Sources and scope for this page: ASTM E140-12b, covering the definition of hb / hrc / hv hardness scales. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
Brinell presses a 10 mm ball and measures the indentation diameter — good for soft to medium materials and for castings with coarse structure. Rockwell C presses a diamond cone and reads depth directly — the shop standard for hardened steel. Vickers presses a diamond pyramid and is used for thin sections and case-hardened surfaces.
Converting between them is approximate and defined by ASTM E140. Above about 60 HRC the conversion spreads out, and for unfamiliar alloys it should not be relied on.
Common misuse
Converting HRC to HB for a hardened steel as though the relationship were exact. It is a table of approximations and the scatter grows at high hardness.