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This cutting speed calculator from Proctor and Co is a Lawrence 10-G slide rule made in Peru, Indiana, USA.[^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^].  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.

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