Comb cracks - Comb cracks on the tool occur during thermal alternating stress. They usually result from applications in interrupted cutting. The tool heats up very strongly during the engagement and is cooled down strongly by the cooling lubricant after leaving the workpiece.

Transverse cracks - So-called transverse cracks also occur mainly in interrupted cutting (e.g. milling). These are the result of mechanical alternating stress (brief succession of cutting force changes).