Rockwell hardness (RH),
Definition of Rockwell hardness (RH):
Standard method for measuring hardness (resistance to penetration) of materials, expressed as a number assigned to the depth of penetration of a diamond cone or steel ball. There are several scales of Rockwell hardness of which the A (for extremely hard materials), B (for medium hardness materials), and C (for the material reading over 100 on the B-scale) are the most common. Hardened tool steel, for example, typically reads 62 on the C scale, and is identified as 62Rc.
Meaning of Rockwell hardness (RH) & Rockwell hardness (RH) Definition