| 摘要 |
In producing a semicircular washer having a projection to prevent rotation formed thereon, a blank material in the form of a flat bar is forced to pass a roll caliber between upper and lower forming rolls arranged in a pair and bent on and along one of the forming rolls while being pressed in the breadthwise direction to become a semicircular washer. The semicircular washer then has its outer marginal portion punched out by means of a punch and a die to form thereon a projection for preventing rotation. The method ensures an increase in the yield of semicircular washers having a projection for preventing rotation and enables the projection to be formed in any position on the washer as desired.
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