| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent looseness of a nut while inexpensively mass-producing a bolt-nut. SOLUTION: This bolt-nut has a looseness preventive mechanism, and has a bolt 1, a washer 2 for inserting this bolt 1, and a nut 3 screwed in the bolt 1. The bolt 1 has a key groove 4. The washer 2 is arranged by projecting a projecting part 5 guided by the key groove 4 of the bolt 1 on the inner periphery, and is fitted around the bolt 1 so as not to rotate by inserting this projecting part 5 into the key groove 4. A surface of opposing the washer 2 to the nut 3 is a saw-toothed recess-projection surface 6 rotatable in the direction for fastening the nut 3, and nonrotatable in the inverse direction, and a surface of opposing the nut 3 to the washer 2 is a recess-projection surface 6 having the same pitch as the saw-toothed recess-projection surface 6.
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