MANUFACTURE OF RACK BAR FOR RACK AND PINION TYPE STEERING DEVICE

PURPOSE:To improve a dimension accuracy of a rack bar projecting part by executing a forming of a bulging part by a coining die having a forming surface which has bulged more large, in accordance with a degree in which a bulging part of a rack bar stock bulges from a prescribed shape. CONSTITUTION:With regard to a manufacture of a rack bar 1 having a rack tooth 2 and a projecting part 4 which is displaced smoothly, along an axis 3, a stock 15 having a rack tooth 6 and a bulging part 8 resembling 3 prescribed shape, along an axis 7 is prepared, and a gauge 15 having a gauge surface 14 of a prescribed shape on the back 13 is made to contact by pressing, by which a degree bulging from a prescribed shape is measured. Subsequently, in accordance with a degree in which the shape of the bulging part 8 bulges from a prescribed shape, the stock 5 is brought to coining and finished to the rack bar 1 between a lower die 12 having a forming surface 11 which has bulged larger than a prescribed shape, and an upper die 10 having a forming surface 9 of the tooth 6. In this way, a rack bar having substantially a projecting part of its prescribed dimension and shape is obtained.