Micro crack formation in hardmetal milling tools

Hardmetal milling tools are frequently used for machining of hard materials, e.g. titanium alloys. Such tools are often reground after the end of their lifetime. This is intended to increase the resource and the economical efficiency of the required but expensive hardmetal blanks. However, end users often notice a decreased lifetime when using reground tools. Subsurface damages that are not removed during regrinding probably cause this effect. This paper investigates the formation of cracks in hardmetal milling tools and consequently suggests grinding strategies that consider the removal of all present micro cracks. The results show a correlation between the required amount of material removal and the size of the optically measurable breakouts at the cutting edge.