This cutting speed calculator from Proctor and Co is a Lawrence 10-G slide rule made in Peru, Indiana, USA.1. It is included in this collection because it represents a different approach to cutting speed calculations as implemented in the two Nomographs in the collection.
1 The history of Lawrence Engineering Service (and its successor, Engineering Instruments) is described in Bruce Babcock, Journal of the Oughtred Society, vol 5 no 2 pp 55–61, Oct 1996. A further article by David Rance is in the IM2011 Proceedings, 2011. Thanks also to David McFarland, “Re:Proctor&CoCuttingSpeedCalculator”, Private Communication, 15 July 2012 (↑)
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