Public domain
Conversion. Copper and brass processing. This sample of brass strip is being tested on a Rockwell Hardness Testing Machine. This test is based upon the depth a steel ball penetrates the metal. A minor load is applied first to hold the ball in position, and then a major load is applied. The dial on t
From the collection of Library of Congress. Free to download, adapt and use — no permission needed.
Credit lineConversion. Copper and brass processing. This sample of brass strip is being tested on a Rockwell Hardness Testing Machine. This test is based upon the depth a steel ball penetrates the metal. A minor. 1942-01-01. Palmer, Alfred T., United States. Office For Emergency Management. Farm Security Administration/Office of War Information Collection, Library of Congress. Public domain.
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