Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts (1880)
D. Appleton and Company, Benjamin, Park, 1849-1922 · New York, D. Appleton · leaf 764
notbe used in holes too small for the size of the tap,and thus is prevented a great deal of tap break-age. The bottom of the thread of the first par-allel step (from A to B) is below the diameter of A, so as to relieve the sides of the thread of friction and cause the tap to enter easily, inefirst… … VYvViWraftVA-KAVV--
Mechanical engineering -- Dictionaries
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