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Rockwell number

noun, Metallurgy
1.
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
1930-1935
1930-35, Americanism; named after Stanley P. Rockwell, 20th-century American metallurgist
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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