City Research Online

Abstract

Previously published work on the mechanics of chip breaking, the performance of chip forming devices and cutting with controlled contact length cutting tools is critically appraised and the need for a greater understanding of the chip control process is established.

Machining with tools having chip forming grooves on the tool face is often characterised by the existence of a special built-up-edge at values of undeformed chip thickness greater than a particular value. The variation in the configuration of this special built-up-edge with different land configurations is examined, it is thought for the first time.

The stability of the special built-up-edge with change in cutting speed is investigated by examination of the machined surface, and the effect on surface roughness and subsurface deformation of cutting with negative lands is determined, The results indicate that for given cutting conditions at values of primary rake angle less than a particular value, sidespread of the workpiece is pronounced, This results in excessive cutting force, surface roughness and subsurface damage. However, it is shown that at more positive primary rake angles than the critical value, the surface profile produced during oblique machining may be smoothed.

A model of the chip formation when using controlled contact length tools is proposed involving a pattern of tangential velocity discontinuities. Using this model, reasonably good correlation is obtained between the theoretical and the experimental relationship between shear angle and undeformed chip thickness at low cutting speeds.

Modification of the model to account for observed changes in the configuration of the special built-up-edge at high temperatures, enables the effect on cutting performance to be predicted.

A mechanism of chip formation when using chip forming grooves at high cutting speeds is proposed, For this case, a procedure for determining a relationship, not previously established, between the tool configuration and chip curl radius is outlined. Also a method of determining the tool configuration for chip breaking in a specified feed range is proposed.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General) T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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