Methods of machine shop work : for apprentices and students in technical and trade schools (1914)
Halsey, Frederick A. (Frederick Arthur), 1856-1935 · New York : McGraw-Hill · leaf 88
n.^ It was the recognitionof the inevitable error due to the taking of sizes from graduatedscales that led Bodmer, about 1840, to design plug and ringgages. Sizes can be taken from such gages with calipers with afar higher degree of precision than from graduated scales. A set of Whitworth plugs and… … Fig. 50.—Whitworth plug and ring gages. are still good fits, showing absence of wear, the gages are not ofan accuracy which would now be considered sufficient for suchinstruments. For many years such gages supplied the only means ofintroducing standard measurements of their degree of accuracy.They…
Machine-shop practice
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