| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill capable of boring a guide hole and a specified hole, and finishing the holes by the single tool at low cost and favorable workability. SOLUTION: In this drill, a first blade part 9 for boring a guide hole is provided on a conical end surface 6. On an outer circumferential part of a cylindrical part 5, a second blade part 12 for boring a hole comprising a twisted blade is provided to be continuous with the first blade part 9 for boring the guide hole The guide hole 18 and the hole 19 can thus be formed by means of the single tool. Less tools are thus required than conventional to achieve low cost, and boring work can be conducted as continuous work for one time to achieve favorable workability.
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