Abstract
HARDNESS is a word which is used in various senses. In dealing with metals, it sometimes means the cutting or scratching hardness, but is more often defined briefly as the resistance to permanent deformation, a property which is of great importance to all users of metals. It is this kind of hardness with which those engaged in minting are chiefly concerned. When a blank is struck in a coining press, the metal is compressed and at the same time forced to flow into the recesses of the dies, and the ease with which this can be done depends on the amount of resistance offered by the metal to a force momentarily applied and tending to deform it. The hardness should therefore be measured by the effects of a sudden blow, and falling-weight machines, such as Shore's scleroscope, offer a ready means of doing this.
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References
Memorandum on The Hardness of Coins, 42nd Annual Report of the Deputy Master of the Mint, 1911, pp. 107”112.
The Annealing of Coinage Alloys, Journal of the Institute of Metals, September, 1912.
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ROSE, T. The Hardness of Coins. . Nature 90, 335–336 (1912). https://doi.org/10.1038/090335b0
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DOI: https://doi.org/10.1038/090335b0