| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill bit wherein rotary drilling of a drill hole drilling face is performed by cooperating respective parts of a plurality of cutting blades, and of a durable life is prolonged by reducing eccentric wear of the cutting blades. SOLUTION: In this drill bit, a plurality of cutting blade parts 3a, 3b, 3c are formed to a cutting blade chip 3, and a joint edge of a cutting face 6 and a flank 7 formed to each of the cutting blade parts 3a, 3b, 3c is used as a cutting blade 4. An inner end of each cutting blade 4 is abutted at a cutting tip apex 8. Notch recessed parts 5a, 5b, 5c are formed to each cutting blade 4. COPYRIGHT: (C)2004,JPO
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