| 摘要 |
PROBLEM TO BE SOLVED: To provide a thread milling cutter with a drill high in breaking strength which can be also used for steel working. SOLUTION: A specified recess is provided in a knife edge side region L1 to an intermediate position of a land from a knife edge 24 of a multiple thread milling cutter 20, but diametrical dimensions of a frank 20b and a bottom 20c are made constant in a heel side region L2 to a heel 26 from the intermediate position on this thread milling cutter with a drill. Consequently, an axial rectangular cross-section becomes larger and stress concentration is relaxed in comparison with the case when a recess is provided to the heel 26 as shown in a dotted line in a drawing 2, and breaking resistant strength is improved without damaging cutting performance of a cutting blade.
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