Definitions for "Rockwell Hardness"
Keywords:  indent, softer, diamond, hard, steel
Units of hardness measure by the resistance of a material (typically metal) to indentation by a spherical tipped conical diamond indentor (Rockwell C and A) or, in the case of softer materials, a hardened steel sphere indentor (Rockwell B).
A relative measure of hardness. Rockwell C Scale is used for hard materials, Rockwell B for softer materials, such as sheet metal.
A method of measure hardness - normally for bearings between 55 to 58 on the 'C' scale.