| 摘要 |
PROBLEM TO BE SOLVED: To improve the biting between a bolt and a nut at their initial threaded engagement. SOLUTION: Either a first taper-like chamfered part (7) having a chamfering angle equal to the flank angle of an internal thread part is formed at the end part of an opening on the bolt-inserting side of a nut or a second taper-like chamfered part having an angle larger than the flank angle is formed outside the first chamfered part (7). Moreover, a bolt-side chamfered part 22 having an angle equal to the angle of the first chamfered part 7 on the nut side is formed at the tip part of the bolt. By seating the bolt-side chamfered part 22 on the first chamfered part 7 of the nut, the attitude of the bolt-and-nut can be adjusted so that the axes of the bolt and the nut further coincide with each other, Since the chamfering angles of both first chamfered part 7 of the nut and the chamfered part 22 of the bolt are nearly equal to the flank angle of the internal thread, the length of an incomplete thread part can be shortened, and consequently defective engagement of the bolt-and-nut becomes hard to occur.
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