| 摘要 |
A drill has a shank with a central axis of rotation and at least one insert on one end of the shank. The insert has at least two cutting edges. The first cutting edge has a negative radial rake and the second cutting edge has negative axial and positive radial rake surface. The first and second cutting edges cooperate to form a radiused hole when rotated about the central axis. Also, the cutting insert is composed of hard wear resistant material. The insert has top and bottom faces and a peripheral wall joining the top and bottom faces. The insert body is polygonal when viewed in plan. One of the top and bottom faces acts as a seating face and the other acts as a cutting face. There are first cutting edges formed on opposite sides of the cutting face at the juncture of the cutting face with the peripheral wall. One end of each of the first cutting edges terminates in a juncture with a second cutting edge that extends from the cutting face toward the seating face. The first and second cutting edges cooperate to form a radiused hole when rotated about a central axis.
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