https://www.nist.gov/publications/standard-grade-rockwell-diamond-indenters-key-worldwide-unified-rockwell-hardness-0
Since the 1980's, the European Community (EC) has established a unified Rockwell C hardness (HRC) scale by averaging several national scales, which come from ea
standard graderockwelldiamondindenterskey
https://www.nist.gov/publications/tolerancing-form-deviations-rockwell-diamond-indenters
The spherical tip of Rockwell diamond indenters tends to be manufactured either a flat- or sharp-shaped surface because of the anisotropy property of the diamon
tolerancingformdeviationsrockwelldiamond