Patent ID: 7789599

Claim:
A drill comprising: a body that is rotated about an axis; a cutting edge that is formed at a tip end of the body; and a thinning edge that is formed continuously with the cutting edge and that is formed close to the axis of the body, by having a thinning at the tip end of the body, wherein the thinning edge is formed such that a rake angle of the thinning edge relative to the axis of the body changes depending on a location of the thinning edge, and wherein the thinning edge includes a first thinning edge that is located close to the axis of the body and a second thinning edge that is located closer to the cutting edge relative to the first thinning edge where the first and second thinning edges are formed in a substantially linear manner seen from the direction of the tip end of the body, and the rake angle of the second thinning edge is a positive angle larger than that of the first thinning edge.