Patent ID: 6443674
Filing Date: 2002-09-03
Classification: B23B,Y10T

Abstract:
A self-centering drill comprising:(a) shank, a body, and a cutting end, all formed integrally in the drill: (b) said body interposed between said shank said cutting end, said body having a pair of helical flutes and a corresponding pair of helical lands; (c) said cutting end including a substantially flat bottom section having primary cutting lips which are relief ground and are formed convex relative to said bottom, said primary cutting lips forming a primary point angle, measured by forming an angle that extends from the primary cutting lips and passes through the rotational axis in the body, and a helical crown having a helical crown point tip that extends from said bottom section, said helical crown point tip having self-centering cutting lips; (d) wherein the outside edges of said bottom section are chamfered to form secondary cutting lips which are radially relieved, said secondary cutting lips forming a secondary point angle, measure by forming an angle that extends from the secondary cutting lips and passes through the rotational axis in the body, (e) said primary point angle being greater than said secondary point angle.