| 摘要 |
A method of providing an undercut "bowtie" slot in the head of a fastener such as a screw or bolt, and the resulting interim and final fastener products. The method consists of only two heading steps, starting with either a preform or a simple blank. In the first heading step a forming blow is applied which produces a "bowtie" shaped slot having side walls that are not undercut and a single, continuous ellipsoidal bulge projecting upwardly from the head adjacent to and substantially coextensive with each edge of the slot. In the second heading step a forming blow is applied which compresses the material of the ellipsoidal bulges down into the head to form a radiused undercut slot configuration that is continuous and substantially coextensive with the length of the slot. |
