The measure of the material hardness as demonstrated by one of the following tests: Brinnell Hardness: Material hardness determined as a measurement of the depth of residual penetration of a test piece upon the surface of the material after a specified load is applied. The Brinnell Hardness (HB) is determined with a ball pressure test using a steel ball having a diameter of 0. 413 inch (10. 5 mm) or 0. - Knoops Hardness: Material hardness readings taken with a microhardness tester using a load of 1. - Microhardness:The hardness measured in a very small area with a specified type of indenter that has a small specified load, relative to the standard hardness tests described above. - Rockwell Hardness: Material hardness determined as a measurement of the depth of residual penetration of a test piece upon the surface of the material after a specified load is applied. A Rockwell B Hardness test (HRB) uses a steel ball having a 0. 0625 inch diameter (1. 59 mm) with an initial test force of 22 lbs (98 N) and a test force of 198. - Vickers Hardness: Material hardness determined as a measurement of the depth of residual penetration of a test piece upon the surface of the material after a specified load is applied. The Vickers Hardness (HV) test uses a diamond pyramid having a four-sided surface and an apex angle of 136 , conducted in accordance with DIN 50 133.