HP9 steel has a Rockwell hardness rating of 35.7 HRC. This rating corresponds to 335 HB on the Brinell hardness scale and 352 HV on the Vickers scale.
Hardness tests are used to determine the hardness of metals and alloys. Hardness is measured by applying a known load to the surface of a material with an object that makes an indentation. The size of the indentation made is used to calculate hardness. Different metals and alloys have specific ranges of hardness. White cast iron, for example, has a high Brinell hardness rating of 415, while soft brass has a value of 60.