Abstract
The purpose of the paper is to investigate the significance of periodic removal of metal particles deposited during cutting in the pores of the grinding wheel. A measuring technique is described, and experimental results are given, which indicate that wheel life, topography, chatter vibration, workpiece skin hardness, and metallographic structure can be improved considerably by applying a special process of debris removal from the working periphery of the grinding wheel.
In other experiments using lubricants it is found that simple mechanical removal of debris may also be advantageous. A new technique of intermittent application of a lubricant is described. This is shown also to be effective when grinding a heated workpiece.
A new technique for examining the ground surface is described. This utilizes ¾-in inserts, which are heat-treated and then ground with the main body of the selected workpiece material. These inserts are subsequently removed and examined by metallographic sectioning. Microhardness traverses across the surface and in depth show marked variations due to the rapid heating of the surface during grinding and the immediate very rapid quenching. A 0·45 % C steel of general hardness 700 K.d.n. was, for example, increased to 1100 near the surface. At greater depths, the diffusion of heat tempers the quenched material, and the hardness falls again with further increase in depth. This excessive skin hardening can be avoided by ultrasonic treatment of the wheel at regular intervals during grinding.
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