This standard specifies the Rockwell hardness test for steel which has the following principle of test.
The test consists in forcing an indenter (cone or ball) into the surface of a test piece in two operations and measuring the permanent increase (e) of the depth of indentation under the test conditions specified below. The unit of measurement for e is 0.002 mm ; from the measurement of e, a number known as the Rockwell hardness is deduced .
1 unit = 0.002 mm