Rockwell number
noun Metallurgy.
a numerical expression of the hardness of a metal as determined by a test (Rockwell test) made by indenting a test piece with a Brale, or with a steel ball of specific diameter, under two successive loads and measuring the resulting permanent indentation.
Origin of Rockwell number
1930–35,
Americanism; named after Stanley P.
Rockwell, 20th-century American metallurgist