| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill which minimizes a degradation in hole positioning precision at the time of biting in a slope during execution of drilling. SOLUTION: According to the structure of the drill, a point angleθis set in the range of 170 to 180°, and therefore a radial component of force applied thereto at the time of biting in a workpiece is reduced. Preferably a cutting edge 1 of the drill is preferably formed by combining a straight line and a concavely curved line R with each other. COPYRIGHT: (C)2004,JPO
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