Gun drill with tapered tip

摘要

A gun drill 1 having a reversed taper approximately ten times greater than the conventional ones, or approximately 0.3 mm per 100 mm, between the tip A of the cutting edge 2 and point B some distance away. The drill enables deep holes to be drilled 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.