Patent ID: 8147174
Filing Date: 2012-04-03
Classification: B23B,B27G,Y10T

Abstract:
1. A spade bit comprising: a shaft defining a longitudinal axis of the spade bit; a relatively thin, flat blade attached to the shaft, said blade having a relatively flat first face and a relatively flat second face opposite to said first face, said first face and said second face being joined by a first outer side edge and a second outer side edge; a tip formed along the longitudinal axis; a first cutting edge formed on the blade, said first cutting edge being straight and extending from the tip toward the first outer side edge and a second cutting edge formed on the blade, said second cutting edge being straight and extending from the tip toward the second outer side edge; and a first curved, uninterrupted smooth flute formed in the first face adjacent to and extending along the entire length of the first cutting edge and extending to a first end spaced axially from the first cutting edge and located in the first face and a second curved, uninterrupted smooth flute formed in the second face adjacent to and extending along the entire length of the second cutting edge and extending to a second end spaced axially from the second cutting edge and located in the second face wherein the first flute and the second flute are each formed of a first curved surface and a second curved surface, the first curved surface of the first flute extending from the first cutting edge and the second curved surface of the first flute extending from the first curved surface of the first flute along the longitudinal axis such that the first curved surface of the first flute is disposed between the first cutting edge and the second curved surface of the first flute and the first curved surface of the second flute extending from the second cutting edge and the second curved surface of the second flute extending from the first curved surface of the second flute along the longitudinal axis such that the first curved surface of the second flute is disposed between the second cutting edge and the second curved surface of the second flute, and the first curved surface and the second curved surface having different radii of curvature where the first curved surface is tangential to said second curved surface.