| 摘要 |
PROBLEM TO BE SOLVED: To prevent a bolt from being removed by providing a nut further fitted to a bolt where a fastening nut is previously fitted in such a manner that when the displacement on the shaft center line of the nut is taken to be X, and an outside diameter in an arbitrary X is taken to be Y, dY/dX is always positive or negative. SOLUTION: When a displacement on the shaft center line of a nut 1 is taken to be X and an outside diameter in an arbitrary X is taken to be Y, dY/dX is always positive or negative. The nut 1 has an inclined outer peripheral surface 2, so that a wrench can not be firmly held. The outer peripheral surface 2 of the nut 1 is let have high hardness by carbonizing to easily slip. Thus, even if a special wrench such as a pipe wrench or the like is used, the nut is not loosened. The bearing surface 3 is also carbonized to easily slip. When the wrench is held on a stop nut N and the nut 1 is rotated with the stop nut N to loosen the nut, the rotation of the stop nut N is not transmitted to the nut 1. The nut 1 is firmly fixed to a bolt B by a fixing agent applied to the screw part 4.
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