| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method for a hollow shaft having a projection such as a cam shaft which has excellent dynamic balance at high- speed rotation. SOLUTION: In bulging a hollow stock pipe by accommodating the hollow stock pipe 4 with hollow bodies 5a and 5b for a projection to be plastically worked fitted thereon in a vertically openable/closable bulging die 1 comprising fixed dies 2a and 3a and a movable die split in dies 2b, 3b and 2c, 3c, and dies 2d, 3d and 2e, 3e, this manufacturing method comprises (1) a step of accommodating the hollow stock pipe after the fixed dies and each movable die are set with a predetermined spacing therebetween, (2) a step of bulging the accommodated hollow stock pipe and bringing an inner surface of the hollow body into contact with an outer surface of the hollow stock pipe, and (3) a step of continuing the bulging while pressing and moving the movable dies 2d, 3d and 2e, 3e by die moving fixtures 8a and 8b, and fitting the hollow body via the hollow stock pipe to a hole die inside the bulging die in which the fixed dies and each movable die are abutted on each other.
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