| 摘要 |
PROBLEM TO BE SOLVED: To provide a convenient method for manufacturing a hollow rack bar with great accuracy. SOLUTION: In a method for manufacturing a hollow rack bar, a mandrel 51 is drawn in the axial direction relative to a hollow pipe-like work W. Then, the portion-to-be-worked of the work is pressed against the rack which is moved by the pressing part formed on the mandrel 51 to form a rack tooth profile on the work W. The method includes a thinning process wherein radial sections are reduced at both ends outer than the circumferential center of the portion-to- be-worked. Namely, the difference in thickness between the region near the circumferential center and the region near the both ends of the portion-to-be- worked on which the rack teeth is formed, is reduced in advance before the rack teeth are formed. Consequently, the difference in rigidity between them is reduced to prevent spring back developing locally.
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