical designs of experiments and Monte Carlo simulation techniques to quantify the
effects of different manufacturing and assembly errors on root and contact stresses. Manufacturing deviations to
be considered include profile and lead slopes and curvatures, as well as misalignment. The effects of spacing
errors, runout and center distance variation will also be discussed.
ISBN: 1-55589-934-9 Pages: 15
08FTM05. Gear Failure Analysis Involving Grinding Burn

Authors: G. Blake, M. Margetts, and W. Silverthorne
Aerospace gears require post case-hardening grinding of the gear teeth to achieve their necessary accuracy.
Tempering of the case hardened surface, commonly known as grinding burn, occurs in the manufacturing process
when control of the heat generation at the surface is lost.
A gearbox with minimal service time was removed in service from an aircraft, disassembled, and visual inspection
performed. Linear cracks along the dedendum of the working gear tooth face were found in three adjacent teeth.
A detailed inspection of the gearbox found no other components with distress.
ANSI/AGMA 14104-A17 provides details of the temper etch process and exclusively uses a Nitric acid etch
process, which is typically used in production quality inspections. The incident gear was processed for grinding
burn using an Ammonium Persulfate etch solution. Quality records documented variation in chemical
concentration levels during the time the failed gear was manufactured. A design of experiments was conducted to
understand the effects of the factors and interactions that impact the capability of the Ammonium Persulfate
process used in production to detect grinding burn.
Presented are the metallurgical findings, load distribution analysis of actual geometry, crack propagation analysis,
and design of experiment results of the Ammonium Persulfate etch process.
ISBN: 1-55589-935-6 Pages: 10
08FTM06. Tooth Fillet Profile Optimization for Gears with Symmetric and Asymmetric Teeth
Authors: A. Kapelevich and Y. Shekhtman
Involute flanks are nominally well described and classified by different standard accuracy grades, depending on
gear application and defining their tolerance limits for such parameters as runout, profile, lead, pitch variation, and
others.
The gear tooth fillet is an area of maximum bending stress concentration. However, its profile is typically
marginally described as a cutting tool tip trajectory. Its accuracy is defined by a usually generous root diameter
tolerance. The most common way to reduce bending stress concentration is application of the basic (or
generating) rack with full radius.
This paper presents a fillet profile optimization technique based on the FEA and random search method, which
allows for a substantial bending stress reduction, by 15 to 30% compared to traditionally designed gears. This
reduction results in higher load capacity, longer lifetime, and lower cost. It includes numerical examples confirming
the benefits of fillet optimization.
ISBN: 1-55589-936-3 Pages: 11
08FTM07. Planetary Gearset Lubrication Requirement Estimation Based on Heat Generation

Authors: H. Kim, S. McKenny, D. Zini, J. Chen and N. Anderson
A planetary gearset is composed of sun gear, planet gears, ring gear, carrier and bearings. As the gearset is in
motion under torque, heat is generated at all sliding and rolling contacts for gear meshes and bearing surfaces as
lubricant is supplied. Without lubrication the gearset cannot operate properly because all contact surfaces are
influenced by heat and subsequent damages. On the other hand, excessive lubrication could cause a significant
heat generation as churning or dragging losses increase. It is very important to predict a right amount of
lubrication required for each component and to supply a necessary amount of lubricant in an effective way.
Empirical data of temperature increase inside a planetary gearset at different inlet lubrication temperature, torque
and speed are presented with physical explanation. It has been attempted to utilize heat generation data as an
indicator for required lubrication measure and also for gearset efficiency measure. Heat generation sources are

classified to examine largest and smallest contributors and then project a better way to effective lubrication for the
planetary gearset. Some published gear efficiency equations are examined with power loss calculations based on
gearset heat generations which are empirically measured in the present study.
ISBN: 1-55589-937-0 Pages: 17
08FTM08. PM Materials for Gear Applications

Authors: S. Dizdar, A. Flodin, U. Engström, I. Howe and D. Milligan
The latest material and process developments in powder metal (PM) gears have increased their load capacity.
These new developments allow PM to fully compete with hardened machined wrought gears in a variety of power
transmission applications. New grades of PM materials that can be case hardened using the same conditions as
wrought materials improve their load capacity. Increased load capacity is also achieved by surface densifying gear
teeth deeper than case hardened depth requirements. Since tooth Hertzian and bending stress gradients are
within the fully dense layer, PM gears are virtually equivalent to wrought gears. The performance is demonstrated
by gear tooth bending and RCF data on prototype gears.
ISBN: 1-55589-938-7 Pages: 9
08FTM09. Concept for a Multi Megawatt Wind Turbine Gear and Field Experience
Authors: T. Weiss and B. Pinnekamp
The increasing call for the use of renewable energy in all industrial countries demands for the extension of wind
power generation capacity. In central Europe, as in parts of the Americas and Asia, such further expansion is only
possible by re-powering— replacement of existing turbines by higher rated ones—or by developing locations in
the open sea—offshore. To this end, the gear industry worldwide is challenged to develop and supply the required
number of reliable 5 MW class wind turbine gears.
This paper summarizes the concept evaluation and design of the 5 MW Multibrid® wind turbine transmission
arrangement, test bed measurements with the prototype, as well as field experience over a test period of 3 years.
ISBN: 1-55589-939-4 Pages 11
08FTM10. The Effect of Superfinishing on FZG Gear Micropitting – Part II

Authors: L. Winkelmann and M. Bell
The most common failure mechanism of highly stressed case carburized gears is micropitting (grey staining). The
standard FZG gear test (FVA Work Sheet 54) is generally used to determine the micropitting load capacity of gear
lubricants. In recent years, FZG gear testing has also demonstrated its usefulness for evaluating the effect of
superfinishing on increasing the micropitting load capacity of gears. Results from the Technical University of
Munich were previously presented in Part 1 of this paper. Part II will present the results of Ruhr University
Bochum. Both research groups concluded that superfinishing is one of the most powerful technologies for
significantly increasing the load carrying capacity of gear flanks.
ISBN: 1-55589-940-0 Pages: 10
08FTM11. Bending Fatigue Tests of Helicopter Case Carburized Gears: Influence of Material, Design and
Manufacturing Parameters
Authors: G. Gasparini, U. Mariani, C. Gorla, M. Filippini, and F. Rosa
For helicopter gears many aspects of design and manufacturing must be analyzed, such as material cleanliness,
case depth and hardness, tooth root shape and roughness, and compressive residual stresses. Moreover, these
gears are designed to withstand loads in the gigacycle field, but are also subjected to short duration overloads.
Therefore, a precise knowledge of the shape of the S-N curve is of great importance for assessing their in-service
life.
A single tooth bending (STB) test procedure has been developed to optimally map gear design parameters and a
test program on case carburized, aerospace standard gears has been conceived and performed in order to
appreciate the influence of various technological parameters on fatigue resistance, and to draw the curve shape
up to the gigacycles region.
The program has been completed by failure analysis on specimens and by static tests. Some accessory
investigations, like roughness and micro-hardness measurements, have also been performed. Gigacycle tests
confirm the estimations done on the basis of the shorter tests, both in term of fatigue limit and of curve shapes.
ISBN: 1-55589-941-7 Pages: 12
08FTM12. In-situ Measurement of Stresses in Carburized Gears via Neutron Diffraction

Authors: R. LeMaster, B. Boggs, J. Bunn, J. Kolwyck, C. Hubbard, and W. Bailey
The total stresses in a mating gear pair arise from two sources: 1) externally induced stresses associated with the
transmission of power, and 2) residual stresses associated with the heat treatment and machining of the tooth
profiles. The stresses due to power transmission are the result of complex normal and shearing forces that
develop during the meshing sequence. The total stress from these two sources contributes to the life of a gear.

This paper, funded by the AGMA Foundation, presents the results of research directed at measuring the total
stress in a pair of statically loaded and carburized spur gears. Measurements were made using neutron diffraction
methods to examine the change in total stress as a function of externally applied load and depth below the
surface. The paper includes a summary of the various test methods that were used and a discussion of their
applicability to carburized gears.
ISBN: 1-55589-942-4 Pages: 10
08FTM13. Hydrogen & Internal Residual Stress Gear Failures – Some Failure Analyses and Case Studies
Author: R. Drago
Hydrogen and internal stress failures are relatively rare; however, when they occur they are often very costly and
sometimes quite catastrophic. While hydrogen and internal stress issues are generally recognized as significant in
the design and manufacture of larger gears, they are also important for smaller gears as well.
This paper presents, via illustrated actual case studies, the mechanisms by which these failures occur, the
manner in which they progress, and methods for testing finished gears for the possibility of internal problems. In
addition, precautionary steps that can be taken during design, manufacture, heat treatment and quality control to
minimize the possibility of these problems occurring in a finished part along with similar steps required to prevent
any flawed gears from entering service are also presented and discussed.
ISBN: 1-55589-943-1 Pages: 11
08FTM14. Effects of Axle Deflection and Tooth Flank Modification on Hypoid Gear Stress Distribution and
Contact Fatigue Life
Authors: H. Xu, J. Chakraborty, and J.C. Wang
Flank modifications are often made to overcome the influences of errors coming from manufacturing and
assembly processes, as well as deflections of the system. This paper presents a semi-analytical approach on
estimating the axle system deflections by combining computer simulations and actual loaded contact patterns
obtained from lab tests. By using an example hypoid gear design, influences of axle deflections and typical flank
modifications (lengthwise crowning, profile crowning and twist) on stress distribution of the hypoid gear drive are
simulated. Finally, several experimental gear samples are made and tested. Tooth surface topography is
examined by using a Coordinate Measuring Machine. Test results are reported to illustrate the effect of tooth flank
modifications on contact fatigue life cycles.
ISBN: 1-55589-944-8 Pages: 11
08FTM15. Extending the Benefits of Elemental Gear Inspection

Author: I. Laskin
It may not be widely recognized that most of the inspection data supplied by inspection equipment following the
practices of AGMA Standard 2015 and similar standards are not of elemental accuracy, deviations but of some
form of composite deviations. This paper demonstrates the validity of this “composite” label by first defining the
nature of a true elemental deviation, and then, by referring to earlier literature, demonstrating how the common
inspection practices for involute, lead (on helical gears), pitch, and in some cases, total accumulated pitch,
constitute composite measurements. The paper further explains how such measurements often obscure the true
nature of the individual deviations. It also contains suggestions as to some likely source of the deviation in various
gear manufacturing processes, and how that deviation may affect gear performance. It further raises the question
of the likely inconsistencies of some of these inspection results and of inappropriate judgments of gear quality,
even to the point of the rejection of otherwise satisfactory gears. Finally, there are proposals for modifications to
inspection software, possibly to some inspection routines, all to extending the benefits of the basic elemental
inspection process.
ISBN: 1-55589-945-5 Pages: 12
08FTM16. Hob Tool Life Technology Update

Author: T. Maiuri
The method of cutting teeth on a cylindrical gear by the hobbing process has been in existence since the late
1800's. Advances have been made over the years in both the machines and the cutting tools used. This paper will
examine hob tool life and the many variables that affect it. It will cover the state of the art cutting tool materials and
coatings, hob tool design characteristics, process speeds and feeds, hob shifting strategies, wear characteristics,
etc. The paper will also discuss the use of a common denominator method for evaluating hob tool life in terms of
meters [or inches] per hob tooth as an alternative to tool life expressed in parts per sharpening.
ISBN: 1-55589-946-2 Pages: 15
08FTM17. Innovative Concepts for Grinding Wind Power Energy Gears

Author: C. Kobialka
Over the past years, wind power energy has gained greater importance to reduce CO2 emissions and thus
antagonize global warming. The development of wind power is driven by increased performance, which requires
larger wind turbines and gear boxes. The quality demands of those gears are increasing while the production cost

must decrease. This requires new production methods to grind the gears. Profile grinding is known as a process
to achieve highest possible quality, even for complex flank modifications, while threaded wheel grinding is known
for high productivity. New machine concepts make it now possible to use both advantages at the same time.
This paper will show the newest developments for cycle time reduction and increased work piece quality using
tool change systems to be able to use different grinding wheels for rough and finishing operation, work piece
clamping systems, and concepts of process integration for one work piece flow.
ISBN: 1-55589-947-9 Pages: 12
08FTM18. Gear Corrosion During the Manufacturing Process

Authors: G. Blake and G. Sroka
No matter how well gears are designed and manufactured, gear corrosion can occur that may easily result in
catastrophic failure. Since corrosion is often difficult to observe in the root fillet region or in fine pitched gears with
normal visual inspection, it may well go undetected. This paper presents the results of an incident that occurred in
a gear manufacturing facility several years ago that resulted in pitting corrosion and intergranular attack (IGA). It
shows that superfinishing can mitigate the damaging effects of IGA and pitting corrosion, and suggests that the
superfinishing process is a superior repair method for corrosion pitting versus the current practice of glass
beading.
ISBN: 1-55589-948-6 Pages: 13
08FTM19. How Are You Dealing with the Bias Error in Your Helical Gears?
Author: J. Lange
Using illustrations this paper explains that bias error (“the twisted tooth phoneme”) is a by-product of applying
conventional radial crowning methods to produced crowned leads on helical gears. The methods considered are
gears that are finished, shaped, shaved, form and generated ground. The paper explains why bias error occurs in
these methods, and then addresses what techniques are used to limit/eliminate bias error. Profile and lead
inspection charts will be used to detail bias error and the ability to eliminate it.
The paper details the simultaneous interpolation of multiple axes in the gear manufacturing machine to achieve
the elimination of bias error. It also explains that CNC machine software can be used to predict bias error, and
equally important that it could be used to create an “engineered bias correction” to increase the load carrying
capacity of an existing gear set.
ISBN: 1-55589-949-3 Pages: 14
2007 PAPERS
07FTM01. Estimation of Lifetime of Plastic Gears
Author: S. Beermann
This paper gives an overview on the state of art in plastic gear resistance calculation. The main problem with
plastics is the dependency of the stress cycle curve (Woehler line) with temperature. Today, more plastic gears
(as in automobile headlights) are used in a high temperature range. Furthermore, flank resistance depends
strongly on lubrication (lifetime may vary by a factor of ten and more, if oil, grease lubricated or dry running).
As no secure data for plastic gears is available, how can nevertheless plastic gear design and life time prediction
be improved? The best strategy is to use the feedback of existing reducers. Plastic gearboxes, before starting
production in big series, are normally submitted to endurance tests. If these tests are used to check also the real
lifetime limits — or by increasing test length, or by increasing applied torque — these results can be used to
define the required safety factors for future gear design. This procedure has been very successful, and will be
described with some examples.
ISBN: 1-55589-905-9 Pages: 14
07FTM02. Study of the Correlation Between Theoretical and Actual Gear Fatigue Test Data on a Polyamide
Author: S. Wasson
Fatigue tests have been run on actual molded gears in order to provide design data, using fully lubricated, plastic
on plastic spur gears in a temperature controlled experiment. The purpose of the testing is to see if there is a good
correlation between fatigue data, generated in a lab on test bars, versus the actual fatigue performance in a gear.
In order to do this, the theories of gear calculations to get root stresses also had to be examined. Advanced FEA
showed that there are corrections needed to account for high loading or high temperatures in plastic gears. The
chemistry of various nylons used in gears is explained. A high crystalline nylon has been found which is an
excellent material for gears in demanding applications and can withstand high torques and operating
temperatures. The material has very good wear properties and excellent retention of mechanical properties
(strength, stiffness, and fatigue) especially at elevated temperatures. Several commercial gear applications are
currently utilizing these properties. These will be shown to demonstrate the benefits and manufacturability of this
material.
ISBN: 1-55589-906-6 Pages: 6

07FTM03. Material Integrity in Molded Plastic Gears and Its Dependence on Molding Practices
Author: T. Vale
The quality of molded plastic gears is typically judged by dimensional feature measurements only. This practice
overlooks potential deficiencies in the plastic injection molding process and its effect on the integrity of the plastic
material. These deeper issues are often not given proper consideration until a related gear failure demands its
study and evaluation. This paper identifies some of these oversights in the molding process, the resultant effect
on the plastic material, and discusses their likely effect on short and long term gear performance.
ISBN: 1-55589-907-3 Pages: 11
07FTM04. Applying Elemental Gear Measurement to Processing of Molded Plastic Gears

Author: G. Ellis
Although elemental gear inspection is rarely specified for molded plastic gears, the measurement equipment and
practices can be valuable in advancing the molding processes and improving quality. After a brief description of
plastic gear tooling and molding, this paper gives examples of specific elemental measurements and relates them
to process changes and quality improvements. Such examples for spur and helical gears include: profile
measurements, leading to gear mesh noise reduction; lead measurement, leading to increased face width load
distribution and, continuing from that, even to the molding of crowned gears; and index measurement, leading to
improved roundness of gears molded from fiber reinforced plastic materials.
ISBN: 1-55589-908-0 Pages: 10
07FTM05. Vacuum Carburizing Technology for Powder Metal Gears and Parts
Authors: J. Kowalewski and K. Kucharski,
Carburizing is one of the leading surface hardening processes applied to the sintered, low-alloyed steel gears in
the automotive industry. While diffusion of carbon in wrought steel is well documented, this is not the case for PM
steel subject to carburizing in vacuum furnaces. This paper presents results that show that the density of the
powder metal is the main factor for the final carbon content and distribution. Also important is the state of the
surface of the part; either sintered with open porosity or machined with closed porosity. The way the carburizing
gas moves through the furnace might be of some influence as well.
ISBN: 1-55589-909-7 Pages: 5
07FTM06. Using Barkhausen Noise Analysis for Process and Quality Control in the Production of Gears
Authors: S. Kendrish, T. Rickert and R. Fix
The use of magnetic Barkhausen Noise Analysis (BNA) has been proven to be an effective tool for the non-
destructive detection of microstructural anomalies in ferrous materials. Used as an in-process tool for the
detection of grinding burn, heat treat defects and stresses, BNA is a quick comparative and quantitative
alternative to traditional destructive methods.
This paper presents examples that demonstrate how BNA is used to evaluate changes in microstructural
properties. Quantitative results correlate BNA test values to x-ray diffraction values for the detection of changes in
residual stress. Qualitative results correlate BNA test values to acid etch patterns/colors for the detection of
grinding burn defects.
ISBN: 1-55589-910-3 Pages: 5
07FTM07. Grinding Induced Changes in Residual Stresses of Carburized Gears

Authors: R. LeMaster, B. Boggs, J. Bunn, C. Hubbard, and T. Watkins
This paper presents the results of a study performed to measure the change in residual stress that results from
the finish grinding of carburized gears. Residual stresses were measured in five gears using the x-ray diffraction
equipment in the Large Specimen Residual Stress Facility at Oak Ridge National Laboratory. Two of the gears
were hobbed, carburized, quenched and tempered, but not finished. The remaining three gears were processed
similarly, but were finish ground. The residual stresses were measured at 64 different locations on a tooth from
each gear. Residual stresses were also measured at fewer points on other teeth to determine the tooth-to-tooth
variation. Tooth profile measurements were made of the finished and unfinished gear samples.
The results show a fairly uniform and constant compressive residual field in the non-finished gears. There was a
significant reduction in the average residual stress measured in the finished gears. Additionally, there was a
significant increase in the variability of the residual stress that was introduced by the grinding process. Analysis of
the data suggests a linear relationship between the change in average residual stress and the amount of material
removed by the grinding process.
ISBN: 1-55589-911-0 Pages: 14
07FTM08. Manufacturing Net Shaped Cold Formed Gears

Author: D. Engelmann
An innovative metal forming process has been developed for manufacturing quality, durable and cost efficient
gears for high volume production. In this paper, the development of net shaped Cold Formed Gears (CFG) is

presented along with their suitable applications. The manufacturing technique and equipment is introduced, as
well as the advantages and limitations. Applicable materials and heat treatment practices are also discussed.
Gear tooth inspection charts are presented and compared to conventional manufacturing methodologies.
ISBN: 1-55589-912-7 Pages: 7
07FTM09. The Ikona Clutch and Differential

Authors: J. Colbourne, V. Scekic, and S. Tesic
This paper describes two devices, a clutch and a differential, which are based on the Ikona CVT. This CVT is
essentially an internal gear pair, in which the pinion is mounted on an eccentric that can drive or be driven by an
electric motor/generator, thus providing a variable ratio. Since this arrangement allows for “branching” of energy
flow(s), it can be classified as summation-type CVT.
When the CVT is used as a clutch, it would replace the friction-plate clutch in vehicles with standard
transmissions, and the fluid torque converter in automatic transmissions. The new clutch will be referred to as the
electric torque converter. Any excess energy is converted into electrical energy, and either stored in the battery, or
reintroduced into the system through the motor/generator. Modulation of the clutch can be very smooth which is
particularly advantageous when the vehicle starts from rest on uphill slopes. Since no friction element is involved,
and only a fraction of torque is being manipulated, the modulation can be repeatable regardless of conditions.
Finally, in a hybrid-vehicle arrangement, the clutch can be used to maintain the engine at its optimum speed
(within limits), regardless of the road speed and the gearbox ratio.
Similar principals apply to the Ikona differential. Unlike today's limited slip differentials, the Ikona differential allows
full torque to be transmitted through one drive wheel, even though the other drive wheel may have completely lost
traction. Unlike traditional differentials that allow wheels to rotate at different speeds, the Ikona differential forces
the wheels to do so. Accordingly, when the vehicle is changing direction, the differential can be used to control the
speed of each drive wheel, thus providing active torque steering.
ISBN: 1-55589-913-4 Pages: 6
07FTM10. The Gear Dynamic Factor, Historical and Modern Perspective

Authors: D. Houser and D. Talbot
The dynamic factor has been included in gear design and rating formulas since the 1930's. Its original formulation
was based on an assessment of entering tooth impacts, but in modern gear design procedures, where tip relief
and lead modifications are common, these impacts may be virtually eliminated. With this elimination, one finds
that gear dynamics are mainly excited by steady state phenomena such as transmission error, friction and axial
shuttling of the mesh force. This paper will first provide a historical progression of the dynamic factor equations
that are based on impact theory and will define when this methodology is appropriate. The paper will then discuss
the various steady state modeling approaches and will use one of these approaches to demonstrate the effects of
manufacturing deviations on predicted dynamic loads.
ISBN: 1-55589-914-1 Pages: 11
07FTM11. Helicopter Accessory Gear Failure Analysis Involving Wear and Bending Fatigue
Authors: G. Blake and D. Schwerin
Gear tooth wear is a very difficult phenomenon to predict analytically. The failure mode of wear is closely
correlated to the lambda ratio, and can manifest into more severe failure modes, such as bending. Presented is a
failure analysis in which this occurred. A legacy aerospace gear mesh experienced nine failures within a two-year
time period. The failures occurred after more than eight years in service and within tight range of cycles to one
another. Each failure resulted in the loss of all gear teeth with origins consistent with classic bending fatigue.
Non-failed gears, with slightly lower time than the failed gears, were removed from service and inspected. Gear
metrology measurements quantified a significant amount of wear. The flank form of these worn gears was
measured and the measured data used to analytically predict the new dynamic load distribution and bending
stress. To predict if the failure mode of wear was expected for this gear mesh, an empirical relationship of wear to
lambda ratio was created using field data from multiple gear meshes in multiple applications. Presented are the
metallurgical failure analysis findings, dynamic gear mesh analysis, the empirical wear rate curve developed, and
design changes.
ISBN: 1-55589-915-8 Pages: 12
07FTM12. The Effect of Start-Up Load Conditions on Gearbox Performance and Life – Failure Analysis and
Case Study
Author: R.J. Drago
When gearboxes are used in applications in which the connected load has high inertia, the starting torque
transmitted by the gearbox can be much higher than the rated load of the prime mover. Power plants often require
several evaporative cooling towers or large banks of air cooled condensers (ACC) to discharge waste heat.
Because of the very large size of the fans used in these applications, they fall into this category of high inertia
starting load devices. When started from zero speed, a very high torque is required to accelerate the fan to normal

operating speed. If the fan is started infrequently and run continuously for long periods of time, this high starting
torque is of minimal significance. However, when the fan is started and stopped frequently, the number of cycles
at the high starting torque can accumulate to a point where they can cause extensive fatigue damage, even if the
gear system is adequately rated.
Where the gear unit is marginally rated, very early, catastrophic gear failure is often the result. As part of the
overall investigation of several failures in such gearboxes, we measured starting torque on a typical installation,
examined many failed gears, and calculated the load capacity ratings for the gearboxes under actual operating
conditions. This paper describes the failures observed, the testing conducted, the data analyses and the effect of
the high measured starting torque on the life and performance of the gear systems. The test results revealed
surprising results, especially during starts where the fan was already wind-milling due to natural air flow in the
ACC bank.
ISBN: 1-55589-916-5 Pages: 12
07FTM13. Influence of Grinding Burn on the Load Carrying Capacity of Parts under Rolling Stress
Authors: F. Klocke, T. Schröder and C. Gorgels
The demand for continuous improvement concerning economic efficiency of products and processes leads to an
increasing cost pressure in manufacturing and design of power transmissions. Also, the power density of gears
has been increased which leads to a demand for higher gear quality. In more and more cases this can only be
achieved using hard finishing processes.
The demand for higher gear qualities leads to an increased use of gear grinding, which incurs the risk of thermal
damage, such as grinding burn on the gear flank. The influence of thermal damage on the set in operation is
nevertheless hard to judge so that damaged gears are often scrapped. This leads to increasing failure costs.
The lack of knowledge of the effect of grinding burn on the load carrying capacity of gears leads to the point that
the same degree of damage is judged differently by different companies. Therefore, it is necessary to do trials with
thermally damaged parts in order to know how much a certain degree of thermal damage influences the load
carrying capacity.
The investigations described in this report are aimed at determining the load carrying capacity of parts under
rolling stress. Thermally damaged rollers are employed on a roller test rig, since with this analogy process the part
geometry is easier to describe and easier to damage reproducibly.
ISBN: 1-55589-917-2 Pages: 10
07FTM14. Roughness and Lubricant Chemistry Effects in Micropitting

Authors: A. Olver, D. Dini, E. Lainé, D. Hua, and T. Beveridge
Micropitting has been studied using a disc machine in which a central carburized steel test roller contacts three,
harder, counter-rollers with closely controlled surface roughness. Roughness was varied using different finishing
techniques, and the effects of different oil base-stocks and additives were investigated.
Damage on the test rollers included dense micropitting and “micropitting erosion” in which tens of microns of the
test surface were completely removed. This phenomenon is particularly damaging in gear teeth where it has the
potential to destroy profile accuracy. It was found that anti-wear additives led to a high rate of micropitting erosion,
and the effect correlated more or less inversely with simple sliding wear results. There were also appreciable
effects from base-stock chemistry.
The key parameter affecting the severity of damage seemed to be the near-surface shear stress amplitude arising
from the evolved roughness; different chemistries led to the evolution of different roughness during initial running
and to different contact stresses and levels of damage.
ISBN: 1-55589-918-9 Pages: 8
07FTM15. Experience with a Disc Rig Micropitting Test

Authors: M. Talks and W. Bennett
The experimental work carried out was aimed at developing a test method that was able to consistently produce
micropitting damage and could discriminate between good oil (i.e., one that rarely produces micropitting in
service) and a poor oil (i.e., one that does produce micropitting in service).
The disc rig control system allows test parameters such as entrainment velocity, contact stress and slide/roll ratio
at the disc/roller contacts to be accurately and independently controlled. This enables the effect of key parameters
to be studied in isolation, which is something that cannot be easily achieved using conventional gear test rigs.
A test procedure has been developed which provides a good level of repeatability and discrimination between oils.
In addition, a study of the effect of slide/roll ratio (SRR) has shown that the severity of micropitting damage
increases as SRR increased, whereas at 0% SRR no micropitting occurred, and, at negative SRRs, microcracking
occurred, but not micropitting. This is the way that SRR seems to affect micropitting in gears.
ISBN: 1-55589-919-6 Pages: 9

07FTM16. Straight Bevel Gear Cutting and Grinding on CNC Free Form Machines
Author: H. Stadtfeld
Manufacturing of straight bevel gears was in the past only possible on specially-dedicated machines. One type of
straight bevel gears are those cut with a circular cutter with a circumferential blade arrangement. The machines
and the gears they manufacture have the Gleason trade name Coniflex®. The cutters are arranged in the
machine under an angle in an interlocking arrangement which allows a completing cutting process. The two
interlocking cutters have to be adjusted independently during setup, which is complicated and time consuming.
The outdated mechanical machines have never been replaced by full CNC machines, but there is still a
considerable demand in a high variety of low quantities of straight bevel ears. Just recently it was discovered that
it is possible to connect one of the interlocking straight bevel gear cutter disks to a free form bevel gear generator
and cut straight bevel gears of identical geometry compared to the dedicated mechanical straight bevel gear
generator. A conversion based on a vector approach delivers basic settings as they are used in modern free form
machines. The advantages are quick setup, high accuracy, easy corrections and high repeatability.
ISBN: 1-55589-920-2 Pages: 10
07FTM17. Simulation Model for the Emulation of the Dynamic Behavior of Bevel Gears
Authors: C. Brecher, T. Schröder and A. Gacka
The impact of bevel gear deviations on the noise excitation behavior can only be examined under varying working
conditions such as different rotational speed and torque. The vibration excitation of bevel gears resulting from the
tooth contact is primarily determined by the contact conditions and the stiffness properties of the gears. By the use
of a detailed tooth contact analysis, the geometry based gear properties can be developed and provided for a
dynamical analysis of the tooth mesh.
A model has been developed for the simulation of the dynamic behavior of bevel gears. With the aid of a load-free
tooth contact analysis, the geometry-based part of the path excitation is determined. With a tooth contact analysis
under load, the path excitation caused by deflections can be calculated. The geometry based part of the path
excitation and a characteristic surface of the excitation values is created and provided for dynamic simulation.
This dynamic model is able to consider every deviation of the micro- and macrogeometry from the ideal flank
topography, i.e., waves and/or grooves in the surface structure, in combination with two and three dimensional
flank deviations like profile deviations, helix deviations and twists. It is also possible to consider the influence of
friction and the contact impact caused by load and/or manufacturing errors with a test rig to verify the calculations.
ISBN: 1-55589-921-9 Pages: 8
07FTM18. Bevel Gear Model

Author: Ted Krenzer
The paper presents a method for developing an accurate generic bevel gear model including both the face milling
and face hobbing processes. Starting with gear blank geometry, gear and pinion basic generator machine settings
are calculated. The contact pattern and rolling quality are specified and held to the second order in terms of
pattern length, contact bias and motion error. Based on the setup, a grid of tooth points are found including the
tooth flank, fillet and, if it exists, the undercut area. It is proposed as the model for the next generation of bevel
gear strength calculations in that the procedure produces true bevel gear geometry, uses blank design
parameters as input and is vendor independent except for cutter diameter.
ISBN: 1-55589-922-6 Pages: 10
07FTM19. How to Determine the MTBF of Gearboxes

Author: G. Antony
Mean Time Between Failures (MTBF) became a frequently used value describing reliability of components,
assemblies, and systems. While MTBF was originally introduced and used mainly in conjunction with electronic
components and systems, the definition and application for mechanical components, such as gearboxes, is not
broadly available, used, or recognized. In the field of gears, it is difficult to obtain an MTBF from the manufacturer
due to the lack of applicable, generally recognized definitions and standards. The paper will evaluate, compare
and suggest ways in determining a gearbox MTBF based on the already established, proven, design calculation
standards and test methods used in the gear design.
ISBN: 1-55589-923-3 Pages: 9

2006 PAPERS
06FTM01. The Effects of Super Finishing on Bending Fatigue
Author: G. Blake
A super finishing study was designed and conducted for bending fatigue. AMS6265 parts were created: with and
without super finishing. Bending fatigue was tested using Single Tooth Fatigue (STF) and RR Moore rotating
beam methods. The STF parts were designed with tooth geometry replicating a spiral bevel gear section. Two lots
of material were processed. Thus, a minimum of two carburized and hardened lots, two shot peen batches and
two super finishing cycles (if applicable) were processed per sample group. A detailed metallurgical evaluation
was performed to characterize the material and compare to actual spiral bevel gears. Analysis of the test data
concluded no statistical difference in bending fatigue strength.
ISBN: 1-55589-883-1 Pages: 14
06FTM02. Isotropic Superfinishing of S-76C+ Main Transmission Gears

Authors: B. Hansen, M. Salerno and L. Winkelmann
Isotropic superfinishing was applied to the third stage spur bull gear and mating pinions along with the second
stage bevel gears of a Sikorsky S-76C+ main gearbox. The gearbox completed the standard Acceptance Test
Procedure (ATP) and a 200-hour endurance test. During these tests noise, vibration, and operating temperatures
were shown to be significantly reduced due to lower friction. A description of the tests, performance data and a
general description of the process is presented.
ISBN: 1-55589-884-7 Pages: 12
06FTM03. Detailed Procedure for the Optimum Design of an Epicyclic Transmission Using Plastic Gears
Authors: I. Regalado and A. Hernández
Shows the steps to get an optimum (volume based) design for an epicyclic transmission using plastic materials,
the tooth proportions of ANSI/AGMA 1006-A97, the recommendations given in ANSI/AGMA 6023-A88, and
ANSI/AGMA 2101-C95. It gives the effect of changing the number of planets, the bending fatigue and contact
strength of the plastic materials, and the temperature effects on the size of the gears. The design procedure starts
with a preliminary analysis of gear performance in a proposed (not optimized) transmission; going step by step to
an optimum design for the given load conditions and expected minimum life.
ISBN: 1-55589-885-8 Pages: 11
06FTM04. Precision Planetary Servo Gearheads

Authors: G.G. Antony and A. Pantelides
Automated machines use servomotors to perform complex motions. Planetary gearheads are frequently used in
conjunction with servomotors to match the inertias, lower the speed, boost the torque, and at the same time
provide a mechanical interface for pulleys, cams, drums and other mechanical components. This paper covers
topics such as: reasons why planetary gear systems are chosen for “servo applications”; what influences the
planetary servo gear positioning accuracy and repeatability; rating practices to establish a “comparability” of
different torques; and, an introduction of a simple method to determine the required gearbox torque rating for a
servo-application based on motor torque data.
ISBN: 1-55589-886-6 Pages: 11
06FTM05. Development of a Gear Rating Standard – A Case Study of AGMA 6014-A06

Author: F.C. Uherek
The AGMA Mill Gearing Committee completed AGMA 6014 for grinding mill and kiln service gear rating. The
approach the committee took in the development of this standard to determine the content is reviewed. Through a
review of previous standards, the performance history of applications for long life (over 20 years), and considering
the large gear size, the committee achieved consensus on a rating method, which was derived from ANSI/AGMA
2001-D04. A factor comparison between 6014 and 2001 is presented, as well as their interaction, to explain the
goal of the committee to develop a document that reflects actual field experience of in-service operating gear sets.
ISBN: 1-55589-887-4 Pages: 8
06FTM06. An Analytical Approach to the Prediction of Micropitting on Case Carburized Gears

Authors: D. Barnett, J.P. Elderkin and W. Bennett
Micropitting is an area of gear failure that influences gear noise and transmission error. This paper outlines an
approach to analyzing micropitting by looking at the critical factors for a given gear design. A practical procedure,
which incorporates a three-dimensional spring model, was used to predict the micropitting wear rate and the
position that wear would take place on test gear pairs. Case studies have been included that directly compare the
predicted levels of micropitting with those actually measured. Simplified formulations suitable for manual
calculations are also discussed.
ISBN: 1-55589-888-2 Pages: 15

06FTM07. Improvement of Standardized Test Methods for Evaluating the Lubricant Influence on Micropitting
and Pitting Resistance of Case Carburized Gears
Authors: B.-R. Höhn, P. Oster, T. Radev, G. Steinberger and T. Tobie
Micropitting and pitting are fatigue failures that occur on case carburized gears. The performance of lubricants in
regard to micropitting and pitting can be evaluated by test methods. The FVA-FZG-micropitting test consists of
two parts: a load stage test followed by an endurance test. The tests require relatively high costs and are time
consuming. Therefore, an analogous short test method was developed to classify candidate lubricants and
supplement the existing test. The results of the short test method are given. The FVA-FZG-pitting test is for
limited-life using test gears, which are ground without controlled profile or helix modifications. Although the flank
roughness is restricted, the appearance of micropitting can cause a wide statistical spread of pitting test life. Thus,
there was potential improvement in the test results reproducibility. In the test gears were superfinished to prevent
micropitting, and given flank modifications for improved test relevance. The paper describes test procedures and
shows basic examples of test results.
ISBN: 1-55589-889-0 Pages: 11
06FTM08. An Evaluation of FZG Micropitting Test Procedures and Results for the Crowned AGMA Test Gears
Authors: D.R. Houser, S. Shon and J. Harianto
This paper reports on surface fatigue testing. The goal was to develop models for predicting wear. As part of this
goal, the study reports on developing an understanding of the stresses and wear predictors using FZG tests.
Since the focus was on micropitting, the first tests used the method described in FVA Information Sheet
No. 54/I-IV. Later, the procedure was modified to account for higher contact stress levels that are predicted for the
heavily crowned and tip relieved AGMA test gears that were manufactured as a part of the AGMA tribology test
program. This paper provides extensive analysis that includes detailed topography measurements of the tooth
profiles, predictions of contact stresses and contact patterns. It discusses factors that affect contact stresses, flash
temperatures, and test film thickness.
ISBN: 1-55589-890-4 Pages: 12
06FTM09. Opportunities to Replace Wrought Gears with High Performance PM Gears in

Automotive Applications
Authors: U. Engström, D. Milligan, P. Johansson and S. Dizdar
Powder metallurgy (PM) enables production of components with complex geometries such as gears. The cost-
effective use of PM components in automotive applications has showed a continuous growth. This growth is due
to the net shape capability, while maintaining performance. Gears for automotive applications are complex in
shape and require both geometrical accuracy and high mechanical performance in terms of tooth durability. By
utilizing selective densification of the teeth, these performance requirements can be met at a low cost. In this
paper a PM process consisting of compaction, sintering, surface densification, and finally heat treatment has been
studied to assess the feasibility of production. Helical and spur gears were used where the densification, as well
as the resulting gear quality and durability, were tested.
ISBN: 1-55589-891-2 Pages: 7
06FTM10. Fabrication, Assembly and Test of a High Ratio, Ultra Safe, High Contact Ratio, Double Helical
Planetary Transmission for Helicopter Applications
Authors: F.W. Brown, M.J. Robuck, M. Kozachyn, J.R. Lawrence and T.E. Beck
An ultra-safe, high ratio planetary transmission, for application as a helicopter main rotor final drive, has been
designed, fabricated and tested. The transmission improvements are reduced weight, reduced noise and
improved fail-safety and efficiency. This paper discusses the fabrication, assembly and testing of the planetary
transmission. An existing planetary transmission utilized a two-stage conventional spur gear design with fixed
internal ring gears. The new double helical planetary (DHP) system design uses a compound planetary
arrangement with staggered planets and high contact ratio gearing in a unique configuration. Double helical gears
in the planet to ring meshes balance axial tooth forces without axial planet bearing reactions. The spur gear sun to
planet meshes are staggered to achieve a compact arrangement. The sun gear is fully floating.
ISBN: 1-55589-892-0 Pages: 12
06FTM11. On Tooth Failure Analysis in Small-Teeth-Number Gearing: An Analytical Approach

Author: S.P. Radzevich
This paper is an analytical study of tooth failure in gearing having small numbers of teeth. For the analysis, tooth
contact stresses and combined shear stresses are investigated. The study is based on gear tooth loading,
accounting for load variations with time and other gear parameters in various phases of tooth meshing. The
contact and shear stresses are by simultaneous: (a) contact stresses together with (b) stresses caused by the
pinion and gear sliding. While developed for use in gearing with low numbers of teeth, the method can be used for
computation of stresses in gearing having more teeth. The results of the research could be used with AGMA 908-
B89 for gears having less than 12 teeth.
ISBN: 1-55589-893-9 Pages: 22

06FTM12. A Crane Gear Failure Analysis – Case Study, Observations, Lessons Learned, Recommendations
Author: R.J. Drago
The gearboxes used in cranes have proven themselves to be reliable. However, some gear failures have caused
a reevaluation of the design, configuration, and manufacture of gearboxes in large cranes. Since crane gearboxes
do not operate continuously, gear system fatigue characteristics have not been in the forefront of system
operation. Studies have indicated that in many cases usage rates, loading, and in many cases both, have
increased. In some applications, crane usage has increased by factors of two, or three, or even more, and gear
loading has similarly increased. This higher usage makes the cumulative effects of fatigue much more important.
This paper presents a case study of one particular crane gear failure, including failure analysis and resultant
remedial actions, along with a discussion of the results and implications from extensive gearbox inspections that
were conducted as a result of the initial failure.
ISBN: 1-55589-894-7 Pages: 10
06FTM13. Economic Aspects of Vacuum Carburizing

Author: J. Kowalewski
This paper presents the aspects of vacuum carburizing technology that have an impact on process costs and
quality improvements in the final product. There is an interest in furnaces for vacuum carburizing due to the
demand for products with overall metallurgical quality and low unit cost. Vacuum carburizing technology produces
work with minimum distortion, and desired surface metallurgy. Systems can provide “cold to cold” (cold work going
in, cold work coming out) and fully automatic operation that reduces operator involvement, thus minimizing labor.
Considering upstream and downstream requirements, vacuum carburizing can provide a total reduction of costs.
This technology differs considerably from traditional gas carburizing both in the equipment used and in the
process economy.
ISBN: 1-55589-895-5 Pages: 6
06FTM14. The Optimal High Speed Cutting of Bevel Gears – New Tools and New Cutting Parameters
High speed carbide dry cutting improvements have a dependency of many important parameters upon the
particular job situation, which makes it difficult for a manufacturing engineer to establish an optimal cutting
scenario. An analysis of the different parameters and their influence on the cutting process, allows the
establishment of five, nearly independent areas of attention: blade geometry and placement in the cutter head;
cutting edge micro geometry; surface condition of front face and side relief surfaces; speeds and feeds in the
cutting process; and, kinematic relationship between tool and work (climb or conventional cutting, vector feet).
This paper presents explanations and guidelines for optimal high speed cutting depending on cutting method, part
geometry and manufacturing environment. Also, how to choose the blade system, thus giving the manufacturing
engineer information to support optimizing cutter performance, tool life and part quality.
ISBN: 1-55589-896-3 Pages: 13
06FTM15. Optimal Tooth Modifications in Spiral Bevel Gears Introduced by Machine Tool Setting Variation
Author: V. Simon
A method for the determination of optimal tooth modifications in spiral bevel gears based on load distribution,
minimized tooth root stresses, and reduced transmission errors is presented. Modifications are introduced into the
pinion tooth surface considering the bending and shearing deflections of gear teeth, local contact deformations of
mating surfaces, gear body bending and torsion, deflections of the supporting shafts, and manufacturing and
alignment of mating members. By applying a set of machine tool setting parameters, the maximum tooth contact
pressure can be reduced by 5.4%, the tooth fillet stresses in the pinion by 8% and the angular position error of the
driven gear by 48%, based on a spiral bevel gear pair manufactured by machine tool settings determined by a
commonly used method.
ISBN: 1-55589-897-1 Pages: 12
06FTM16. Certificate for Involute Gear Evaluation Software

Author: F. Härtig
A test for the verification of involute gear software has been developed at the Physikalisch-Technische
Bundesanstalt (PTB). This paper shows the critical influence on measurement uncertainty of uncertified involute
evaluation software. Beside the test parameter information, the most dominant effects of software errors will be
explained. The algorithms developed during this project should influence and help complete the existing standards
and their guidelines.
ISBN: 1-55589-898-4 Pages: 5

2005 PAPERS
05FTM01. Fine Pitch, Plastic Face Gears: Design and Manufacture
Authors: I. Laskin and E. Reiter
Face gear technology has attracted attention. Products benefiting include those which use molded plastic gears.
More applications could benefit, justifying the need for more information on the special features of face gears,
their design and manufacture, in comparison to other non-parallel-shaft gears. A description of manufacturing
methods, particularly in plastic molding is given with inter-related design and gear performance issues. New
methods of graphic modeling are included with descriptions of face gear configurations and applications.
ISBN: 1-55589-849-1 Pages: 11
05FTM02. The Effects of Pre Rough Machine Processing on Dimensional Distortion During Carburizing
Author: G. Blake
A study to isolate the influence of pre-rough machine processing on final dimensional distortion. Methods are
discussed to aid process development and minimize dimensional change during carburizing. The study examined
the distortion during carburizing between five possible raw material starting conditions. Coupons were used and
manufactured from each population of material processing. Dimensions were made before and after carburizing
using a scanning coordinate measurement machine. The results show that dimensional distortion during
carburizing increases with mechanical and thermal processing.
ISBN: 1-55589-850-5 Pages: 18
05FTM03. Modeling Gear Distortion

Author: P.C. Clarke
Dealing with carburize case hardened gear distortion and growth is a challenge for the global gear industry.
Attempts started in 1978 with computer programs to calculate distortion and growth, plus residual stress
distributions for a gear and evolved by gathering distortion data for a wide range of sizes, shapes, grinding
allowances with trends for different geometries. A spread sheet program with gear dimensional input, calculates
the distortions and growths, and then calculates the modified dimensions for required protuberance and the
minimum carburized case depth. Case histories illustrate the consequences of various geometries and future
developments are discussed.
ISBN: 1-55589-851-3 Pages: 12
05FTM04. Tooth Meshing Stiffness Optimization Based on Gear Tooth Form Determination for a Production
Process Using Different Tools
Authors: U. Kissling, M. Raabe, M. Fish
The variation of the tooth meshing stiffness is a source of noise and the exact calculation of tooth form is
important for the stiffness determination. For this purpose, software was written with the concept of an unlimited
number of tools such as hobs, grinding disk, and honing defining a manufacturing sequence. Stiffness variation
can be improved by optimization of final gear geometry with a calculation of the contact path under load. The
meshing stiffness is derived making it possible to study the effect of a proposed profile correction of a gear under
different loads. Calculations with AGMA2001 or ISO6336 check the point with the highest root stress. Effect of a
grinding notch is also included.
ISBN: 1-55589-852-1 Pages: 11
05FTM05. Computerized Design of Face Hobbed Hypoid Gears: Tooth Surface Generation, Contact Analysis
and Stress Calculation
Authors: M. Vimercati and A. Piazza
Face milled hypoid gears have been widely studied. Aim of this paper is just to propose an accurate tool for
computerized design of face hobbed hypoid gears. A mathematical model able to compute detailed gear tooth
surface is presented. Then, the obtained surfaces will be employed as input for an advanced contact solver that,
using a hybrid method combining finite element technique with semi analytical solutions, is able to efficiently carry
out contact analysis under light and heavy loads and stress calculation of these gears.
ISBN: 1-55589-853-3 Pages: 13
05FTM06. A Model to Predict Friction Losses of Hypoid Gears

Authors: H. Xu, A. Kahraman and D.R. Houser
A model to predict friction-related mechanical efficiency losses of hypoid gear pairs is proposed, which combines
a commercial available finite element based gear contact analysis model and a friction coefficient model with a
mechanical efficiency formulation. The contact analysis model is used to provide contact pressures and other
contact parameters required by the friction coefficient model. The instantaneous friction coefficient is computed by
using a validated formula that is developed based on a thermal elastohydrodynamic lubrication (EHL) model.
Computed friction coefficient distributions are then used to calculate the friction forces and the resultant
instantaneous mechanical efficiency losses of the hypoid gear pair at a given mesh angle. The model is applied to

study the influence of speed, load, surface roughness, and lubricant temperature as well as assembly errors on
the mechanical efficiency of an example face-hobbed hypoid gear pair.
ISBN: 1-55589-854-8 Pages: 15
05FTM07. Spiral Bevel and Hypoid Gear Cutting Technology Update

Author: T.J. Maiuri
Spiral bevel and hypoid gear cutting technology has changed significantly over the years. The machines, tools,
materials, coatings and processes have steadily advanced to the current state of the art. This paper will cover the
progression from mechanical machines with complex drive trains using the five cut method of cutting gears with
coolant, to machines with direct drive CNC technology dry cutting gears by the completing method with carbide
and high speed steel tools. The latest cutting tool materials and tool coatings will be discussed. Production
examples from the automotive and truck industries will be provided, as well as examples from the gear jobbing
industry.
ISBN: 1-55589-855-6 Pages: 20
05FTM08. New Developments in Tooth Contact Analysis (TCA) and Loaded TCA for Spiral Bevel and Hypoid
Gear Drives
Authors: Q. Fan and L. Wilcox
Tooth Contact Analysis (TCA) and Loaded Tooth Contact Analysis (LTCA) are two powerful tools for the design
and analysis of spiral bevel and hypoid gear drives. TCA and LTCA respectively simulate gear meshing contact
characteristics under light load and under significant load. Application of CNC hypoid gear generators has brought
new concepts in design of spiral bevel and hypoid gears with sophisticated modifications. This paper presents
new developments in TCA and LTCA of spiral bevel and hypoid gears. The first part of the paper describes a new
universal tooth surface generation model with consideration of capabilities of CNC bevel gear generators. The
universal model is based on the kinematical modeling of the basic machine settings and motions of a virtual bevel
gear generator which simulates the hypoid gear generator and integrates both face milling and face hobbing
processes. Mathematical descriptions of gear tooth surfaces are represented by a series of coordinate
transformations in terms of surface point position vector, unit normal, and unit tangent. Accordingly, a generalized
TCA algorithm and program are developed. In the second part of this paper the development of a finite element
analysis (FEA) based LTCA is presented. The LTCA contact model is formulated using TCA generated tooth
surface and fillet geometries. The FEA models accommodate multiple pairs of meshing teeth to consider a
realistic load distribution among the adjacent teeth. An improved flexibility matrix algorithm is formulated by
introducing specialized gap elements with considerations of deflection and deformation due to tooth bending,
shearing, local Hertzian contact, and axle stiffness. Two numerical examples, a face-hobbing design and a face
milling design, are illustrated to verify the developed mathematical models and programs.
ISBN: 1-55589-856-4 Pages: 12
05FTM09. Hypoid Gear Lapping Wear Coefficient and Simulation

Authors: C. Gosselin, Q. Jiang, K. Jenski and J. Masseth
Hypoid gears are usually hard finished after heat treatment using lapping. Because of the rolling and sliding
motion inherent to hypoid gears, the lapping compound abrades and refines the tooth surface to achieve
smoothness in rolling action and produce high quality gear sets. The pinions and gears are lapped in pairs and
must therefore remain as coordinated pairs for the rest of their lives. However, heat treatment distortion can vary
significantly. Thus, developing a lapping sequence for manufacturing requires both time and experienced
technicians who can establish lapping operating positions and sequence times to produce quality gear sets both in
terms of performance and cost. This development is generally trial and error. In this paper, the lapping process is
simulated using advanced modeling tools such as gear vectorial simulation for the tooth surfaces and path of
contact and reverse engineering to analyze the tooth contact pattern of existing gear sets under load (static
LTCA). Test gear sets are measured using a CMM prior to a special lapping cycle where the position of the gear
sets on the lapper does not change, and then re-measured after lapping in order to establish how much, and
where, material was removed. A wear constant named “wear coefficient” specific to the lapping compound
composition is then calculated. Based on the obtained wear coefficient value, an algorithm for simulating the
lapping process is presented. Gear sets lapped on the production line are used for simulation case studies.
Results show that it is possible to predict how much and where material will be removed, thereby opening the
door to better understanding of the lapping process.
ISBN: 1-55589-857-2 Pages: 16

05FTM10. Finite Element Study of the Ikona Gear Tooth Profile
Authors: J.R. Colbourne and S. Liu
The Ikona gear tooth profile is a patented non-involute tooth profile for internal gear pairs. Gears with this profile
have the following properties: the teeth are conjugate; the contact ratio is very high; there is no tip interference,
even when only a one-tooth difference between the pinion and internal gear; there is minimal backlash; and the
gears can be cut on conventional gear-cutting machines. Large reduction ratios can be achieved by a single gear
pair and a high contact ratio results in lower tooth stresses than for a similar involute gear. Plus, minimal backlash
makes the Ikona profile ideal for many applications, such as servo-drives, medical prostheses, and robots. Stress
analysis of these gears assumes that the contact force is equal at each contacting tooth pair. Finite element
results demonstrate how the number of tooth pairs in contact may increase under load. Finally, an estimate will be
presented, showing the variation of tooth force between the contacting teeth.
ISBN: 1-55589-858-0 Pages: 9
05FTM11. Low Loss Gears

Authors: B.-R. Höhn, K. Michaelis and A. Wimmer
In most transmission systems one power loss sources is the loaded gear mesh. High losses lead to high energy
consumption, high temperatures, early oil ageing, increased failure risk and high cooling requirements. In many
cases high efficiency is not the main focus and design criteria as load capacity or vibration excitation predominate
the gear shape design. Those design criteria can counteract high efficiency. The influences of gear geometry
parameters on gear efficiency, load capacity, and excitation are shown. Design preference guidelines can be
followed to a varying extent which leads to more or less unconventional, but more efficient gear design. Low loss
gears can save substantial energy in comparison to conventional gears. The power loss reduction is dependent
on the operating conditions and can add up to 70% of the power loss of conventional gears. Such low loss gears
have significant advantages in terms of energy consumption, heat development, and cooling requirements.
ISBN: 1-55589-859-9 Pages: 11
05FTM12. Modal Failure Analysis of a Gear and Drive Ring Assembly

Author: D.D. Behlke
After years of successful reliable applications, a component failure on a new application cannot be explained with
static stress analyses; modal failure analyses may be required. Finite element modal analyses were used to
identify the mode and its frequency that cause a high range gear and drive ring assembly to fail prematurely. A
Campbell Diagram was used to identify modes in the operating range of a six-speed transmission that could
cause the drive ring to fail. Redesigning the assembly to move the critical modes out of the operating range is
described.
ISBN: 1-55589-860-2 Pages: 8
05FTM13. Evaluation of the Scuffing Resistance of Isotropic Superfinished Precision Gears

Authors: P.W. Niskanen, B. Hansen and L. Winkelmann
Aerospace gears are often engineered to operate near the upper bounds of their theoretical design allowables.
Due to this, scuffing is a primary failure mode for aerospace gears. Isotropic superfinishing improved
Rolling/Sliding Contact Fatigue up to nine times that of baseline test specimens. Tests demonstrated the ability to
successfully carry 30 percent higher loads for at least three times the life of the baseline samples. A study was
conducted on actual gears having an isotropic superfinish. This study showed superfinishing technology increased
a gear's resistance to contact fatigue by a factor of three, and increased bending fatigue resistance by at least 10
percent. The paper discusses an additional study which is underway to determine the scuffing resistance of
isotropic superfinished aerospace gears to that of baseline ground gears. These tests were conducted using a
method that progressively increases lubricant temperature until scuffing occurs, rather than the traditional load
increasing method used in FZG testing rigs. The results of the current testing reveals that isotropic superfinished
SAE 9310 specimens show at least a 40 F higher lubricant temperature at the point of scuffing compared to as-
ground baseline gears.
ISBN: 1-55589-861-0 Pages: 10
05FTM14. Determining the Shaper Cut Helical Gear Fillet Profile

Author: G. Lian
This paper describes a root fillet form calculating method for a helical gear generated with a shaper cutter. The
shaper cutter considered has an involute main profile and elliptical cutter edge in the transverse plane. Since the
fillet profile cannot be determined with closed form equations, a Newton's approximation method was used in the
calculation procedure. The paper will also explore the feasibility of using a shaper tool algorithm for approximating
a hobbed fillet form. Finally, the paper will also discuss some of the applications of fillet form calculation
procedures such as form diameter (start of involute) calculation and finishing stock analysis.
ISBN: 1-55589-862-9 Pages: 16

05FTM15. Repair of Helicopter Gears
Authors: S. Rao, D. McPherson and G. Sroka,
In order to reduce costs by extending the operational life of the sun and input pinion gears of a helicopter
transmission, scraped gears were subject to a superfinishing process. This process was found to remove minor
foreign object damage by uniformly removing a minimal amount of material on the gear teeth, while meeting
original manufacturing specifications for geometry. The process also resulted in enhanced surface quality and did
not exhibit detrimental metallurgical effects on the surface or sub-surface of the teeth. The process was also found
to eliminate gray staining, an early precursor to pitting. This paper describes the results of the helicopter gear
repair project and includes the geometry and metallurgical evaluations on the repaired gear. Further effort to
characterize the durability and strength characteristics of the repaired gear is ongoing.
ISBN: 1-55589-863-7 Pages: 9
05FTM16. CH47D Engine Transmission Input Pinion Seeded Fault Test

Authors: J.P. Petrella, J.S. Kachelries and S.M. Holder, and T.E. Neupert
This paper summarizes an Engine Transmission Input Pinion Seeded Fault Test that was accomplished as a
portion of the validation process for the Transmission Vibration Diagnostic System (TVDS) Analyzer. The test
specimen was a high speed engine transmission input pinion with a known defect (i.e., seeded fault) machined
into a high stress area of a gear tooth root. During the testing, the TVDS analyzer monitored the test pinion real
time to provide a sufficient warning time of the impending failure. The TVDS data was evaluated along with a post-
test evaluation of the fatigue crack. During the post-test fractographic evaluation, arrest lines and fatigue striations
were analyzed to develop crack propagation data as a function of the number of applied load cycles. This data
was then correlated to better understand the potential warning signals the TVDS system could provide that would
allow the pilot enough time to unload the suspect engine transmission.
ISBN: 1-55589-864-5 Pages: 11
05FTM17. Influences of Bearing Life Considerations on Gear Drive Design

Author: F.C. Uherek
Historically, catalog gear drives have been designed with 5000 hours of L10 bearing life at service factor 1.0
power. Advances in bearing analysis methods have brought new considerations to the design and selection
process. The impact of new modeling techniques, additional considerations, and various extensions to the
traditional bearing fatigue calculations are explored. The modeling of these various additions to a traditional
catalog L10 calculation is illustrated by bearing selections for cases of single, double, and triple reduction gear
drives. A roadmap is presented listing critical considerations when applying various bearing manufacturer
recommendations.
ISBN: 1-55589-865-3 Pages: 13
05FTM18. Planet Pac: Increasing Epicyclic Power Density and Performance through Integration
Author: D.R. Lucas
Epicyclical gear systems are typically equipped with straddle-mounted planetary idlers and are supported by pins
on the input and output sides of a carrier. These carriers can be either one-piece or two-piece carrier designs.
Traditionally many of the higher power rated epicyclic gear systems use cylindrical roller bearings to support the
planetary gears. This paper will demonstrate that using a preloaded taper roller bearing in an integrated package
should be the preferred choice for this application to increase the bearing capacity, power density, and fatigue life
performance. Based on DIN281-4 calculations, this patented, fully integrated solution allows for calculated bearing
fatigue lives to be 5 times greater than a non-integrated solution and more than 1.5 times greater than a semi-
integrated solution, without changing the planet gear envelope.
ISBN: 1-55589-866-1 Pages: 7
05FTM19. The Application of Very Large, Weld Fabricated, Carburized, Hardened & Hard Finished Advanced
Technology Gears in Steel Mill Gear Drives
Authors: R.J. Drago, R. Cunningham and S. Cymbala
In the 1980's, Advanced Technology Gear (ATG) steel rolling mill gear drives consisting of carburized pinions in
mesh with very large, weld fabricated, high through hardened gears were introduced to improve capacity.
Recently, even the improvements obtained from these ATG gear sets were not sufficient to meet higher
production rates and rolling loads. For greater load capacity ATG sets have been developed consisting of
carburized, hardened pinions in mesh with very large, weld fabricated, carburized and hard finished gears. Single
and double helical gears of this type, ranging in size from 80 to 136 inches pitch diameter have been implemented
in several steel rolling applications. This paper describes the conditions that require the use of these gears and
the technology required to design, manufacture, and, especially, heat treat, these very special, very large gear
sets.
ISBN: 1-55589-867-0 Pages: 16

05FTM20. Dual Drive Conveyor Speed Reducer Failure Analysis
Author: M. Konruff
With increasing requirements, many conveyor systems utilize dual drive arrangements to increase output. Dual
drives can provide an economical solution by utilizing smaller, more efficient, system designs. However, multiple
drive conveyors must proportion the load between drives and load sharing without some type of control is difficult
to achieve. This paper presents a case study on a failure analysis of a coal mine dual drive conveyor system that
experienced gear reducer failures between 2 to 18months. Physical and metallurgical inspection of failed gearing
did not indicate material or workmanship defects, but indicated overload. In order to determine the cause of the
failures, strain gage load testing was performed. The testing of the conveyor drives revealed load sharing
problems which that will be reviewed.
ISBN: 1-55589-868-8 Pages: 9
2004 PAPERS
04FTM1. Gear Noise – Challenge and Success Based on Optimized Gear Geometries
Authors: F. Hoppe and B. Pinnekamp
Airborne and structure borne noise behavior becomes more and more an important feature for industrial
applications. Noise excitation requirements may differ with applications. Industrial conveyor belts or cement mills
are less sensitive with respect to noise emission than military applications, such as navy ship propulsion. This
paper describes requirements and solutions with regard to noise behavior focusing on examples taken from wind
turbine gear transmissions and navy applications. The individual approaches have to be a suitable compromise to
meet the challenge of noise requirement and cost optimization without restrictions on gear load carrying capacity.
Therefore, the paper shows requirements and measurements examples from shop and field tests in comparison
to gear micro geometry and calculation results.
ISBN: 1-55589-824-6 Pages: 15
04FTM2. Noise Optimized Modifications: Renaissance of the Generating Grinders?

Author: H. Geiser
While load and stress optimized tooth modifications may be normal in production, noise and vibration optimized
tooth modifications need higher production accuracies and more complex modifications than with crowning and
root or tip relief. Topological modifications show advantages for low noise and vibration behavior due to the higher
variability in direction of contact pattern. Unfortunately, a load optimized tooth flank modification is not always a
noise optimized modification—a compromise between optimized load distribution and low noise has to be found.
In a practical example the calculation possibilities will be demonstrated on how an optimized tooth modification
can be found. To satisfy the new requirements the gear grinder manufacturers needed to improve their machines.
This improvement was possible with the substitution for the mechanical transmissions in the grinder with the
modern CNC controls. By introducing a torque motor as the main table drive of a grinder, together with the direct
mounted encoder, an advantage is offered in comparison to the mechanical drive. Problems like worm gear wear,
backlash and deviations are eliminated. This, and the possibility of topological modifications, could now lead to a
renascence of the generating grinders.
ISBN: 1-55589-825-4 Pages: 9
04FTM3. A Method to Define Profile Modification of Spur Gear and Minimize the Transmission Error
Authors: M. Beghini, F. Presicce, and C. Santus
The object of this presentation is to propose a simple method to reduce the transmission error for a given spur
gear set, at a nominal torque, by means of profile modification parameters. Iterative simulations with advanced
software are needed. A hybrid method has been used, combining the finite element technique with semi analytical
solutions. A two dimensional analysis is thought to be adequate for this kind of work; in fact, the resulting software
does not require much time for model definition and simulations, with very high precision in the results. The
starting configuration is presented. At each subsequent step, little alteration of one parameter is introduced, and
the best improvement in terms of static transmission error is followed, until a minimum peak-to-peak value is
achieved. At the end a check is needed to verify that the tip relief is enough to avoid the non-conjugate contact on
the tip corner for a smooth transfer load.
ISBN: 1-55589-826-2 Pages: 11
04FTM4. Influence of Surface Roughness on Gear Pitting Behavior

Authors: T.C. Jao, M.T. Devlin, J.L. Milner, R.N. Iyer, and M.R. Hoeprich
In earlier studies, surface roughness had been shown to have a significant influence on gear pitting life. Within a
relatively small range of surface roughness (Ra = 0.1–0.3 micron), gear pitting life as measured by the FZG pitting
test decreases as the gear surface roughness increases. This inverse relationship between gear surface
roughness and pitting life is well understood in the field. To determine whether this inverse relationship is
applicable to a wider range of surface roughness values, a pitting study was conducted using gears whose
surface roughness ranges from 0.1–0.6 micron. The results were not completely expected. The study showed that
the micropitting area is radically expanded when the gear surface roughness is close to the upper limit of the

range studied. At the same time, the formation of macropitting is also greatly delayed. Not only is the pitting life
significantly longer, but the initiation of macropitting can occur near or slightly beyond the pitch line. The paper
discusses how high surface roughness introduces a wear mechanism that delays the formation of macropits.
ISBN: 1-55589-827-0 Pages: 12
04FTM5. Investigations on the Micropitting Load Capacity of Case Carburized Gears

Authors: B.-R. Höhn, P. Oster, U. Schrade and T. Tobie
Micropitting is fatigue damage that is frequently observed on case carburized gears. It is controlled by conditions
of the tribological system of tooth flank surface and lubricant. The oil film thickness has been found to be a
dominant parameter. Based on the results of investigations a calculation method to evaluate the risk of
micropitting respectively to determine a safety factor for micropitting on case carburized gears was developed.
The calculation method is based on the result of the micropitting test as a lubricant tribological parameter, but
enables the gear designer to take major influences such as operating conditions, gear geometry and gear size of
the actual application into consideration. The paper summarizes important results of the continuous experimental
investigations and introduces the proposed calculation method for rating the micropitting load capacity of case
carburized gears.
ISBN: 1-55589-828-9 Pages: 15
04FTM6. The Effect of a ZnDTP Anti-Wear Additive on Micropitting Resistance of Carburized Steel Rollers
Authors: C. Benyajati and A.V. Olver
Zinc di-alkyl dithio-phosphate (ZnDTP) compounds are widely used in engine and transmission oils both as anti-
oxidants and as anti-wear additives. However, recent work has shown that many anti-wear additives appear to
have a detrimental effect on the resistance of gears and other contacting components to various types of rolling
contact fatigue, including micropitting. The paper examines the effect of a secondary C6 ZnDTP presence in low
viscosity synthetic base oil on the resistance to micropitting and wear of carburized steel rollers, using a triple-
contact disk tester. It was found that the additive caused severe micropitting and associated wear, whereas the
pure base oil did not give rise to any micropitting. It was further found that the additive was not detrimental unless
it was present during the first 100 000 cycles of the test when it was found to exert a strong effect on the
development of roughness on the counter-rollers. It is concluded that the additive is detrimental to micropitting
resistance because it retards wear-in of the contact surfaces, favoring the development of damaging fatigue
cracks. This contrast with some earlier speculation that suggested a direct chemical effect could be responsible.
ISBN: 1-55589-829-7 Pages: 10
04FTM7. A Short Procedure to Evaluate Micropitting Using the New AGMA Designed Gears
Authors: K.J. Buzdygon and A.B. Cardis
At the 1998 AGMA Fall Technical Meeting, encouraging results of a prototype micropitting test using specially
designed gears on the standard FZG test rig were reported. Additional gear sets became available from AGMA in
2000. Subsequently, several sets of these experimental AGMA test gears were used in an attempt to develop a
relatively short test procedure to evaluate micropitting. The detailed results of these tests are discussed in the
paper. The procedure involved running the test gears on the standard FZG test rig with oil circulation for 168
hours. At the end of test, the gears are rated for micropitting, weight loss, pitting, and scuffing. Five commercially
available ISO VG 320 gear oils, with performance in the FVA Procedure 54 micropitting test ranging from FLS 9-
low to FLS >10-high, were evaluated using this procedure. The degree of micropitting coverage ranged from 34%
to 7% in the new test procedure. Micropitting generally originated in the middle of the gear tooth, instead of the
root or tip. Overall, there was excellent correlation of the degree of micropitting damage between the new test
procedure and FVA Procedure 54.
ISBN: 1-55589-830-0 Pages: 8
04FTM8. Generalized Excitation of Traveling Wave Vibration in Gears

Author: P.B. Talbert
Rotation of gears under load creates dynamic loading between the gears at tooth mesh frequency and its
harmonics. The dynamic loading can excite traveling wave vibration in the gears. The strain associated with the
traveling wave vibration can be excessive and result in high cycle fatigue of the gears. Prior investigations have
examined traveling wave excitation for specific configurations, such as a sequential star system with a fixed
planetary carrier. Gear mesh excitation of traveling wave vibration can be generalized to include the following: (1)
any number of gears surrounding the center gear, (2) non-symmetric spacing of the surrounding gears, (3) non-
equal power transfer of the surrounding gears, and (4) the effect of periodic features in the center gear. A closed
form expression is developed to quantify the relative excitation of traveling wave vibration for each nodal diameter.
This expression for the relative excitation is verified using analytical finite element examples.
ISBN: 1-55589-831-9 Pages: 13

04FTM9. Design of a High Ratio, Ultra Safe, High Contact Ratio, Double Helical Compound Planetary
Transmission for Helicopter Applications
Authors: F.W. Brown, M.J. Robuck, G.K. Roddis and T.E. Beck
An ultra-safe, high ratio planetary transmission, for application as a helicopter main rotor drive, has been designed
under the sponsorship of NRTC-RITA. It is anticipated that this new planetary transmission offers improvements
relative to the current state-of-the-art including, reduced weight, reduced transmitted noise and improved fail-
safety. This paper discusses the analysis and design results for the subject planetary transmission. Fabrication
and testing of the transmission will be conducted in subsequent phases of the project. Typically, the final stage in
helicopter main rotor transmission is the most critical and usually the heaviest assembly in the drive system for
any rotary wing aircraft. The new ultra-safe, high ratio planetary transmission design utilizes a compound
planetary configuration with a 17.5:1 reduction ratio which would replace a conventional two stage simple
planetary transmission. The new design uses split-torque paths and high combined contact ratio gearing.
ISBN: 1-55589-832-7 Pages: 12
04FTM10. The Failure Investigation and Replacement of a Large Marine Gear

Authors: P. Hopkins, B. Shaw, J. Varo, and A. Kennedy
The paper presents details of a recent gearbox problem encountered on a naval ship and the final solution
bringing the ship back to full ability. The problem occurred on the main wheel of a large, high power Naval
gearbox. The investigation showed that pitting damage had developed as a result of loose side plate bolts, which
led on to bending fatigue cracking. Additional investigations and monitoring established that the damage had been
assisted by increased usage at high power levels, as well as a small number of significant overloads. Assessment
of the gearbox design was that it had been running very close to original design limits. Repairs were then carried
out to remove and arrest any damage present, and monitoring procedures were put in place to ensure no further
damage developed. Risk assessments were performed to allow the ship to continue to meet its demands. Full
repair options were then considered and replacement gear elements designed and produced to increase future
abilities and safety factors. The paper covers the discovery of the problem, failure investigation, the in-situ repair,
risk assessment of continued running, prevention of further damage, damage monitoring, the permanent repair
assessment, design, manufacture and installation of replacement gears, and trials.
ISBN: 1-55589-833-5 Pages: 11
04FTM11. Gear Lubrication as a Reliability Partner

Author: M. Holloway
Performance lubrication is quickly becoming a component of preventive, predictive, proactive and reliability based
maintenance programs. Using the best gear lubricant, coupled with system condition, monitoring and analysis,
actually reduces overall operating expenses dramatically. Various techniques such as system conditioning, oil and
equipment analysis, along with product selection and management are valuable tools which convert many
maintenance departments into reliability centers. These concepts and others are discussed in this informative
hands-on discussion which will review best maintenance practices from various companies and review how to
implement similar programs.
ISBN: 1-55589-834-3 Pages: 8
04FTM12. Improved Tooth Load Distribution in an Involute Spline Joint Using Lead Modifications Based on
Finite Element Analysis
Authors: F.W. Brown, J.D. Hayes and G.K. Roddis
Involute splines are prone to non-uniform contact loading along their length, especially in lightweight, flexible
applications such as a helicopter main rotor shaft-to-rotor hub joint. A significantly improved tooth load distribution
is achieved by applying, to the internally splined member, complex lead corrections which vary continuously along
the length of the spline. Rotor hub splines with analytically determined lead corrections were manufactured and
tested under design load conditions. A standard rotor shaft-to-hub joint, which uses a step lead correction
between splines, was also tested as a baseline. Test data indicated that the complex lead corrections resulted in a
nearly uniform contact load distribution along the length of the spline at the design torque load. The data also
showed that the load distribution for the splines with the complex lead corrections was significantly improved
relative to the baseline splines.
ISBN: 1-55589-835-1 Pages: 16
04FTM13. Superfinishing Motor Vehicle Ring and Pinion Gears

Authors: L. Winkelmann, J. Holland and R. Nanning
Today, the automotive market is focusing on “lubed for life” differentials requiring no service for the life of the
vehicle. Premature differential failure can be caused by bearing failures as well as ring and pinion failure. By super
finishing the lapped ring and pinion gear sets to a surface roughness less than 10 micro inch, lubricant, bearing
and gear lives can be significantly increased because of the concomitant elimination of wear and the temperature
spike associated with break-in. It was assumed that super finishing technology could not preserve the contact
pattern of the lapped and matched gear set. This paper discusses a mass finishing operation which overcomes
these obstacles and meets the needs of a manufacturing facility. Gear metrology, contact patterns, transmission

error and actual performance data for super finished gear sets will be presented along with the super finishing
process.
ISBN: 1-55589-836-6 Pages: 16
04FTMS1. Stress Analysis of Gear Drives Based on Boundary Element Method

Author: D. Vecchiato
The stress analysis is performed as a part of TCA (Tooth Contact Analysis) for a gear drive. Unlike the existing
approaches, the proposed one does not require application of commercial codes (like ANSYS or ABAQUS) for
derivation of contact model and determination of contact and bending stresses. The contacting model is derived
directly by using the equations of tooth surfaces determined analytically. The boundary element approach allows
to reduce substantially the number of nodes of the model. Determination of stresses caused by applied load is
obtained directly for the applied contacting model for any position of meshing. The developed approach is
illustrated by stress analysis of helical gears with modified geometry.
ISBN: 1-55589-837-8 Pages: 16
2002 PAPERS
02FTM1. The Effect of Chemically Accelerated Vibratory Finishing on Gear Metrology
Authors: L. Winklemann, M. Michaud, G. Sroka, J. Arvin and A. Manesh
Chemically accelerated vibratory finishing is a commercially proven process that is capable of isotropically
superfinishing metals to an Ra < 1.0 in. Gears have less friction, run significantly cooler and have lower noise and
vibration when this technology is applied. Scuffing, contact fatigue (pitting), and bending fatigue are also reduced
or eliminated both in laboratory testing and field trials. This paper presents studies done on aerospace Q13 spiral
bevel gears showing that the amount of metal removed to superfinish the surface is both negligible and
controllable. Media selection and metal removal monitoring procedures are described ensuring uniform surface
finishing, controllability and preservation of gear metrology.
ISBN: 1-55589-801-7 Pages: 18
02FTM2. Development and Application of Computer-Aided Design and Tooth Contact Analysis of Spiral-Type
Gears with Cylindrical Worm
Authors: V.I. Goldfarb and E.S. Trubachov
This paper presents the method of step-by-step computer-aided design of spiroid-type gears, which involves gear
scheme design, geometric calculation of gearing, drive design, calculation of machine settings and tooth-contact
analysis. Models of operating and generating gearing have been developed, including models of manufacture and
assembly errors, force and temperature deformations acting in real gearing, and drive element wear. Possibilities
of CAD-technique application are shown to solve design and manufacture tasks for gearboxes and gear-motors
with spiroid-type gears.
ISBN: 1-55589-802-5 Pages: 15
02FTM3. The Application of Statistical Stability and Capability for Gear Cutting Machine Acceptance Criteria
Author: T.J. Maiuri
Over the years the criteria for gear cutting machine acceptance has changed. In the past, cutting a standard test
gear or cutting a customer gear to their specification was all that was expected for machine acceptance. Today,
statistical process control (SPC) is required for virtually every machine runoff. This paper will cover the basic
theory of stability and capability and its application to bevel and cylindrical gear cutting machine acceptance
criteria. Actual case studies will be presented to demonstrate the utilization of these SPC techniques.
ISBN: 1-55589-803-3 Pages: 26
02FTM4. Multibody-System-Simulation of Drive Trains of Wind Turbines

Author: B. Schlecht
During the last years a multitude of wind turbines have been put into operation with continuously increased power
output. Wind turbines with 6 MW output are in the stage of development, a simple extrapolation to larger
dimensions of wind turbines on the basis of existing plants and operational experiences is questionable. This
paper deals with the simulation of the dynamic behavior of the complete drive train of a wind turbine by using a
detailed Multi-System-Model with special respect of the gear box internals. Starting with the model creation and
the analysis of the natural frequencies, various load cases in the time domain will be discussed.
ISBN: 1-55589-804-1 Pages: 13

02FTM5. Crack Length and Depth Determination in an Integrated Carburized Gear/Bearing
Authors: R. Drago and J. Kachelries
In an effort to determine if processing cracks posed a safety of flight concern, several gears that contained cracks
were designated to undergo a rigorous bench test. Prior to the start of the test, it was necessary to document,
nondestructively, all of the crack dimensions. This paper will present a specially modified magnetic rubber
inspection technique to determine crack lengths as short as 0.006 inch, and a unique, highly sensitive, laboratory
eddy current inspection technique to estimate crack depths up to +/– 0.003 inch.
ISBN: 1-55589-805-2 Pages: 9
02FTM6. Contemporary Gear Hobbing – Tools and Process Strategies

Author: C. Kobialka
Gear manufacturing without coolant lubrication is getting more and more important. Modern hobbing machines are
designed to cope with dry hobbing. In the last years, carbide hobs were prevailing in high-speed hobbing due to
their excellent thermal stability. Today, this high performance rate is confronted with rather high tool costs and
critical tool handling. Powder metallurgical HSS combined with extremely wear resistant coating on the base of
(Ti, Al) N offer interesting alternatives for dry hobbing. It is evident that existing conventional hob geometries can
be optimized respecting limiting factors like maximum chip thickness and maximum depth of scallops.
ISBN: 1-55589-806-8 Pages: 11
02FTM7. Selecting the Best Carburizing Method for the Heat Treatment of Gears
Authors: D. Herring, G. Lindell, D. Breuer and B. Madlock
Vacuum carburizing has proven itself a robust heat treatment process and a viable alternative to atmosphere
carburizing. This paper will present scientific data in support of this choice. A comparison of atmosphere
carburized gears requiring press quenching to achieve dimensional tolerances in a “one piece at a time” heat
treating operation, with a vacuum carburized processing a full load of gears that have been high gas pressure
quenched within required tolerances.
ISBN: 1-55589-807-6 Pages: 13
02FTM8. Compliant Spindle in Lapping and Testing Machines

Author: B. McGlasson
This paper presents theory, analysis and results of a novel spindle design with application to bevel gear lapping
and testing machines. The spindle design includes a rotationally compliant element which can substantially
reduce the dynamic forces induced between the gear members while rolling under load. The theory of this spindle
concept is presented using simplified models, providing the explanation for the process benefits it brings. Analysis
and simulations give additional insight into the dynamics of the system. Finally, actual lapping and testing machine
results are presented.
ISBN: 1-55589-808-4 Pages: 11
02FTM9. Gear RollScan for High Speed Gear Measurement

Author: A. Pommer
This presentation features a revolutionary new method for the complete topographical measurement of gears. The
Gear RollScan system is similar to one-flank gear rolling inspection. However, the master gear has measuring
tracks on selected flanks. With two master gears in roll contact, both the left and right flanks of the specimen can
be inspected simultaneously. After a specified number of rotations, every measuring track on the master gears will
contact every flank of the specimen this measuring device will always find the worst tooth.
ISBN: 1-55589-809-2 Pages: 10
02FTM10. Comparing the Gear Ratings from ISO and AGMA

Author: O. LaBath
In the early 1980's several technical papers were given comparing gear ratings from ISO and AGMA showing
some interesting and diverse differences in the trends when the gear geometry was changed slightly. These
changes included addendum modification coefficients and helix angle. Differences also existed when the
hardness and hardening methods were changed. This paper will use rating programs developed by an AGMA
committee to compare AGMA and ISO ratings while having the same gear geometry for both ratings. This will
allow consistent trend analysis by only changing one gear geometry parameter while holding other geometry
items constant.
ISBN: 1-55589-810-6 Pages: 17

02FTM11. Gear Design Optimization Procedure that Identifies Robust, Minimum Stress and Minimum Noise
Gear Pair Designs
Author: D. Houser
Typical gear design procedures are based on an iterative process that uses rather basic formulas to predict
stresses. Modifications such as tip relief and lead crowning are based on experience and these modifications are
usually selected after the design has been considered. In this process, noise is usually an afterthought left to be
chosen by the designer after the geometric design has been established. This paper starts with micro-
topographies in the form of profile and lead modifications. Then, evaluations are made on the load distribution,
bending and contact stresses, transmission error, film thickness, flash temperature, etc. for a large number of
designs. The key to this analysis is the rapid evaluation of the load distribution.
ISBN: 1-55589-811-4 Pages: 15
02FTMS1 Design and Stress Analysis of New Version of Novikov-Wildhaber Helical Gears
Author: I. Gonzalez-Perez
This paper covers design, generation, tooth contact analysis and stress analysis of a new type of Novikov-
Wildhaber helical gear drive. Great advantages of the developed gear drive in comparison with the previous ones
will be discussed, including: reduction of noise and vibration caused by errors of alignment, the possibility of
grinding, and application of hardened materials and reduction of stresses. These achievements are obtained by
application of: new geometry based on application of parabolic rack-cutters, double-crowning of pinion and
parabolic type of transmission errors.
ISBN: 1-55589-812-2 Pages: 25
2001 PAPERS
01FTM1. Carbide Hobbing Case Study
Author: Y. Kotlyar
Carbide hobbing improves productivity and cost, however many questions remain regarding the best application,
carbide material, hob sharpening, coating and re-coating, hob handling, consistency and optimum hob wear, best
cutting conditions, and concerns for the initial cutting tool investment. This paper is a case study of a successful
implementation of carbide hobbing for an annual output of 250,000 gears, average lot size of about 200–300
gears, producing gears of about 150 different sizes and pitches, with 4 setups per day on average.
ISBN: 1-55589-780-0 Pages: 16
01FTM2. The Ultimate Motion Graph for “Noiseless” Gears

Authors: H.J. Stadtfeld and U. Geiser
Gear noise is a common problem in all bevel and hypoid gear drives. A variety of expensive gear geometry
optimizations are applied daily in all hypoid gear manufacturing plants, to reduce gear noise. In many cases those
efforts have little success. This paper will present “The Ultimate Motion Graph,” a concept for modulating the tooth
surfaces that uses modifications to cancel operating dynamic disturbances that are typically generated by any
gear types.
ISBN: 1-55589-781-9 Pages: 16
01FTM3. Automated Spiral Bevel Gear Pattern Inspection

Authors: S.T. Nguyen, A. Manesh, K. Duckworth and S. Wiener
Manufacturing processes for precision spiral bevel gears are operator intensive, making them particularly costly in
today's small lot production environment. This problem is compounded by production requirements for
replacement parts that have not been produced for many years. The paper will introduce a new closed loop
system capable of reducing development costs by 90% and bevel gear grinder setup time by 80%. In addition, a
capability to produce non-standard designs without part data summaries is reviewed. Advancements will also be
presented for accepting precision gears using an electronic digital master in lieu of a physical master.
ISBN: 1-55589-782-7 Pages: 15
01FTM4. How to Inspect Large Cylindrical Gears with an Outside Diameter of More Than 40 Inches
Author: G. Mikoleizig
This paper discusses the design and function of the relevant machines used for individual error measurements
such as lead and profile form as well as gear pitch and runout. The author will cover different types of inspection
machines such as: stationary, CNC-controlled gear measuring centers, and transportable equipment for checking
individual parameters directly on the gear cutting or gear grinding machine.
ISBN: 1-55589-783-5 Pages: 20

01FTM5. Traceability of Gears – New Ideas, Recent Developments
Authors: F. Härtig and F. Wäldele
Some national standard tolerances for cylindrical gears lie in, and even below, the range of instrument
measurement uncertainties. This paper presents a concept based on three fundamental goals: reduction of
measurement uncertainty, construction of work piece-like standards, and shortening of the traceability chain. One
of the focal points is the development of a standard measuring device as an additional metrological frame
integrated into a coordinate measuring machine.
ISBN: 1-55589-784-3 Pages: 6
01FTM6. Performance-Based Gear-Error Inspection, Specification, and Manufacturing-Source Diagnostics

Authors: W.D. Mark and C.P. Reagor
This paper will show that a frequency-domain approach for the specification of gear tooth tolerance limits is
related to gear performance and transmission errors. In addition, it is shown that one can compute, from detailed
tooth measurements, the specific tooth error contributions that cause any particularly troublesome rotational
harmonic contributions to transmission error, thereby permitting manufacturing source identification of
troublesome operation.
ISBN: 1-55589-785-1 Pages: 15
01FTM7. Chemically Accelerated Vibratory Finishing for the Elimination of Wear and Pitting of Alloy
Steel Gears
Authors: M. Michaud, G. Sroka and L. Winkelmann
Chemically accelerated vibratory finishing eliminates wear and contact fatigue, resulting in gears surviving higher
power densities for a longer life compared to traditional finishes. Studies have confirmed this process is
metallurgically safe for both through hardened and case carburized alloy steels. The superfinish can achieve an
Ra < 1.5 μinch, while maintaining tolerance levels. Metrology, topography, scanning electron microscopy,
hydrogen embrittlement, contact fatigue, and lubrication results are presented.
ISBN: 1-55589-786-4 Pages: 16
01FTM8. The Effect of Spacing Errors and Runout on Transverse Load Sharing and the Dynamic Factor of
Spur and Helical Gears
Authors: H. Wijaya, D.R. Houser and J. Harianto
This paper addresses the effect of two common manufacturing errors on the performance of spur and helical
gears; spacing error and gear runout. In spacing error analysis, load sharing for two worst-case scenarios are
treated, one where a tooth is out of position and the second where stepped index errors are applied. The analyzed
results are then used as inputs to predict gear dynamic loads, dynamic tooth stresses and dynamic factors for
gear rating.
ISBN: 1-55589-787-8 Pages: 16
01FTM9. New Opportunities with Molded Gears

Authors: R.E. Kleiss, A.L. Kapelevich and N.J. Kleiss Jr.
Unique tooth geometry that might be difficult or even impossible to achieve with cut gears can be applied to
molded gears. This paper will investigate two types of gears that have been designed, molded and tested in
plastic. The first is an asymmetric mesh with dissimilar 23 and 35-degree pressure angles. The second is an
orbiting transmission with a 65-degree pressure angle. Both transmissions have higher load potential than
traditional design approaches.
ISBN: 1-55589-788-6 Pages: 11
01FTM10. Design Technologies of High Speed Gear Transmission

Author: J. Wang
This paper discusses a few critical factors and their effects on high speed gear transmissions. The first factor is
centrifugal force and its effect on tooth root strength, tooth expansion and backlash and the interference fit
between gear and shaft. The second is system dynamics, including critical speed, dynamic balancing and the
torsional effects of flexible couplings. The third is the windage loss with different combinations of helix and rotation
direction, lubricant flow rate, flow distribution and their effects on tooth bulk temperature field and tooth thermal
expansion.
ISBN: 1-55589-789-4 Pages: 8

01FTM11. Kinematic and Force Analysis of a Spur Gear System with Separation of Sliding and Rolling
between Meshing Profiles
Author: D.E. Tananko
This paper describes a comprehensive study of the novel gear design with physical separation between sliding
and rolling motions of the mesh gear contact point. The sliding motion is accommodated by shear deformation of
a thin-layered rubber-metal laminate allowing very high compression loads. Several important advantages will be
presented when comparing the composite gear design to the conventional involute profile.
ISBN: 1-55589-790-8 Pages: 50
01FTMS1. Optical Technique for Gear Contouring

Author: F. Sciammarella
This paper presents an optical technique (projection moiré) that is compact and can provide a quick full field
analysis of high precision gears. Comparisons are made between mechanical and optical profiles obtained of a
gear tooth.
ISBN: 1-55589-791-6 Pages: 12

Index of AGMA Withdrawn Standards and Information Sheets
Document # Year Published Replaced by or Incorporated into History Tree
AGMA 110.04 1979 ANSI/AGMA 1010-E95 Figure 5
AGMA 111.03 1954 AGMA 112.04 Figure 6
AGMA 112.05 1976 ANSI/AGMA 1012-F90 Figure 6
AGMA 113.01 1952 Withdrawn without replacement --
AGMA 114.02 1973 AGMA 910-C90 Figure 4
AGMA 115.01 1959 AGMA 933-B03 --
AGMA 118.01 1973 AGMA 906-A94 --
AGMA 120.01 1975 ANSI/AGMA 1102-A03 Figure 7
AGMA 121.02 1956 AGMA 120.01 Figure 7
AGMA 122.02 1956 AGMA 120.01 Figure 7
AGMA 123.01 1956 AGMA 120.01 Figure 7
AGMA 124.01 1957 AGMA 120.01 Figure 7
AGMA 150.03 1968 AGMA 460.05 Figure 3
AGMA 151.02 1963 AGMA 420.04 Figure 3
AGMA 152.02 1960 AGMA 420.04 Figure 3
AGMA 170.01 1976 ANSI/AGMA 6002-B93 Figure 10
AGMA 203.03 1973 AGMA 916-A19 --
AGMA 206.03 AGMA 208.02 Figure 19
AGMA 207.06 1977 ANSI/AGMA 1003-G93 Figure 4
AGMA 210.02 1965 AGMA 218.01 Figure 2
AGMA 211.02 1969 AGMA 218.01 Figure 2
AGMA 211.02A 1966 AGMA 420.04 Figure 3
AGMA 211.02B AGMA 460.05 Figure 3
AGMA 215.01 1966 AGMA 218.01 & ANSI/AGMA 2003-B97 Figure 2

AGMA 218.01 1982 ANSI/AGMA 2001-B88 & AGMA 908-B89 Figure 2
AGMA 220.02 1966 AGMA 218.01 Figure 2
AGMA 221.02 1965 AGMA 218.01 Figure 2
AGMA 221.02B 1963 AGMA 440.05 Figure 3
AGMA 221.02C 1965 Withdrawn without replacement --
AGMA 221.02D 1966 Withdrawn without replacement --
AGMA 222.02 1964 AGMA 226.01 & ANSI/AGMA 2003-A86 Figure 2
AGMA 223.01B AGMA 460.05 Figure 3
AGMA 225.01 1967 AGMA 226.01 Figure 2
AGMA 226.01 1970 AGMA 908-B89 Figure 2
AGMA 229.07 Withdrawn without replacement Figure 2
AGMA 231.52 1966 ANSI/AGMA 2002-B88 --
AGMA 234.01 1956 AGMA 390.02 Figure 1
AGMA 235.02 1964 AGMA 390.03 Figure 1
AGMA 236.04 1956 AGMA 390.03 Figure 1
AGMA 237.01 1964 AGMA 390.03 Figure 1
AGMA 239.01 1965 AGMA 390.03 Figure 1
AGMA 241.02 1965 AGMA 240.01 Figure 8
AGMA 242.02 1946 AGMA 240.01 Figure 8
AGMA 243.01 1954 AGMA 240.01 Figure 8
AGMA 243.61 1964 AGMA 240.01 Figure 8
AGMA 243.71 1964 AGMA 240.01 Figure 8
AGMA 244.01 1959 AGMA 240.01 Figure 8
AGMA 245.01 1964 AGMA 240.01 Figure 8
AGMA 246.02A 1983 Replaced by 926-C99 --
AGMA 247.01 1965 AGMA 240.01 Figure 8
AGMA 248.01 1964 AGMA 240.01 Figure 8
AGMA 249.01 1964 AGMA 240.01 Figure 8
AGMA 250.02a 1956 AGMA 250.03 Figure 17

AGMA 250.04 1981 ANSI/AGMA 9005-D94 Figure 17
AGMA 251.02 1974 ANSI/AGMA 9005-D94 Figure 17
AGMA 252.01 1959 AGMA 250.03 Figure 17
AGMA 254.01 1955 AGMA 250.04 Figure 17
AGMA 254.04 1944 AGMA 251.02 Figure 17
AGMA 255.02 1964 AGMA 260.02 Figure 9
AGMA 260.02 1974 ANSI/AGMA 6001-C88 Figure 9
AGMA 265.01 1953 AGMA 260.02 Figure 9
AGMA 271.03 1963 AGMA 420.04 Figure 3
AGMA 291.01 1962 AGMA 420.04 Figure 3
AGMA 295.04 1977 AGMA 297.02 Figure 13
AGMA 298.01 1975 AGMA 297.02 Figure 13
AGMA 299.01 1987 AGMA 914-A04 --
AGMA 323.01 1969 ANSI/AGMA 6005-B89 --
AGMA 331.01 1969 ANSI/AGMA 2008-B90 --
AGMA 370.01 1973 AGMA 917-B97 --
AGMA 390.03 1980 AGMA 390.03a & ANSI/AGMA 2000-A88 Figure 1
AGMA 390.03a ANSI/AGMA 2009-A98, ANSI/AGMA Figure 1
1980
2011-A98 & ANSI/AGMA 2111-A98
AGMA 411.02 1966 AGMA 911-A94 --
AGMA 420.04 ANSI/AGMA 6010-E88, ANSI/AGMA Figure 3
1975
6023-A88, & ANSI/AGMA 6123-A88
AGMA 423.01 1963 AGMA 420.04 Figure 3
AGMA 425.01 1965 AGMA 420.04 Figure 3
AGMA 426.01 1972 ANSI/AGMA 6000-A88 --
AGMA 427.01 1976 ANSI/AGMA 6011-H98 Figure 11
AGMA 430.03 1963 AGMA 420.04 Figure 3

AGMA 431.01 1964 AGMA 937-A12 --
AGMA 481.01 1971 Incorporated into 6021-G89 Figure 3
AGMA 510.03 1984 ANSI/AGMA 9009-D02 --
AGMA 514.02 1971 AGMA 922-A96 --
AGMA 515.02 1977 ANSI/AGMA 9000-C90 --
AGMA 516.01 1978 ANSI/AGMA 9008-B00 --
AGMA 600.01 1979 AGMA 904-B89 --
AGMA 906-A94 1994 Withdrawn without replacement --
AGMA 912-A04 2004 ANSI/AGMA 1010-F14 Figure 5
AGMA 915-1-A02 2002 AGMA ISO 10064-1-A21 Figure 1
AGMA 921-A97 1997 ANSI/AGMA 6006-A03 --
AGMA 931-A02 2002 AGMA ISO 10064-5-A06 Figure 20
AGMA 2000-A88 AGMA 915-1-A02, AGMA 915-2-A05, Figure 1
1988 AGMA 915-3-A99, ANSI/AGMA 2015-1-
A01, & ANSI/AGMA 2015-2-A06
ANSI/AGMA 2005-D03 AGMA ISO 22849-A12 & ANSI/AGMA Figure 19
1988
ISO 23509-A08
ANSI/AGMA 2007-C00 2000 ANSI/AGMA 14104-A17 Figure 18
ANSI/AGMA 2009-B01 AGMA ISO 10064-6-A10 & ANSI/AGMA Figure 1
2001
ISO 17485-A08
ANSI/AGMA 2010-A94 1994 AGMA ISO 10064-5-A06 & ANSI/AGMA Figure 20
ISO 18653-A06
ANSI/AGMA 2015-1-A01 2001 ANSI/AGMA ISO 1328-1-B14 Figure 1
ANSI/AGMA 2015-2-B15 2015 ANSI/AGMA ISO 1328-2-A21 Figure 1
Supplemental Tables for 2002 ANSI/AGMA ISO 1328-1-B14 --
AGMA 2015/915-1-A02
ISO 18653-A06
ISO 18653-A06

ISO 18653-A06
ANSI/AGMA 6004-F88 1988 ANSI/AGMA 6014-A06 Figure 12
ANSI/AGMA 6005-B89 1989 ANSI/AGMA 6015-A13 & ANSI/AGMA --
6115-A13
ANSI/AGMA 6009-A00 2000 ANSI/AGMA 6013-A06 Figure 3
ANSI/AGMA 6017-E86 1989 ANSI/AGMA 6035-A02 & ANSI/AGMA Figure 15
6135-A02
ANSI/AGMA 6019-E89 1989 ANSI/AGMA 6009-A00 & ANSI/AGMA Figure 3
6019-A00
ANSI/AGMA 6021-G89 1989 ANSI/AGMA 6009-A00 & ANSI/AGMA Figure 3
6019-A00
ANSI/AGMA 6023-A88 1988 ANSI/AGMA 6123-B06 Figure 3
ANSI/AGMA 6030-C87 1987 ANSI/AGMA 6035-A02 & ANSI/AGMA Figure 15
6135-A02
ANSI/AGMA 6109-A00 2000 ANSI/AGMA 6113-A06 Figure 3

Notes:
• Red text boxes denote withdrawn documents
• Blue text boxes denote current documents
Figure 1 – Inspection Documents

Notes:
• Red text boxes denote
withdrawn documents
• Blue text boxes denote
current documents
Figure 2 – Rating Documents

Notes:
• Red text boxes denote
withdrawn documents
• Blue text boxes denote
current documents
Figure 3 – Enclosed Gear Drives Design Documents

Notes:
Figure 4 – Fine Pitch Documents

Notes:
Figure 5 – Terminology of Wear and Failure Documents

Notes:
Figure 6 – Nomenclature Documents

Notes:
Figure 7 – Hob Documents

Notes:
Figure 8 – Gear Materials and Heat Treatment Processing Manual Documents

Notes:
Figure 9 – Design and Selection of Components for Enclosed Gear Drives Documents

Notes:
Figure 10 – Vehicle Gearing Documents

Notes:
Figure 11 – Specification for High Speed Gear Units Documents

Notes:
Figure 12 – Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment Documents

Notes:
Figure 13 – Sound for Enclosed Helical Herringbone and Spiral Bevel Gear Drives Documents

Notes:
Figure 14 – Practice for Enclosed Cylindrical Wormgear Speed Reducers and Gearmotors Documents

Notes:
Figure 15 – Wormgearing Design Documents

Notes:
Figure 16 – Bores and Keyways for Flexible Couplings (Inch Series) Documents

Notes:
Figure 17 – Gear Lubrication Documents

Notes:
Figure 18 – Surface Temper Etch Inspection Documents

Notes:
Figure 19 – Bevel Gear Design Documents

Notes:
Figure 20 – Gear Measuring Instruments Documents

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Technical Publications Catalog

AGMA Publications Catalog i March 2023

American Gear Manufacturers Association

Phone: (703) 684-0211

Technology Driven. Globally Connected.

AGMA Publications Catalog ii March 2023

Index of AGMA Current Standards and Information Sheets

Number Title Page

AGMA Publications Catalog 1 March 2023

AGMA Publications Catalog 2 March 2023

AGMA Publications Catalog 3 March 2023

AGMA Publications Catalog 4 March 2023

Calibration and Measurement Uncertainty

Design and Assembly – Bevel

Design – Fine Pitch

Design – Spur and Helical

AGMA Publications Catalog 5 March 2023

High Speed Units

Inspection and Tolerances

AGMA Publications Catalog 6 March 2023

Powder Metallurgy Gears

Rating: Spur, Helical and Bevel Gears

AGMA Publications Catalog 7 March 2023

Sound and Vibration

Wind Turbine Units

AGMA Publications Catalog 8 March 2023

AGMA 904-C96 Metric Usage

AGMA 905-A17 Inspection of Molded Plastic Gears

AGMA 909-A06 Specifications for Molded Plastic Gears

AGMA 910-D12 Formats for Fine-Pitch Gear Specification Data

AGMA Publications Catalog 9 March 2023

AGMA 916-A19 Face Gears with Intersecting Perpendicular Axes

AGMA 917-B97 Design Manual for Parallel Shaft Fine-Pitch Gearing

AGMA Publications Catalog 10 March 2023

AGMA 920-B15 Materials for Plastic Gears

AGMA 925-B22 Effect of Tribology and Lubrication on Gear Surface Distress

AGMA 926-C99 Recommended Practice for Carburized Aerospace Gearing

AGMA Publications Catalog 11 March 2023

AGMA 933-B03 Basic Gear Geometry

AGMA 937-A12 Aerospace Bevel Gears

AGMA 938-A05 Shot Peening of Gears

AGMA 939-A07 Austempered Ductile Iron for Gears

AGMA Publications Catalog 12 March 2023

AGMA 943-A22 Tolerances for Spur and Helical Racks

AGMA 944-A19 Mechanisms of Powder Metal, PM, Gear Failures

AGMA 945-1-B20 Splines – Design and Application

AGMA 945-2-B20 Splines – Design and Application (Inch Edition)

AGMA 946-A21 Test Methods for Plastic Gears

AGMA 955-A22 Guidance for Industrial Gear Lubrication

AGMA Publications Catalog 13 March 2023

AGMA ISO 18792-A19 Lubrication of Industrial Gear Drives

AGMA ISO 22849-A12 Design Recommendations for Bevel Gears

AGMA Publications Catalog 14 March 2023

ANSI/AGMA 1010-F14 Appearance of Gear Teeth – Terminology of Wear and Failure

ANSI/AGMA 1012-G05 Gear Nomenclature, Definitions of Terms with Symbols