| 摘要 |
PURPOSE:To prevent the generation of burrs and improve work efficiency by equalizing the sum of volume of concavities of the upper and lower dies with the volume of plastic worked parts of a blank material. CONSTITUTION:The width of the concavity 21 of an upper die 20 is made greatter than the diameter D of a material 9, and the sectional form of the concavity 22 of a lower die 23 is made nearly semicircular, and the radius of curvature is made greater than the diameter D. The sum of volume of the two concavities is made substantially equal to the volume of plastic worked part of the material 9. Accordingly, when the material 9 is pressed between the upper die 20 and lower die 22, rack teeth are cut on its upper surface. At the same time, the lower surface is plastic worked along the concavity 23 and the diameter is increased slightly. Thus, the generation of burrs can be prevented. |
