Rockwell scale Rockwell scale The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. 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 (see below). When testing metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of
Leeb rebound hardness test resulting in a greater value 1000×"v/v". A magnetic impact body permits the velocity to be deduced from the voltage induced by the body as it moves through the measuring coil. The quotient 1000×v/v is quoted in the Leeb rebound hardness unit HL. While in the traditional static tests the test force is applied uniformly with increasing magnitude, dynamic testing methods apply an instantaneous load. A test takes a mere 2 seconds and, using the standard probe D, leaves an indentation of just ~0.5 mm in diameter on steel or steel casting with a Leeb hardness of 600 HLD. By comparison,