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Rockwell hardness test
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<p>The Rockwell hardness test is a <a href="/facts/Hardness/PtGn6E20">hardness</a> test based on <a href="/facts/Indentation_hardness/sbYCdPar">indentation hardness</a> of a material. The Rockwell test measures the depth of penetration of an indenter under a large load (major load) compared to the penetration made by a preload (minor load). There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale. Larger numbers correspond to harder materials. </p><p>When testing metals, indentation hardness correlates linearly with <a href="/facts/Tensile_strength/Cv2jPplR">tensile strength</a>. </p>