METHOD AND DEVICE FOR HARDENING RACK BAR

摘要

PROBLEM TO BE SOLVED: To prevent the variance of tooth pitch caused by hardening distortion, and to prevent the generation of bend caused by the hardening distortion when a rack bar used in a steering device of an automobile is hardened. SOLUTION: In the hardening operation of a rack bar 1 to implement the hardening by heating at least the whole length of a rack part, and injecting a cooling solution thereon, the cooling solution is injected on the rack part from at least one slit having at least the length of the rack part. At least two projecting parts 19 are provided on a jacket 25 parallel thereto on both sides of a cooling solution injection slit 20, and the jacket is one of restrictive jigs to prevent the rack bar 1 from being bent.