Indentation test that applies a minor load, then a major load, and converts the permanent difference in depth into a hardness number. Hardened steel is read on the C scale (HRC) with a 150 kgf load and diamond cone; soft steel and nonferrous metals on the B scale (HRB) with a 1/16-inch ball. Superficial scales such as 15N and 30N use light loads for thin cases and sheet. Readings on round parts need a cylinder correction.
Rockwell hardness is reading 54, 55, 53 on the shaft, add the round correction and it's in.
Grind through scale and decarb before testing, or the first reading tells you about the skin, not the part.
Also heard as
- Rockwell
- HRC
- HRB
- Rockwell C
- superficial Rockwell
Related terms
Points
Shop shorthand for Rockwell numbers, as in a part running two points high on hardness.
Microhardness
Hardness measured with very small loads under a microscope, used for thin cases and individual phases.
File hard
Hard enough that a sharp file skates across the surface without biting, roughly 58 HRC and up.
Case depth
Thickness of a hardened surface layer, measured from the surface to a specified hardness or structure.