BOR TEKAN KECEPATAN-TINGGI

摘要

A gun drill having a reversed taper approximately ten times greater than the conventional drills, or approximately 0.3 mm per 100 mm, between a tip of the cutting edge and a point some distance away therefrom is provided. The gun drills deep holes at high speed and with sufficient exactness by preventing the peripheral surface of the gun drill from coming into contact with the inner surface of the hole being drilled.