| 摘要 |
PURPOSE:To obtain a tooth form excellent in surface roughness and strength by preforming a tooth form lower in height and wider in width than final tooth form and then obtaining required final tooth form by finishing work and thereby reducing amount of cutting. CONSTITUTION:A tooth form part 13 is formed flat in specified position of a rack material 11 made of a solid round bar, and a tooth form 12 is preformed in the tooth form part 13. The tooth form 12 has a profile lower in height and wider in width than the final tooth form 16. The volume of the tooth form 12 is made substantially equal to that of the final tooth form 16 to obtain required final tooth form by succeeding finishing work, for instance press work. Then, the tooth form 12 of the rack material 11 is finished to the final tooth form 16 by a die provided with a die which is corresponding exactly to the final tooth form 16. |
