Metal cutting: Mechanics, surface physics and metallurgy

Abstract

Orthogonal planing experiments have been carried out on 70/30 brass workpieces in the cutting speed range 0·3–150 ft/min. Measurements of chip radius, shear plane angle and the average coefficient of friction between chip and tool have been made and their inter-relationships are successfully explained in terms of a slip line field theory. For a non-hardening workpiece, chip shape is completely determined by the friction stress distribution between chip and tool, but three parameters are required to define this sufficiently, rather than the one, the coefficient of friction, of earlier theories. Lathe turning experiments on a large number of different metals in the speed range 200–800 ft/min indicate that for these materials, chip shape is also determined by the friction stress distribution between chip and tool. The friction stress distribution is determined both by the mechanical strength, under the deformation conditions of the cutting experiment, of the chip material adjacent to the rake face of the tool and by the distribution over the rake face of the ratio of the real to apparent area of contact between chip and tool.