| 摘要 |
PURPOSE:To form a row of teeth making the metal of flat part cut into rugged part of a forming die and to mass-produce light rack bars at high yield by forming a segmental cylindrical pipe having flat one side by press working a side of a pipe, fitting it into a forming die and pressing a punch into the pipe. CONSTITUTION:Lower opposing faces 11a, 12a of a pair of semi-cylindrical sectional dies 11, 12 for primary forming are in close contact without gap, and upper opposing faces 11b, 12b recede to the side and concave circular arcuate faces 11c, 12c are formed between sectional dies 11, 12. A material pipe 21 of nearly the same diameter with the rack bar is fitted tightly in the concave circular arcuate faces 11c, 12c. When a square rod-shaped press die 14 is pressed into a parallel groove 13, a segmental cylindrical primary formed body 22 having a flat part 22b is formed. Sectional dies 31, 32 for secondary forming are semi- cylindrical, and rugged faces 31a, 32a corresponding to the row of teeth of the rack bar are formed on the upper face of a recessed hole. A punch 33 is segmental cylinder having diameter nearly equal to inner diameter of the primary formed body 22. The primary formed body 22 is fitted in sectional dies 31, 32 for forming, and the punch 33 is pressed in forcibly to form a rack bar. |
