Patent ID: 7530772
Filing Date: 2009-05-12
Classification: B23B,Y10T

Abstract:
1. A twist drill for drilling blind holes with planar bottom surfaces, said twist drill comprising: a shank portion and a fluted portion comprising two chip flutes; a planar end face being disposed at an end of said fluted portion opposite said shank portion; said planar end face comprising two main cutting edges and a chisel edge disposed there between; said two main cutting edges being substantially aligned with one another and joined by said chisel edge to form a continuous cutting edge; each of said main cutting edges and said chisel edge being disposed to lie in a plane perpendicular to the central longitudinal axis of the drill; and each of said main cutting edges being disposed to trail, in a direction of rotation of said drill, a distance behind a center line disposed coplanar to said main cutting edges which said center line extends through the center longitudinal axis of said drill and substantially parallel to each of said main cutting edges, the distance between said center line and said main cutting edges being substantially less than the length of either of said main cutting edges.