To provide a rack for steering apparatus and manufacturing method therefor with which the rack is light weight and the degree of filling of a blank to a tooth form is improved and the forming precision of the rack tooth is improved.
In a die 31 at the lower side in an intermediate forming process, since the width W1 of the interval at the upper opening end of an inclining restricted surface 311 is largely formed a little rather than the outer diameter size D of the outer periphery 11 of a first rack blank 1, the upper half part of the rack blank 1 has no binding force at the forming time. Therefore, the tooth width W2 at the tooth base part of the rack teeth 13 and 14 which finished the intermediate forming process, is formed so as to project to the outside in the radial direction from the outer periphery 11 of the first rack blank 1. Since a second process of the intermediate forming process is performed only the processing which makes the rack teeth thin and the tooth height high, the forming load can be low. Further, in the first process and the second process of the intermediate process, since the tooth width of the tooth base part in the rack teeth 13, 14 is not restricted, the die is not made to closed state, and since the forming load can be low, the service life of the die is extended.
OTSUKA SEIJI
HIROTA KOTARO
Kazuo Sadashige