| 摘要 |
PURPOSE:To position a boring bar in a rotary cylinder accurately as well as to improve the accuracy of finishing, by installing a pressing piece in a lower end of the boring bar, and also installing a positioning mechanism inclusive of thin piece. CONSTITUTION:Plural cutting tools 63 are clamped to a boring bar 7, and a bearing hole 11 of a work W is bored. A pressing piece 185 is installed in a lower end of the boring bar 7, inserting this lower end into a support hole 79, and the pressing piece 185 is fitted in a groove 184. The lower end of the bar 7 is made contact close to an inner surface of the support hole 79 by work of a positioning mechanism 182 inclusive of the pressing piece 185. Therefore, even if an inner diameter of the support hole 79 is set to be somewhat large for reasons of insertion and vice versa, a shaft center at the lower end of the bar 7 always comes to the same position to the support hole 79, so that accuracy of finishing is improved.
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