| 摘要 |
A throw-away rotating tool includes at least two grooved portions 13b, 13c formed on each of erected portions 13 and at least two protrusions 26, 27 for fitting into and removal from respective grooved portions 13b, 13c and projected from a projecting coupling portion 23, and the grooved portions 13b, 13c are formed asymmetrically about an axis O and the protrusions 26, 27 are formed asymmetrically about the axis. Thus, the direction in which the projecting coupling portion 23 can be coupled to the erected portions 13 is uniquely determined. Consequently, variations in lip height and run-out can be minimized. As a result, occurrence of a bend and an increase in machined hole diameter during drilling can be prevented, thereby making it possible to minimize variations in machining accuracy and tool life.
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