Instruments which evaluate the hardness of materials can be divided into three categories: indentation (Rockwell, Brinell), scratch, and rebound. Rockwell testers with an HRC scale provide fast (≤10s) readings for heat treated steels with test forces ranging from 60-150 kgf. For castings and forgings, Brinell testers (500-3000 kgf) with ball indenters determine HB values. These machine models comply with the ISO 6507, ASTM E18 and surface preparation (roughness Ra ≤ 1.6μm) checklists for metallic machining quality control documents.