| 摘要 |
PROBLEM TO BE SOLVED: To provide a bolt and nut type fastening tool which is not difficult to be loosened and removed after the nut is once tightened by a predetermined torque. SOLUTION: This fastening tool is provided with a bolt and a nut capable of being threadly engaged with a male screw portion of the bolt. The nut 5 is provided with an inner nut 7 of a truncated cone shape, an outer nut 6 turnably engaged with an outer side of the inner nut 7 and having an outer periphery of a hexagonal shape, and a connection pin 8 inserted in the inner nut 7 and the outer nut 6 so as to cross a space therebetween and capable of being broken and separated when a predetermined or more tightening torque is applied to the outer nut 6. A projecting end portion of the inner nut 7 is projected and provided at a bearing surface side of the nut 5.
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