| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for working a square pipe with both tapers by which working man-hour is reduced as compared with compression molding and bulging work, the quality is uniformly stabilized, the strength is raised, and appearance is improved by having no welded part. SOLUTION: The pipe is gradually worked from a tip by inserting the combination of a mandrel 12 on which a projecting part 13 is formed and a straight mandrel 15 into the interior space of the square pipe stock 2 and, after that, the front taper part and rear taper part are swaged by similarly gradually working the pipe from the opposite side. COPYRIGHT: (C)2004,JPO
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