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Show TH 5 wit PRINCIPLE five or six variables O SCIENTIFI MANAGEMEN but that it was manifestl impossibl to solve a problem containing twelve variables in any other way tha by the slow process of "trial and error. A quick solution was, however, so much of a necessity in ou every-day work of running machine-shops, that in spite of the smal encouragement received from the mathematicians, we continued a irregula periods throug a term of fifteen years to giv a larg amount of time searching for a simple solution Four or five me at various periods gave practically their whole time to this work, an finally, while we were at the Bethlehem Steel Company, the sliderule was developed which is illustrated on Folder No. 11 of the pape "On the Art of Cutting Metals," and is described in detail in th paper presented by Mr. Carl G. Barth to The American Society o Mechanical Engineers, entitled ""Slide-rules for the Machine-shop as a part of the Taylor System of Management" (Vol. 25 of th Transactions of the American Society of Mechanical Engineers) By mean of this slide-rule, one of these intricate problem solved in less than a half minute by any good mechanic ca b whethe he understands anything about mathematics or not, thus makin available for every-day, practical use the years of experimentin on the art of cutting metals This is a good illustration of the fact that some way can alway be found of making practical, every-day use of complicated scientifi data, which appears to be beyond the experience and the range o the technical training of ordinary practical men These slide-rule have been for years in constant daily use by machinists having n knowledge of mathematics A glance at the intricate mathematical formule (see page 57 which represent the laws of cutting metals should clearly show th reason why it is impossible for any machinist, without the aid o these laws, and who depends upon his personal experience, correctl to guess at the answer to the two questions What speed shall T use What feed shall T use even though he may repeat the same piece of work many times To return to the case of the machinist who had been working for ten to twelve years in machining the same pieces over and over again there was but a remote chance in any of the various kinds of wor which this man did that he should hit upon the one best method o doing each piece of work out of the hundreds of possible method which lay before him In considering this typical case it must als be remembered that the metal-cutting machines throughout ou |