| 摘要 |
PURPOSE:To improve a padding and to mass-produce the screw heads excellent in the accuracy of shapes by forging a preparatory formed part material whose head is upset forged by a forming punch with projected stripe to form plural axial grooves, further by pressing with a central auxiliary punch. CONSTITUTION:The member whose head (b) is preparatively formed by a die 10 and a punch 11 is forged by the head forming punch 20 with the projected stripe to form plural axial grooves 3. Furthermore, the press is performed by the auxiliary punch 24 passing through the center of the forming punch 20. The padding on the formed surface 21 is improved to mass-produce the screw heads excellent in the accuracy of shapes.
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