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178 above. He trusts that his object may be realized and that the publication of this book may be followed by similar works on other trades and more particularly on the details of machine shop practice, in which he is especially interested.

As a machine shop has been chosen to illustrate the application of such details of scientific management as time study, the planning department, functional foremanship, instruction cards, etc., the description would be far from complete without at least a brief reference to the methods employed in solving the time problem for machine tools,

The study of this subject involved the solution of four important problems:

First. The power required to cut different kinds of metals with tools of various shapes when using different depths of cut and coarseness of feed, and also the power required to feed the tool under varying conditions.

Second. An investigation of the laws governing the cutting of metals with tools, chiefly with object of determining the effect upon the best cutting speed of each of the following variables:

(a) The quality of tool steel and treatment of tools (i.e., in heating, forging, and tempering them).

(b) The shape of tool (i.e., the curve or line of the cutting edge, the lip angle, and clearance angle)

(c) The duration of cut or the length of time tool is required to laat before being re-ground.

(d) The quality or hardness of the metal being cut (as to its effect on cutting speed).

(e) The depth of the cut.