| 摘要 |
A hand operated countersink has a shaft attached at one end to a cutting insert and at the other end to a handle, wherein said cutting insert is substantially of isosceles triangular shape. The insert has at least two cutting edges each disposed along an equal side of the triangle, one of the cutting edges being operative to cut when the shaft is rotated in one direction, and the other cutting edge being operative to cut when the shaft is rotated in the other direction. In a preferred embodiment, the insert has four cutting edges, two disposed along opposite edges of one equal side of the triangle, and two disposed along opposite edges of the other equal side of the triangle.
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