Cutting tool damage in interrupted cutting

The shaping and turning of a workpiece with key ways, milling and the high speed turning of small workpieces, in which the risk of tool chipping and breakage decreases in the order given, exhibit three danger areas: tool entry, tool exit and cyclic heating and cooling. The relative importance of these depends on the dimensions of the cut, the cutting speed, the heating time/cooling time, the workpiece and tool materials, the shape of the tool and the geometry of the entry and exit. A better understanding of the phenomena occurring during tool entry is required, and therefore the cutting forces during entry and exit have been studied. The chipping caused by the exit phenomena has been explained using the results of a finite element study of the workpiece and the tool. The effect of rounding or chamfering the edges of carbide cutting tools for interrupted cutting, e.g. milling, is discussed and the work required before this can be optimized is outlined.