Method of producing a vibration resistant fastener

A method of producing a vibration resistant fastener having a shank with at least a portion of its length provided with an external helical thread configuration including a root, a crest and a flank therebetween having a plurality of skewed ramp and buttress configuration serrations thereon, comprising the steps of:

• providing die members having ribs for forming the external
• thread on round stock material, each said die member including a segment having serrations provided on one side of each said rib within said segment for imparting a complementary irregular serration configuration on the load bearing flank surface of the fastener being produced, each of said serrations being in the form of teeth extending inwardly from the crest producing portion of said ribs to termination inwardly of the pitch diameter at a point spaced from the root producing portion of said ribs, each of said teeth comprising an inclined ramp portion extending from a root to a crest thereof with a buttress extending between said crest and the root of an adjacent serration in a plane generally parallel with the longitudinal axis of the fastener being produced, the height of said buttress between said crest and the root of an adjacent serration being greater at said crest producing portion of said ribs than at said point spaced from said root producing portion of said ribs, and each said buttress being oriented at a skewed angle with respect to the crests of said ribs;
• rolling the round stock material between said die members to form the external helical screw threads on a portion thereof and to impart the complementary irregular serration configuration on a segment of the load bearing flank of the fastener being rolled therebetween;
• and
• smoothly disengaging each said skewed angle buttress on the die members adjacent the crest producing portion of the ribs from the complementary skewed angle buttress formed on the stock as it continues rotating, without tearing material therefrom.