| 摘要 |
PROBLEM TO BE SOLVED: To optimize the construction of a drill head totally made of a hard material for an impact drill with long life, considering the low frictional properties of the drill head while it is in a brand new condition. SOLUTION: This drill head 1 made totally of a hard material for an impact drilling tool has a main cutter 3 with a main cutting edge 4 and a subcutter 5 with a subcutting edge 6, arranged in a position deviated circumferentially to the main cutter 3. In addition, the subcutting edge 6 includes at least, a partially arc-like part 7 which extends obliquely in the radial direction, while becoming apart from a rotary shaft A inside in the radial direction. Besides, the subcutting edge 6 includes a straight linear outside part 8 which extends obliquely in the radial direction outside in the radial direction of the arc-like part 7. COPYRIGHT: (C)2008,JPO&INPIT
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