| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill capable of maintaining high rigidity of a drill body while also allowing the obtaining of satisfactory hole positional accuracy. SOLUTION: The drill of the present invention has only one cutting discharge groove 11 formed in the outer periphery of a bit 10. A leading edge protruding farthest towards the tip in the axial direction in a tip flank 12 is composed at a single point and located on an axis O. When bit is viewed from the tip side in the direction of axis, tip flank is in the form of a multilevel surface composed of second through fourth flanks 14B, 14C and 14D arranged along the peripheral direction, and a reverse side first flank 14E surrounded by second through fourth flanks and intersecting with axis O. COPYRIGHT: (C)2007,JPO&INPIT
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