JPS569021A - Screw working method of thin-walled pipe - Google Patents

Abstract

PURPOSE: To work the screws having sufficient practicable strength on a thin-walled pipe easily and highly accurately by fitting a mandrel die into the thin-walled pipe and revolving these under pressure between plural circular dies.

CONSTITUTION: With circular dies 10, 11 and a mandrel die 12 being held spaced, a thin-walled pipe P being the work is fitted onto the die 12. The outside diameter of the die 12 is made approximately the same as the inside diameter of the pipe P. In this state, the dies 11W12 are rotated and the movable die 11 is moved to the die 12 side to push the die 12 and press it to the stationary die 10. As a result, the pipe P revolves in the same direction as that of the die 12 by receiving the rotating force of the die 12 from the inner side and the rotating forces of the dies 10, 11 from the outer side. The peripheral wall portions of the pipe P press-contacted with the dies 10W12 are pressed by the die screw parts 10a, 11a from the outer side and the screw parts 12a being reverse in crest and through from those of said parts from the inner side, thus it plastically deforms along the screw shape, whereby screws S₁, S₂ are formed on the inside and outside surfaces.

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