BUILT-UP EDGE ELIMINATION IN MIRROR CUTTING OF HARDENED STEEL

A built-up edge will normally give a poor finish. The conventional way of eliminating the built-up edge is to increase cutting speed and feed (i.e., increase tool face temperature). It is shown here that a built-up edge can also be eliminated if the workpiece hardness is above a critical value. This critical value is such that the workpiece hardness be somewhat greater than half the hardness of the built-up edge that forms at low hardness and speed, since the built-up edge hardness is between 2 and 3 times the corresponding workpiece hardness. It is suggested the reason for this is that the hardness of the workpiece must be less than the hardness of the built-up edge, otherwise the built-up edge disappears. This new method of eliminating the built-up edge by use of hard work material prevents built-up edge formation even at low feeds and speeds, thus making it possible to produce extremely a good (mirror) finish under these conditions.