| 摘要 |
PROBLEM TO BE SOLVED: To reduce the manhour and decrease the length of raw material to improve yield of the material by increasing the board thickness of at least a portion of a lug piece corresponding to the female screw part by punching or platic working suh as compressing working or the like. SOLUTION: The sectional portions of root parts 21, 22a, 22b of tubs 4 forming fork branch parts are pressed as indicated by a broken line to be plastic deformed so as to improve surface roughness. Secondly, in at least one side lug piece of a pair of lug pieces 7, that is, in a portion corresponding to a screw hole to be bored in the post processing, a small-diameter punch is driven from one side to form a projection 9 on the opposite side. Subsequently, bending is performed to form a hub tubular part 11, and the paired lug pieces 7, 7 are made opposite to each other substantially parallel to the radial/ direction from the hub tubular part 11. A bolt insert hole and a seat is formed on one of the lug pieces 7, 7, and a screw hole screw-engaged with the bolt screw part is bored in the other thereof to complete a fork.
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