An investigation into the effect of metal transfer between a single-point cutting tool and the work surface on surface finish in turning



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Mathematical relationships defining surface finish as a function of tool geometry and feed have been derived. Above high cutting speeds (750 feet per minute) these mathematical relationships describe the surface finish obtained in actual cutting situations with adequate precision. But at low speeds, there exists a large discrepancy between the theoretical and actual values (the ratio between the two values is often as high as 20:1). The objective of this thesis is to measure, under practical cutting conditions, the actual surface finish for a series of feeds, throughout the practical cutting range of a steel of specified characteristics. The surface finish is measured with a profilometer, and relevant data, such as cutting forces, chip parameters, and depth of cut are also recorded. The following conclusions are drawn from the experimental data: 1. There exists three speed regions for a given feed in which the surface finish improves, worsens, and again improves. In the higher speed ranges, the actual surface finish approaches the theoretical values for the surface finish. 2. The primary reason for the fact that surface finishes change with respect to speed when tool geometry and feed are held constant is found in the phenomena of built-up edges and their variations of size with respect to speed. 3. A finer feed at low speeds does not necessarily improve the surface finish.