METHOD AND DEVICE FOR MANUFACTURING HOLLOW RACK BAR

摘要

PROBLEM TO BE SOLVED: To provide a manufacturing method of a hollow rack bar capable of releasing a hollow stock having a rack formed thereon from an upper die of a die without complicating a die structure. SOLUTION: A steel pipe (a hollow stock) 1A having a working wall part with a rack being formed thereon by a tooth die 14c on a part close to one end is held by a die 13 having an upper die 14 and a lower die 15 having a downward tooth die 14c while a part on the other end side of the steel pipe being protruded to the side of the die 13. Next, a material of the working wall part is subjected to the plastic flow from the inner side to the outer side of the steel pipe 1A by the core 25 to be press-fitted in the steel pipe 1A to form the rack according to the tooth die 14c. Thereafter, the steel pipe 1A with the rack formed thereon is released from the upper die 14 while the die 13 is opened, and the steel pipe 1A is taken out of the die 13. The release is performed by using a releasing member 42 which is provided on an outer part of the die 13 and abutted on a projecting part 1Ab of the steel pipe 1A projected from the die 13 from the upper side. COPYRIGHT: (C)2009,JPO&INPIT