| 摘要 |
PROBLEM TO BE SOLVED: To provide a bolt having a hexagonal-curve contour portion formed at the outside and its manufacturing method. SOLUTION: The invention relates to a bolt having hexagonal-curve contour portion at the outside and its manufacturing method. A bolt head formed generally in accordance with one type torque standards comprises the outside hexagonal-curve contour portion 5 for positively operating force and a flange 4 having an inclined face 41 extending to the outside hexagonal-curve contour portion 5 at an angleα. According to the invention, the inclined face 41 of the flange 4 is connected directly to the outside hexagonal-curve contour portion 5, therefore producing a great decrease in total height k of the head 3, and a height t1 of the outside hexagonal-curve contour portion 5 assures positive operation of force. In the method according to the invention, the flange 4 and the outside hexagonal-curve contour portion 5 are shaped by scraping using a scraper or upsetting and forming press. In the case of the latter, a recess is provided at a portion of the head.
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