METRIC THREAD DIMENSIONS CALCULATOR

Metric thread calculator to calculate external and internal metric thread dimensions including
major diameter, minor diameter, pitch diameter and thread tolerance according to ISO 724 and
ISO 965 standards.

There are two calculation options available, general engineering use or custom use.

In general engineering use, calculations can be done by selecting a standard metric thread size in a
range from 1.6 mm (M1.6) to 64 mm (M64). Tolerance class can be selected among the alternatives
6e, 6f, 6g and 4h for bolts and 5H, 6H, 7H and 6G for nuts. 6g and 6H are default values and
selected class for commercial external threads and internal threads in ISO 965-1:1998. The user
shall use 6g for bolts and 6H for nuts unless there is a specific requirement to use other tolerance
classes.

In custom use, thread size, pitch and tolerance classes can be independently selected for custom
metric thread dimensions calculations.

Some important notes from ISO metric thread standards:

- External Screw Thread Designation: Nominal Diameter x Pitch - Tolerance class for pitch diameter
- Tolerance class for major diameter (M10 x 1 5g 6g)

- Internal Screw Thread Designation: – Nominal Diameter x Pitch - Tolerance class for pitch
diameter - Tolerance class for minor diameter (M10 x 1 5H 6H)

- If the two class designations for the pitch diameter and crest diameter are the same it is not
necessary to repeat the symbols. (M10 x 1 6g)

- According to ISO 1 , standard reference temperature for geometrical product specification is 20

°C.

- Gauges and gauging for ISO general purpose metric threads are defined in the ISO 1502
standard.

- The list of metric screw thread used in general engineering applications are given in the General
Purpose Metric Screw Threads Table.
Metric Thread Calculator:

INPUT PARAMETERS

Calculatio
General Engineering Use Custom Use
n Type

GENERAL ENGINEERING USE

M1.6 x 0.35 M2 x 0.4 M2.5 x 0.45 M3 x 0.5 M4 x 0.7 M5 x 0.8 M6 x 1 M8 x 1 M8 x

Metric 1.25 M10 x 1 M10 x 1.25 M10 x 1.5 M12 x 1.25 M12 x 1.5 M12 x 1.75 M16 x 1.5 M16 x
Thread 2 M20 x 1.5 M20 x 2 M20 x 2.5 M24 x 2 M24 x 3 M30 x 2 M30 x 3.5 M36 x 3 M36 x 4
M42 x 3 M42 x 4.5 M48 x 3 M48 x 5 M56 x 4 M56 x 5.5 M64 x 4 M64 x 6

External
Thread
(Bolt) 6e 6f 6g 4h
Tolerance
Class *
Internal
Thread
(Nut) 6G 5H 6H 7H
Tolerance
Class**

CUSTOM USE

Nominal
Diameter
0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.6 0.7 0.75 0.8 1 1.25 1.5 1.75 2 2.5 3 3.5 4 4.5 5
Pitch
5.5 6 8

Bolt Tolerance Class

Tolerance Grades Deviations

Pitch
Diameter 3 4 5 6 7 8 9 e f g h
Tolerance
Major
Diameter 4 6 8 e f g h
Tolerance

Nut Tolerance Class

Tolerance Grades Deviations

Pitch
Diameter 4 5 6 7 8 G H
Tolerance
Minor
Diameter 4 5 6 7 8 G H
Tolerance

Note : * 6g is normally selected for commercial external (bolt) threads. Use this tolerance class for
commercial external (bolt) threads. For usage of the other classes, refer to ISO 965-1:1998.

Note : ** 6H is normally selected for commercial internal (nut) threads. Use this tolerance class for
commercial internal threads. For usage of the other classes, refer to ISO 965-1:1998.

RESULTS

Parameter Value

Note Calculations are done according to tolerance tables given in ISO 965-1.

Designation -- M8x1.25

Tolerance Class for Bolt -- 6e

---
Tolerance Class for Nut -- 6G

Screw Thread Series -- Coarse

Pitch P 1.25 mm

LIMITS OF SIZES FOR EXTERNAL THREADS (BOLTS)

Maximum Major Diameter dmax 7.937

Minimum Major Diameter dmin 7.725

mm
Maximum Pitch Diameter d2max 7.125

Minimum Pitch Diameter d2min 7.007

 Maximum Rounded Root
d3max 6.556
Minor Diameter
Minimum Rounded Root
d3min 6.237
Minor Diameter

Minimum Root Radii Rmin 0.156

Minimum Truncation Cmin 0.156

Maximum Truncation Cmax 0.316

LIMITS OF SIZES FOR INTERNAL THREADS (NUTS)

Minimum Major Diameter Dmin 8.028

Maximum Pitch Diameter D2max 7.376

Minimum Pitch Diameter D2min 7.216 mm

Maximum Minor Diameter D1max 6.940

Minimum Minor Diameter D1min 6.675

BASIC DIMENSIONS

Basic Major Diameter d,D 8

Basic Pitch Diameter d2 , D2 7.188

mm
Basic Minor Diameter d1, D1 6.647

Fundamental Triangle Height H 1.083000

Note-1: For coated threads, the tolerances apply to the parts before coating, unless otherwise
stated. After coating, the actual thread profile shall not at any point transgress the maximum
material limits for positions h or H. For external (bolt) threads; The actual root contours shall not at
any point transgress the basic profile. Fasteners of property class 8.8 and higher (see ISO 898-1),
the root profile shall have a non-reversing curvature, no portion of which shall have a radius of less
than Rmin.

Definitions:
Basic profile: The theoretical profile of a screw thread in an axial plane defined by theoretical
dimensions and angles common to internal and external threads

Crest: The surface at the top of the ridge connecting its two flanks.

Gauges and Gauging: Details for the manufacture and use of gauges for checking ISO general-
purpose metric screw threads are specified in the ISO 1502:1996 standard. It specifies the features
of the types of gauges (Solid/adjustable GO screw ring gauges, check plugs, setting plugs, wear
check plugs, screw caliper gauges, plug gauges, etc.) which are recommended for checking
external and internal screw threads of workplaces and for the setting and checking of certain of the
screw gauges.

Major Diameter: The maximum diameter of a thread which is diameter of the crest of a male
thread or root of a female thread.

Minor Diameter: The minimum diameter of a thread which is diameter of the root of a male
thread or crest of a female thread.

Root: The surface at the bottom of the groove connecting the adjacent flanks

Thread pitch: The distance between two adjacent threads.

Supplements:

 Thread calculators and charts

 Metric thread chart
 Metric thread profile and formulas

Reference:

 Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2016) . Machinery's Handbook . 30th
edition. Industrial Press Inc.
 ISO 1:2002 - Geometrical Product Specifications (GPS) - Standard reference temperature for
geometrical product specification and verification
 ISO 68-1:1998 (E) - ISO general purpose screw threads — Basic profile — Part 1: Metric
screw threads
 ISO 262:1998 (E) - ISO general purpose metric screw threads — Selected sizes for screws,
bolts and nuts
 ISO 724:1993 (E) - ISO general-purpose metric screw threads - Basic dimensions
 ISO 965-1:1998 – ISO General Purpose Metric Screw Threads – Tolerances Part-1: Principles
and Basic Data
 ISO 965-2:1998 – ISO General Purpose Metric Screw Threads – Tolerances Part-2: Limits of
sizes for general purpose external and internal screw threads - Medium quality
 BS 3643-1:2007 – ISO General Purpose Metric Screw Threads – Tolerances Part-1: Principles
and Basic Data (British Standard)
Not : Hesaplama tablosuna

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Taner DEMİREL
16-Mayıs-2024