The Rockwell hardness test is based on an inverse relationship to the measurement of the additional depth to which an indenter is forced by a heavy total or major load beyond the depth resulting from a previously applied preliminary or minor load. Rockwell hardness values are expressed as a combination of a hardness number and a scale symbol representing the indenter and the minor and major loads. The hardness number is expressed by the symbol HR and the scale designation.
- Cast irons
- Thin materials
- Cemented carbides
- Deep case hardened materials
- Shallow case hardened materials