| 摘要 |
PURPOSE:To obtain a rack shaft sufficient in strength by inserting a flat part into the inner hole of a hollow bar stock by forming it on the side face of an auxiliary hollow stock, subjecting the hollow stock to plastic deformation with the press of a pressing die and locking the hollow bar stock and auxiliary hollow stock by plastically deforming the flat part of the auxiliary hollow stock. CONSTITUTION:An auxiliary hollow stock 2 is inserted into the inner hole 4 of a cylindrical hollow bar stock 1 and located at the inner hole of the rack tooth profile forming position of the hollow bar stock 1. The press die attached to an upper die and engraved with a tooth profile is then advanced and the hollow bar stock 1 and auxiliary hollow stock 2 are subjected to plastic deformation to press-form a rack tooth. In the case of pressforming the rack tooth by forming a flat part on the auxiliary hollow stock 2, then, the power to advance the push die is reduced because of the hollow bar stock 1 only being subjected to plastic deformation at the beginning. The rack shaft is obtd. by retreating the push die and pulling a core die 6 out of the auxiliary hollow stock 2. The rack shaft is subjected to cutting, if necessary, and to induction hardening by leading a refrigerant to the inner part.
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