| 摘要 |
PROBLEM TO BE SOLVED: To provide a form rolling die capable of forming a thread which has a base parallel to the axial direction of a screw and a sectional shape symmetric to the perpendicular bisector of the base while the lead angle is variable. SOLUTION: The round-die type form rolling die comprises a thread form rolling ridge part to form a thread on a screw blank by being turned while it is pressed against the screw blank, and the axis of rotation forming a center of rotation of the thread form rolling ridge part. The thread form rolling ridge part is formed in a sectional shape in the direction of the axis of rotation of the thread form rolling ridge part, which has a base parallel to the axis of rotation, and is symmetric to the perpendicular bisector of the base. The thread form rolling ridge part has a wavy swell having one period of the length of each integer partition of the circumference with the screw effective diameter of a desired male screw formed on the screw blank by the form rolling die as the reference. COPYRIGHT: (C)2006,JPO&NCIPI
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