HARDNESS TESTING BASICS

• Hardness is a characteristic of a material, not a fundamental physical

property. It is defined as the resistance to indentation, and it is
determined by measuring the permanent depth of the indentation.
More simply put, when using a fixed force (load)* and a given indenter,
the smaller the indentation, the harder the material. Indentation
hardness value is obtained by measuring the depth or the area of the
indentation using one of over 12 different test methods.
• Hardness testing is used for two general characterizations
• 1.Material Characteristics
• Test to check material
• Test hardenability
• Test to confirm process
• Can be used to predict Tensile strength
2. Functionality
• Test to confirm ability to function as designed.
• Wear Resistance
• Toughness
• Resistance to impact
 HARDNESS TESTING CONSIDERATIONS
• The following sample characteristics should be consider prior to selecting the
hardness testing method to use:
• Material
• Sample Size
• Thickness
• Scale
• Shape of sample, round, cylindrical, flat, irregular
• Gage R & R

• Material
The type of material and expected hardness will determine test method.
Materials such as hardened bearing steels have small grain size and can be
measured using the Rockwell scale due to the use of diamond indenters and high
PSI loading. Materials such as cast irons and powder metals will need a much
larger indenter such as used with Brinell scales. Very small parts or small sections
may need to be measured on a microhardness tester using the Vickers or Knoop
Scale.
When selecting a hardness scale, a general guide is to select the scale that
specifies the largest load and the largest indenter possible without exceeding
defined operation conditions and accounting for conditions that may influence
the test result.
• Sample Size
The smaller the part, the lighter the load required to produce the required
indentation. On small parts, it is particularly important to be sure to meet
minimum thickness requirements and properly space indentations away from
inside and outside edges. Larger parts need to be fixture properly to ensure
secure placement during the test process without the chance for movement or
slippage. Parts that either overhang the anvil or are not easily supported on
the anvil should be clamped into place or properly supported.

• Cylindrical Samples
A correction to a test result is needed when testing on cylinder shapes with
small diameters due to a difference between axial and radial material
flow. Roundness correction factors are added to your testing result based on
the diameter of convex cylinder surfaces. Additionally, it is important to
maintain a minimum spacing equal to 2~1/2 times the indentation's diameter
from an edge or another indentation.
• Sample Thickness
Your sample should have a minimal thickness that is at least 10x (ten times) the
indentation depth that is expected to be attained. There are minimum,
allowable thickness recommendations for regular and superficial Rockwell methods
• Scales
Sometimes it is necessary to test in one scale and report in another scale. Conversions
have been established that have some validity, but it is important to note that unless an
actual correlation has been completed by testing in different scales, established
conversions may or may not provide reliable information. Refer to ASTM scale conversion
charts for non-austenitic metals in the high hardness range and low hardness range. Also
refer to ASTM standard E140 for more scale conversion information.
• Gage R&R
Gage Repeatability and Reproducibility Studies were developed to calculate the ability of
operators and their instruments to test accordingly within the tolerances of a given test
piece. In hardness testing, there are inherent variables that preclude using standard Gage
R&R procedures and formulas with actual test pieces. Material variation and the inability
to retest the same area on depth measuring testers are two significant factors that affect
GR&R results. In order to minimize these effects, it is best to do the study on highly
consistent test blocks in order to minimize these built-in variations.
Newage Testing Instruments hardness testers operate are ideally suited for these
studies. Unfortunately, since these studies can only be effectively done on test blocks,
their value does not necessarily translate into actual testing operations. There are a host
of factors that can be introduced when testing under real conditions. Newage testers
excel at testing in real-world conditions by reducing the effects of vibration, operator
influence, part deflection due to dirt, scale, a specimen flexing under load
 Rockwell Hardness Testing
• Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to
indentation, and it is determined by measuring the permanent depth of the indentation. More simply put, when
using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material.

Indentation hardness value is obtained by measuring the depth or the area of the indentation using one of over 12
different test methods. Learn more about hardness testing basics here.

The Rockwell hardness test method, as defined in ASTM E-18, is the most commonly used hardness test method.
You should obtain a copy of this standard, read and understand the standard completely before attempting a
Rockwell test.
The Rockwell test is generally easier to perform, and more accurate than other types of hardness testing methods.
The Rockwell test method is used on all metals, except in condition where the test metal structure or surface
conditions would introduce too much variations; where the indentations would be too large for the application; or
where the sample size or sample shape prohibits its use.
The Rockwell method measures the permanent depth of indentation produced by a force/load on an indenter.
First, a preliminary test force (commonly referred to as preload or minor load) is applied to a sample using a
diamond or ball indenter. This preload breaks through the surface to reduce the effects of surface finish. After
holding the preliminary test force for a specified dwell time, the baseline depth of indentation is measured.

After the preload, an additional load, call the major load, is added to reach the total required test load. This force is
held for a predetermined amount of time (dwell time) to allow for elastic recovery. This major load is then
released, returning to the preliminary load. After holding the preliminary test force for a specified dwell time, the
final depth of indentation is measured. The Rockwell hardness value is derived from the difference in the baseline
and final depth measurements. This distance is converted to a hardness number. The preliminary test force is
removed and the indenter is removed from the test specimen.

Preliminary test loads (preloads) range from 3 kgf (used in the “Superficial” Rockwell scale) to 10 kgf (used in the
“Regular” Rockwell scale). Total test forces range from 15kgf to 150 kgf (superficial and regular) to 500 to 3000 kgf
(macrohardness).
• Test Method Illustration
A = Depth reached by indenter after application of preload (minor load)
B = Position of indenter during Total load, Minor plus Major loads
C = Final position reached by indenter after elastic recovery of sample material
D = Distance measurement taken representing difference between preload and major load position. This distance is used to
calculate the Rockwell Hardness Number.

•
A variety of indenters may be used: conical diamond with a round tip for harder metals to ball indenters ranges with a
diameter ranging from 1/16” to ½” for softer materials.
When selecting a Rockwell scale, a general guide is to select the scale that specifies the largest load and the largest indenter
possible without exceeding defined operation conditions and accounting for conditions that may influence the test result.
These conditions include test specimens that are below the minimum thickness for the depth of indentation; a test
impression that falls too close to the edge of the specimen or another impression; or testing on cylindrical specimens.
Additionally, the test axis should be within 2-degress of perpendicular to ensure precise loading; there should be no
deflection of the test sample or tester during the loading application from conditions such as dirt under the test specimen or
on the elevating screw. It is important to keep the surface finish clean and decarburization from heat treatment should be
removed.
Sheet metal can be too thin and too soft for testing on a particular Rockwell scale without exceeding minimum thickness
requirements and potentially indenting the test anvil. In this case a diamond anvil can be used to provide a consistent
influence of the result.
Another special case in testing cold rolled sheet metal is that work hardening can create a gradient of hardness through the
sample so any test is measuring the average of the hardness over the depth of indentation effect. In this case any Rockwell
test result is going to be subject to doubt, there is often a history of testing using a particular scale on a particular material
that operators are used to and able to functionally interpret.
For more information about Rockwell hardness testing see our guide Selecting a Newage Rockwell Tester or contact us.
 BRINELL HARDNESS TESTING
• Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the
resistance to indentation, and it is determined by measuring the permanent depth of the indentation.

More simply put, when using a fixed force (load) and a given indenter, the smaller the indentation,
the harder the material. Indentation hardness value is obtained by measuring the depth or the area
of the indentation using one of over 12 different test methods. Learrn more about hardness testing
basics here.

The Brinell hardness test method as used to determine Brinell hardness, is defined in ASTM E10.
Most commonly it is used to test materials that have a structure that is too coarse or that have a
surface that is too rough to be tested using another test method, e.g., castings and forgings. Brinell
testing often use a very high test load (3000 kgf) and a 10mm diameter indenter so that the resulting
indentation averages out most surface and sub-surface inconsistencies.

The Brinell method applies a predetermined test load (F) to a carbide ball of fixed diameter (D) which
is held for a predetermined time period and then removed. The resulting impression is
measured with a specially designed Brinell microscope or optical system across at least two
diameters – usually at right angles to each other and these results are averaged (d). Although the
calculation below can be used to generate the Brinell number, most often a chart is then used to
convert the averaged diameter measurement to a Brinell hardness number.

Common test forces range from 500kgf often used for non-ferrous materials to 3000kgf usually used
for steels and cast iron. There are other Brinell scales with load as low as 1kgf and 1mm diameter
indenters but these are infrequently used.
• Test Method Illustration
D = Ball diameter
d = impression diameter
F = load
HB = Brinell result

Typically the greatest source of error in Brinell testing is the measurement of the indentation. Due to
disparities in operators making the measurements, the results will vary even under perfect conditions.
Less than perfect conditions can cause the variation to increase greatly. Frequently the test surface is
prepared with a grinder to remove surface conditions.
The jagged edge makes interpretation of the indentation difficult. Furthermore, when operators know the
specifications limits for rejects, they may often be influenced to see the measurements in a way that
increases the percentage of “good” tests and less re-testing.
Two types of technological remedies for countering Brinell measurement error problems have been
developed over the years. Automatic optical Brinell scopes, such as the B.O.S.S. system, use computers
and image analysis to read the indentations in a consistent manner. This standardization helps eliminate
operator subjectivity so operators are less-prone to automatically view in-tolerance results when the
sample’s result may be out-of-tolerance.
Brinell units, which measure according to ASTM E103, measure the samples using Brinell hardness
parameters together with a Rockwell hardness method. This method provides the most repeatable results
(and greater speed) since the vagaries of optical interpretations are removed through the use of an
automatic mechanical depth measurement.
Using this method, however, results may not be strictly consistent with Brinell results due to the different
test methods – an offset to the results may be required for some materials. It is easy to establish the
correct values in those cases where this may be a problem.
 VICKERS HARDNESS TESTING

Hardness is a characteristic of a material, not a fundamental physical property. It is defined as

the resistance to indentation, and it is determined by measuring the permanent depth of the
indentation.
More simply put, when using a fixed force (load) and a given indenter, the smaller the
indentation, the harder the material. Indentation hardness value is obtained by measuring
the depth or the area of the indentation using one of over 12 different test methods. Learn
more about hardness testing basics here.
The Vickers hardness test method, also referred to as a microhardness test method, is mostly
used for small parts, thin sections, or case depth work.
The Vickers method is based on an optical measurement system. The Microhardness test
procedure, ASTM E-384, specifies a range of light loads using a diamond indenter to make an
indentation which is measured and converted to a hardness value. It is very useful for testing
on a wide type of materials, but test samples must be highly polished to enable measuring
the size of the impressions. A square base pyramid shaped diamond is used for testing in the
Vickers scale. Typically loads are very light, ranging from 10gm to 1kgf, although "Macro"
Vickers loads can range up to 30 kg or more
• The Micro hardness methods are used to test on metals, ceramics,
composites - almost any type of material.
Since the test indentation is very small in a Vickers test, it is useful for a
variety of applications: testing very thin materials like foils or measuring
the surface of a part, small parts or small areas, measuring individual
microstructures, or measuring the depth of case hardening by sectioning
a part and making a series of indentations to describe a profile of the
change in hardness.
Sectioning is usually necessary with a microhardness test in order to
provide a small enough specimen that can fit into the tester.
Additionally, the sample preparation will need to make the specimen’s
surface smooth to permit a regular indentation shape and good
measurement, and to ensure the sample can be held perpendicular to
the indenter.
Often the prepared samples are mounted in a plastic medium to
facilitate the preparation and testing. The indentations should be as
large as possible to maximize the measurement resolution. (Error is
magnified as indentation sizes decrease) The test procedure is subject to
problems of operator influence on the test results.
 CASE DEPTH HARDNESS TESTING

• Case depth is the thickness of the hardened layer on a specimen. Case hardening
improves both the wear resistance and the fatigue strength of parts under dynamic
and/or thermal stresses.
Hardened steel parts are typically used in rotating applications where high wear
resistance and strength is required. The characteristics of case hardening are primarily
determined by surface hardness, the effective hardness depth and the depth profile of
the residual stress. Gears and engine parts are examples where hardening is used.
Effective case depth is the depth up to a further point for which a specified level of
hardness is maintained.
Total case depth is the depth to a point where there is no difference in the chemical or
physical properties.
Case depth testing often involves performing a series of hardness impressions from the
edge of the specimen towards the center. The hardness progression is plotted on a graph
and the distance from the surface to the hardness limit (HL) is calculated.
 CONSIDERATIONS FOR SELECTING A HARDNESS TESTER
• When selecting a hardness tester for your application, it is important for you to consider the following:
Choose the correct test method based on the application.
Plan to use the highest test force and largest indenter possible. Consider the effects of the shape and
dimensions of your test sample.
Answer these key questions:
1. Does your test prescribe a specific hardness scale to be used?
2. What is the material to be tested, and is this material suitable to the type of test method you are
considering?
3. How large is the part, component or specimen to be tested?
4. Is the test point difficult to reach?
5. What is the volume of testing that will be done?
6. How accurate does your test result need to be?
7. What is your budget?
8. What is the required return on investment and do you have ways to measure reductions in costs- yields,
throughput, operator efficiency?
9. What testing problems have you experienced in your current method?
10. How knowledgeable are the users of the tester?

• Verify the test results meet your requirements for accuracy and repeatability.
Consider performing a Gage R&R to gather quantifiable data on how much error is attributed to the operator
and the measurement system employed.
There are significant differences between levels of performance within each classification of tester. A difficult
job on one tester could be very simple and fast on another. So, although hardness testers within a test
method and classification look alike, there are many features that can significantly affect productivity and
accuracy. A good example of features affecting performance is demonstrated in bench Rockwell hardness
testing systems. All can handle moderately long parts using larger anvils or jack rests, however the Versitron
Series can usually test large parts more quickly and accurately, when compared to other bench testers, which
require external support stands or fixtures. The Indentron Series, on the other hand, is much easier to use on
small, awkward parts.
Test Type Test Method Test Force Indenter Type ASTM Measure
Range Reference Method
Rockwell Regular 60, 100, 150 kgf Conical Diamond & E 18 Depth
Small Ball
Rockwell Superficial 15, 30, 45 kgf Conical Diamond & E 18 Depth
Small Ball
Rockwell Light Load 3, 5, 7 kgf Truncated Cone Informal Depth
Diamond
Rockwell Micro 500, 1000 gf Small Truncated Informal Depth
Cone Diamond
Rockwell Macro 500 to 3000 kgf 5, 10mm Ball E103 Depth

Micro hardness Vickers 5 to 1000 gf 136° Pyramid E 384 Area

Diamond
Microhardness Knoop 5 to 1000 gf 130° x 172° E 384 Area
Diamond
Microhardness Rockwell 500 gf to 30 kgf Truncated Cone Informal Depth
Diamond

Brinell Optical 62.5 to 3000 kgf 5, 10mm Ball E 10 Area

Brinell Depth 500 to 3000 kgf 5, 10mm Ball E103 Depth
 SELECTING A ROCKWELL HARDNESS TESTER
Newage Hardness
Key Requirement Features & Benefits
Tester
Model

Testing Indentron Series For demanding applications requiring precise

Accuracy measurement accuracy, the Indentron Series
features a unique lever system that applies the load
in a semi-automatic and virtually frictionless manner.
This eliminates friction-related inconsistencies.
Testing Accuracy in Versitron Series When testing in poor environments containing dirt or
Difficult Environments vibration, the VERSITRON can compensate for
environmental effects and ensure accurate test
results.
High Volume Versitron Series The Versitron has special features ideal for high
Testing volume testing applications. The tester compensates
for the problems commonly experienced in
production environments and high-volume, in-line
applications. Interchangeable test heads keep
operations ongoing. In manual operations test cycles
are fast and testing efficiency is maximized.
Large, Complex Test Parts Versitron Series The Versitron can clamp long parts with up to 240
pounds of force. Bench stands are available with up
to 36" vertical capacity and other configurations can
provide almost unlimited capacity. Using a special
anvil the Versitron is ideal for testing tapered parts.
 SELECTING A BRINELL HARDNESS TESTER
Newage
Key
Hardness Tester Features & Benefits
Requirement
Model
Testing 9000N Series The 9000N Series does not depend on a secondary optical
• The Brinell hardness test method often presents
Accuracy measurement, your test result is reported by the tester automatically.
There is no subjectivity in the measured result.
some challenges for users.
B.O.S.S. The B.O.S.S. optical system minimized operator error and subjectivity.
The software provides a clear image of the indentation and a digital
Poor operating conditions, inexperienced users,
Brinell result. Add B.O.S.S. to any Brinell tester.
tedious7000
high-volume
Series
testing and demanding
The 7000 Series features a hydraulic load system for precision load
applications contribute
control. to reduce accuracy and
repeatability.
High Volume
Production
9000N Series The 9000N Series features automatic depth measurement- tests are
fast and simple. Test results are recorded automatically

B.O.S.S. with 7000 The 7000 Series’ hydraulic stroke and easy-to-use elevating screw
Newage Brinell testers can meet these
Series improves testing throughput. Combined with the B.O.S.S. software,
results are obtained accuracy and quickly.
challenges and help ensure accurate, consistent
results.
Low Volume
Production
NB3010 Series The NB3010 is economical and ideal for low volume applications. Uses
motorized dead weight control and factory air for operation.

Pin Brinell Thousands of users trust the Pin Brinell. It is economical, easy and
reliable.