| 摘要 |
PROBLEM TO BE SOLVED: To provide round dies for form rolling, which reduces the number of retoolings in form-rolling a screw. SOLUTION: A pair of round dies 20 and 30 for form rolling are respectively column-shaped and peripheral surfaces thereof are respectively separated by grooves 21-24, 31-34, to form a plurality of processing surfaces 25a-25d, 35a-35d. The processing surfaces 25a-25d are respectively provided with respective stripe-shaped projections 26a-26d for form-rolling different screws. As same as the processing surfaces 25a-25d, the processing surfaces 35a-35d are respectively provided with respective stripe-shaped projections 36a-36d for form-rolling different screws. Therefore, the desired thread can be formed on a workpiece by holding the workpiece between the dies 20 and 30 while rotating the dies 20 and 30 at a predetermined angle. Even in the case of changing the kind of the screw to be form-rolled, the screw can be form-rolled without replacing the dies 20 and 30. COPYRIGHT: (C)2008,JPO&INPIT
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