1.Adopts mechanical and manual testing method,without electrical device. 2.High precision,easily read the scale value from dial Usage Range:Hardened and surface hardened steel, hardening and tempering steel, tempered steel, cold and hard casting parts, forging parts, hard alloy steel, aluminum alloy, bearing steel, carburized steel sheet, etc. Technical SpecificationsRockwell Scales HRA, HRB, HRC ...