| 摘要 |
PROBLEM TO BE SOLVED: To extremely reduce the number of high strength bolts by enlarging a frictional force between steel materials. SOLUTION: A washer body 1C having a bolt insertion hole 1B at the center of a disc 1A is formed with satin-like recessed and projecting parts 1D on both contact pressure surfaces 1A1, 1A2. Each the recessed and projecting part 1D comprises plural projecting parts and recessed parts formed side-by-side. The washer body 1C is manufactured by forging or casting and is hardened by using a special steel or by quenching.
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