Importance

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Abstract

The invention comprises a drag-type drill bit including a bit body adapted for rotative movement in a pre-determined direction in use and having an operating end face, and a plurality of cutting members mounted in the bit body. Each of the cutting members has a stud portion disposed in a respective recess in the bit body and defining the inner end of the cutting member, and a cutting face generally adjacent its outer end facing outwardly through the operating end face of the bit body and terminating in an outermost cutting edge. The centerline of the stud portion is rearwardly inclined, from the outer end to the inner end, with respect to the direction of movement in use, taken at the midpoint of the cutting edge, at a first angle from 80.degree. to 30.degree. inclusive. The cutting face is oriented such that the tangent to the cutting face at the midpoint of the cutting edge and in the central plane of the cutting member is disposed at a second angle, from 18.degree. to 75.degree. inclusive, with respect to the centerline of the stud portion.

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First Claim