Abstract Hot or cold forging is used to manufacture self-countersinking threaded fastener heads, such as self-countersinking screw heads and the like, which, during manufacture, can be removed from the heading die by straight axial movement. One aspect of the present invention involves the use of a relatively narrow included angle for the tapered underside of the head in combination with an axially extending sharp edge collar cutter originating at the periphery of the head. Another aspect of the present invention involves providing elongated cutters and cutter reliefs along the tapered underside of the head. The cutter reliefs form cutter recesses with the cutting edges at the top thereof. The recesses are shaped so that respective imaginary lines extending axially downwardly from any point on the surface of the recess encounter no other portion of the fastener. Moreover, in this aspect of the invention the cutting edges slope in the opposite direction of the slope of the screw threads on the fastener.
A self-countersinking threaded fastener comprising: a threaded elongated body portion with screw threads sloping in a first direction; a head portion including a tapered underside having an included angle between 45* and 55*, and four uniformly spaced cutter edges sloping in the direction opposite said first direction, and a recess below each of said cutter edges having a shape such that respective imaginary lines extending axially downwardly from every point on said recess encounter no other portion of said fastener, and driving means comprising a recess in the top of said head portion having four radially extending portions extending into said head portion to respective ones of those regions of the tapered underside of the head which are positioned between said cutting edges.
Claim 2
Dependent Claim
123 words
A self-countersinking threaded fastener comprising: a threaded elongated body portion with screw threads sloping in a first direction; a head portion including a tapered underside having an included angle between 45* and 55*, and four uniformly spaced cutter edges sloping in the direction opposite said first direction, and a recess below each of said cutter edges having a shape such that respective imaginary lines extending axially downwardly from every point on said recess encounter no other portion of said fastener, and driving means comprising a recess in the top of said head portion having four radially extending portions extending into said head portion to respective ones of those regions of the tapered underside of the head which are positioned between said cutting edges.
Claim 3
Dependent Claim
14 words
A fastener as defined in claim 1 wherein said included angle is approximately 50*.