Chip formation and chip breaking processes in metal cutting

This investigation has been carried out to analyse and discuss the chip formation and chip breaking processes in metal cutting and to demonstrate the degree of agreement between the theoretical and experimental results. Particular attention has been given to the chip breaking control. Different materials such as steels (low, medium and high carbon steels), aluminium alloy and copper were tested under different cutting conditions using different tool geometries with ground and clamped chipbreakers, and cutting was carried out dry and with coolant. The chips obtained were measured, and the experimental results were plotted. For the chips to be controlled at the cutting zone and effectively transported from the vicinity of the machine tool, it is essential chipbreakers are used. Chip breaking effectiveness was found to be influenced chiefly by the ratio of chip curl radius to feed. The condition for minimum cutting force was found to be influenced chiefly by the chipbreaker proportion ratio, i.e. the width/height for ground step chipbreaker and width/angle of the inclination of the chipbreaker wedge for clamped wedge chipbreaker. Chipbreaker proportions are limited on the one hand by the need to get sufficiently broken chips and on the other hand by the need to avoid extensive increase in cutting forces, which should not increase by more than about 10%. During this work it was established that the use of chipbreaker having optimum dimensions will not only give broken chips with reduced cutting force, but also that there will be no increase in tool wear due to the presence of a chipbreaker. Coolant was found to be helpful in promoting good chip breaking performance. Charts were drawn for quickly finding chipbreaker dimensions for effective chip breaking over a wide ranee of cutting conditions and materials. A theoretical expression for chip breaking effectiveness in terms of chip curl radius and chipbreaker proportions was suggested.