Hard twist-drill for glass reinforced plastics, esp epoxy - has very thin titanium monoxide coating generating little heat

摘要

A hard metal twist-drill for drilling GRP plates, esp. copper-faced, glass fibre-reinforced epoxy plates, has the cutting edges and the following grooved portion of the drill faced with a hard coating of titanium monoxide. The maximum thickness of this coating is pref. 1 mu, and the coating may be coloured. Prevents excess heating of the material being drilled. The cutting surfaces do not easily crack.