| 摘要 |
PROBLEM TO BE SOLVED: To prevent a large roundness R on a corner portion of an end face of a columnar projection in the case of extruding the columnar projection in a metal plate. SOLUTION: A conical recess 5 is formed on a short side of the columnar projection 3, the recess 5 is simultaneously formed in the case of extruding the columnar projection 3, and a material at the portion is shifted to the corner portion of the end face of the columnar projection 3. The material at the end face is forcibly shifted to the corner portion simultaneously in the case of forming the columnar projection 3, and the corner is expanded to reduce the roundness.
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