Patent ID: 9623488
Date: 2017-04-18
CPC Classifications: B23B,Y10T

Claim:
1. A drill, comprising: a substantially cylindrical cutting portion comprising wherein the second rake surface does not have a surface closer to the rotation axis than the second central surface, wherein a rear end of the first central surface is located closer to the rear end of the cutting portion than a rear end of the first outward surface, and wherein a rear end of the second outward surface is located closer to the rear end of the cutting portion than a rear end of the second central surface, wherein, for each of the plurality of first rake surfaces, in a direction parallel to a corresponding one of the plurality of first cutting edges and in a portion most adjacent to the corresponding first cutting edge, a width of the first central surface is smaller than a width of the first outward surface, and wherein, for each of the plurality of second rake surfaces, in a direction parallel to a corresponding one of the plurality of second cutting edges and in a portion most adjacent to the corresponding second cutting edge, a width of the second central surface is larger than a width of the second outward surface.