Perrygraf Machining Calculator Slide Rule for LeBlond

This yellow and white rectangular paper rule has a white paper slide and is held together with four metal rivets. On the front, the top scales allow one to calculate the revolutions per minute for a given work diameter and surface speed. The bottom scales allow calculation of the time in minutes and seconds for a given feed rate, length of cut, and R.P.M. The back of the instrument has tables for converting from fractions to decimals and for finding the suggested carbide surface speed of a lathe for different materials.

Perrygraf Corporation, described in 1979.3074.03, made this instrument in 1949 for the R. K. LeBlond Machine Tool Company of Cincinnati. A salesman could attach his card to the back of the calculator and give it to a client. Richard K. LeBlond (1864–1953) began making machines in 1887 and became known for the quality of his lathes in the 1890s. Products included lathes for manufacturing bicycles and automobile crankshafts. The company employed 1,200 workers and made a mammoth lathe for boring artillery during World War II. In 1981 Makino Corporation of Japan purchased the company. The factory in Cincinnati is now Rookwood Pavilion shopping center.

Perrygraf slide rules in the collection include: 1983.3009.04, 1983.3009.05, 1983.3009.06, 1987.0108.03, 1988.0323.01, 1988.0325.01, and 1992.3103.01.

References: Tom Wyman, "Slide Chart Calculators – A Modest Proposal," Journal of the Oughtred Society 13, no. 1 (2004): 6–10; Kenneth L. Cope, American Lathe Builders: 1810–1910 (Mendham, N.J.: Astragal Press, 2001), 89; Tony Griffiths, "LeBlond - USA," Machine Tool Reference Archive, http://www.lathes.co.uk/leblond/.

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