| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a hollow rack shaft with which load is reduced and whose forming accuracy is improved. SOLUTION: After forming a flat part, a steel tube 10 is loaded in a forming die having the tooth profile of a rack, plural mandrels 16 which are different in the size of a pushing-out part are successively inserted into the steel tube 10 and, when the rack teeth 1a are formed by gradually pushing out the flat part by the pushing-out part from the inside of the flat part to the side of the tooth profile of the rack, first, a mandrel 16 having a straight-line-shaped pushing-out part is inserted, next, a mandrel 16 having a concave part 26 where the approximately middle of the pushing-out part is recessed along the axial direction and the rack teeth 1a are formed. A mandrel 16 having smaller width than the inside diameter of the steel tube 10 is inserted and the rack teeth 1a are formed. |
