Rockwell Hardness Test

A hardness testing technique in which an indenter is pressed into a test sample by a weight or load. The indenter contacts the surface of the test sample upon the application of a light pre-load, called the minor load. This “sets” the indenter in the sample and determines the starting point of indenter penetration. A heavier major load is then applied. This pushes the indenter into the test sample. The indenter is then withdrawn and the distance to which it has penetrated is measured and used to calculate a Rockwell hardness number. The shape of the indenter and the amount of weight applied as the major load varies depending on the material which is being tested. The indenter may be a cone-shaped diamond or a 1/16″ diameter metal ball, and the major load may range from 15 to 150 kilograms. These variations are identified by a letter designation, for example, Rockwell A, B, C, etc. or a number/letter combination such as 15N, 15T, or 30N.