Patent ID: 7364390

Claim:
A twist drill for cutting metal, said twist drill comprising a maximum diameter of at most ten millimeters and an integral body, said twist drill comprising: a first drill bit portion comprising at least two cutting edges; a second drill bit portion comprising at least two cutting edges; a middle portion disposed between said first drill bit portion and said second drill bit portion; each of said first drill bit portion and said second drill bit portion and said middle portion together form said integral body; at least two helical chip flutes being disposed to run from said at least two cutting edges of said first drill bit portion to said at least two cutting edges of said second drill bit portion; said chip flutes each comprising a first portion disposed in said first drill bit portion, a second portion disposed in said second drill bit portion, and a third portion disposed in said middle portion; said first portion of each of said chip flutes comprising an asymmetrical cross-sectional profile about a radius of said twist drill intersecting at approximately the middle of a corresponding one of said chip flutes; said second portion of each of said chip flutes comprising an asymmetrical cross-sectional profile about a radius of said twist drill intersecting at approximately the middle of a corresponding one of said chip flutes; and said third portion of each of said chip flutes comprising a symmetrical cross-sectional profile about a radius of said twist drill intersecting at approximately the middle of a corresponding one of said chip flutes.