| 摘要 |
A metal bolt or cap screw fastener has a head, a shank of reduced cross section and a threaded portion, which fastener is configured to be manufactured using cold forming automatic bolt making machines of concurrent configuration. The reduced cross section shank provides additional elastic stretch and reduces stress throughout the fastener upon application of external joint parting loads, as compared to conventional fasteners with nominal diameter shanks. The inventive fastener has at least three straight longitudinal ribs along the length of the reduced cross section shank. The longitudinal ribs extend laterally outward from the surface of the shank a distance substantially corresponding to the fastener nominal diameter so as to center the fastener within round holes. During cold forming, the fastener shank diameter is made to the same or somewhat larger diameter than the not yet threaded part of the bolt.
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