| 摘要 |
PROBLEM TO BE SOLVED: To provide a one-tip type throwaway tip with similar two tips which can further reduce the load on a screw in drilling, and a drill holder forming a throwaway drill combined therewith. SOLUTION: In the tip 1, a through hole 1a through which the screw 3 fitting the tip 1 to the holder 2 is formed close to a forward side in the drilling direction of a base portion 1d thicker in wall than an inner blade side protruded portion 13 with an inner blade 11 formed thereon and an outer blade side protruded portion 14 with an outer blade 12 formed thereon. In the holder, the through hole through which the screw is passed and a drill hole with the screw screwed therein are formed closer to a forward portion in the drilling direction of a pair of holding pieces holding the tip.
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