Patent ID: 7018143

Claim:
In a drill bit including an elongate body along which a longitudinal axis extends and in which multiple interlaced spiral flutes are formed about the longitudinal axis, the body including a shaft having a length and terminating between a tapered end and a shank, the tapered end having an apex at which a tip is formed and through which the longitudinal axis passes, the improvement comprising: the shaft provided with relief in the form of a depthwise recess along the length of the shaft between the tapered end and the shank, the recess establishing a transition portion between the tapered end and the shank; first and second inclined cutting edges angularly spaced apart about the longitudinal axis and converging at the tip of the tapered end, the first and second cutting edges angularly inclined from the tip in directions away from the longitudinal axis and terminating at the transition portion to define a wall diameter of a hole cut by the drill bit in a work piece; and first and second leading edge teeth formed by cylindrical and back relief provided at transition portion locations associated with the respective first and second inclined cutting edges, the first and second leading edge cutting teeth clearing from the hole previously cut work piece material debris upon extraction of the drill bit from the hole, irrespective of the direction of rotation of the drill bit, and the transition portion including first and second transition portion cutting edges of different ones of the spiral flutes, the first and second transition portion cutting edges positioned a radial distance from the longitudinal axis to set a diameter for the twist drill.