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Rockwell hardness testing

The Rockwell hardness test is a fast method, making it ideal for quick hardness testing. We give a definition of the Rockwell hardness test, as well as practical information of how to apply it in practice.

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The Rockwell hardness test at a glance:

  • Generally used for larger samples
  • No optical readout
  • Can be used for advanced tests
  • Standards: ASTM E18, ISO 6508 and JIS Z 2245
Find your next Rockwell Hardness Tester

Definition of the Rockwell hardness test

The Rockwell hardness test is often used as a ‘quick test’ on the production floor or in the laboratory, mainly for metallic materials. However, it can also be used for more advanced tests, such as the Jominy test (End Quench Test). Due to the relatively high loads used, application of the Rockwell hardness test is generally limited to larger sample geometries.

The Rockwell test calculation

The Rockwell hardness test calculation (HR) is made by measuring the depth of an indentation made with a diamond or tungsten carbide ball.

HR = E - e
E: is a constant of 100 (diamond) or 130 (ball) units
e: is the penetration depth in units of 0.002 mm

Indenters
The Rockwell hardness test utilizes 1 of 5 different indenters:

  • Diamond cone
  • Tungsten ball in sizes 1/16", 1/8", 1/4", or 1/2"

Main loads
The Rockwell hardness test utilizes 1 of 6 different main loads:

  • 15 kgf, 30 kgf, 45 kgf, 60 kgf, 100 kgf, or 150 kgf


In total, this gives 30 different Rockwell scales. Each one is characterized by a different combination of indenter type and main load, and is suitable for a particular material or application (for example, HRA, HRB, HRC, HR30N).

Definition of the Rockwell hardness test method

The Rockwell hardness test methods are described by a number of scales, characterized by a standard, an indenter type, and a load.

Examples of Rockwell hardness test methods:

  • HRE 1/8” diameter tungsten carbide ball indenter, 100 kgf major load
  • HR30N (Superficial Rockwell 30N-scale): Diamond cone indenter, 30 kgf major load
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Application of the Rockwell hardness test

Surface preparation

Before application of the Rockwell hardness test, you must prepare the surface of the material to be tested. The required surface condition for the Rockwell hardness test depends on the load used.

The Rockwell hardness test is used for macro hardness tests, which are generally defined as tests that use indentation loads below or equal to 1 kgf. Therefore, a ground surface is usually sufficient, and sometimes no preparation is required.

Loads

STANDARD LOAD RANGE

ISO 6508

15 kgf - 150 kgf

(147.1 - 1471 N)

ASTM E18

15 kgf - 150 kgf

(147.1 - 1471 N)
  • Indentation time: 2-6 seconds
  • Sample thickness ASTM: At least 10 times the indentation depth for both indenters
  • Sample thickness ISO: Diamond indenter: At least 10 times the indentation depth. Tungsten carbide indenter: At least 15 times the indentation depth.

Download our Application note about Hardness Testing

Jominy testing

The Jominy test (End Quench Test) is a standardized test procedure used to determine the hardenability of steel, and it can be performed using any Vickers micro hardness tester.

  • The procedure is described in the following standards: ASTM A255 / ISO 642 / DIN 50191 / BS 4437

The Jominy test involves heating a cylindrical steel test piece to an austenitizing temperature (~980°–1010°C) and quenching (cooling) from one end, with a controlled and standardized jet of water. After quenching, the hardness is measured at intervals taken from the quenched end. The test method used is either HRC or HV30.

The hardness variation along the test surface is a result of microstructural variation that arises as the cooling rate decreases with the distance from the quenched end. The harder the material at a given distance from the end, the higher the hardenability of the steel.

Both the Vickers and the Rockwell hardness tests are often used for Jominy testing. When selecting which to use, pay attention to the relevant standards, as well as the usual criteria when choosing between different types of hardness test.

Find out more about the Vickers hardness test

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Jominy testing

Overview of typical applications for Rockwell hardness scales

Test Method Load Indenter Type Application
Standard test method
A 60 kgf Diamond cone Cemented carbides, thin steel and shallow case-hardened steel
B 100 kgf 1/16"" WC Ball Copper alloys, soft steel, aluminium alloys, malleable iron etc.
C 150 kgf Diamond cone Steel, hard cast irons, pearlitic malleable iron, titanium, deep cased hardened steel
D 100 kgf Diamond cone Thin steel and medium case-hardened steel and pearlitic malleable iron
E 100 kgf 1/8"" WC Ball Cast iron, aluminium and magnesium alloys, bearing metal
F 60 kgf 1/16"" WC Ball Annealed copper alloys, thin soft sheet metals
G 150 kgf 1/16"" WC Ball Phosphor bronze, beryllium copper, malleable irons
H 60 kgf 1/8"" WC Aluminium, zinc, lead
K 150 kgf 1/8"" WC Ball Bearing metals and other very soft or thin materials including plastics
L 60 kgf 1/4"" WC Ball Bearing metals and other very soft or thin materials including plastics
M 100 kgf 1/4"" WC Ball Bearing metals and other very soft or thin materials including plastics
P 150 kgf 1/4"" WC Ball Bearing metals and other very soft or thin materials including plastics
R 60 kgf 1/2"" WC Ball Bearing metals and other very soft or thin materials including plastics
S 100 kgf 1/2"" WC Ball Bearing metals and other very soft or thin materials including plastics
V 150 kgf 1/2"" WC Ball Bearing metals and other very soft or thin materials including plastics
Superficial test method
N 15 kgf
30 kgf
45 kgf		 Diamond cone Rockwell superficial scales use lower loads than a regular Rockwell test and are used to test materials too thin or small for the regular scales or outside the regular ranges. Generally, diamond indenters are used for hard materials while Ball indenters are used on soft materials
T 15 kgf
30 kgf
45 kgf		 1/16"" WC Ball Rockwell superficial scales use lower loads than a regular Rockwell test and are used to test materials too thin or small for the regular scales or outside the regular ranges. Generally, diamond indenters are used for hard materials while Ball indenters are used on soft materials
W 15 kgf
30 kgf
45 kgf		 1/8"" WC Ball Rockwell superficial scales use lower loads than a regular Rockwell test and are used to test materials too thin or small for the regular scales or outside the regular ranges. Generally, diamond indenters are used for hard materials while Ball indenters are used on soft materials
X 15 kgf
30 kgf
45 kgf		 1/4"" WC Ball Rockwell superficial scales use lower loads than a regular Rockwell test and are used to test materials too thin or small for the regular scales or outside the regular ranges. Generally, diamond indenters are used for hard materials while Ball indenters are used on soft materials
Y 15 kgf
30 kgf
45 kgf		 1/2"" WC Ball Rockwell superficial scales use lower loads than a regular Rockwell test and are used to test materials too thin or small for the regular scales or outside the regular ranges. Generally, diamond indenters are used for hard materials while Ball indenters are used on soft materials

ISO 6508 and ASTM E18 = A B C D E F G H K N T
ASTM E18 = L M P R S V W X Y

Download our brochure covering our Rockwell hardness testers

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Downloads and webinars

Whether you're just starting with hardness testing or are an experienced professional, this curated selection of resources is here to assist you in your work.

Take advantage of downloadable reference posters for easy use in your lab, and dive into expert-led webinars hosted by our application specialists to deepen your understanding of hardness testing techniques and methods.