| 摘要 |
PURPOSE:To thread two screws having pitches different from each other and to prevent loosening of a screw part, by a method wherein a continuously vari able speed change gear is inserted in the threading system of a conventional lathe, or an electric motor-drive continuously variable speed change gear is disposed on the upper feed rest of a conventional lathe. CONSTITUTION:When a continuously variable speed change gear 6 is inserted in the threading system of a conventional lathe, a reference pitch p3 higher than a pitch p1 of a screw part 2 is selected, change gears 5 and 7 and an idle gear 12, capable of threading at the p3, are geared with each other. The speed ratio of the continuously variable speed change gear 6 is regulated to p2/p3 to perform threading at the p2. After the speed ratio of the continuously variable speed change gear 6 is re-regulated to p1/p3, after a threading bite 8 is matched with the screw groove of a subordinate complete male screw part 3, a reference complete male screw part is threaded at the pitch p1. This constitution enables threading of two screws a different pitch which enables provision of an effect to prevent loosening of a screw part.
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