Method of making self tapping thread forming screw

Claim 1

A method of making a self-tapping thread-forming headed screw comprising the steps of: (a) forming a blank having a longitudinal axis, including a generally right-cylinder shank portion and a tapered frusto-conical shaft portion at the work entering end of the shank portion; (b) forming three spaced flat portions on the blank extending longitudinally on the blank parallel with the longitudinal axis, terminating at opposite ends within the shank portion and the shaft portion; (c) forming a delta formed region at the head end of each of the flat portions, the delta formed region including a peripherally arcuate convex surface tapering gradually to the flat portion and having side edges such that the side edges and the edge of the delta formed region closest to the screw head, which bound the delta formed region, define an isosceles triangle; and (d) thread rolling the blank to form male threads on the shank portion and the frusto-conical shaft portion except at the work entering end thereof, whereby a second length of spoon-like recesses are formed on the crest portions of the threads passing on each delta formed region, adjacent ones of the spoon-like recesses having a same width and decreasing depth in the direction from the work entering end to head end of the screw.

Claim 2

A method of making a self-tapping thread-forming headed screw comprising the steps of: (a) forming a blank having a longitudinal axis, including a generally right-cylinder shank portion and a tapered frusto-conical shaft portion at the work entering end of the shank portion; (b) forming three spaced flat portions on the blank extending longitudinally on the blank parallel with the longitudinal axis, terminating at opposite ends within the shank portion and the shaft portion; (c) forming a delta formed region at the head end of each of the flat portions, the delta formed region including a peripherally arcuate convex surface tapering gradually to the flat portion and having side edges such that the side edges and the edge of the delta formed region closest to the screw head, which bound the delta formed region, define an isosceles triangle; and (d) thread rolling the blank to form male threads on the shank portion and the frusto-conical shaft portion except at the work entering end thereof, whereby a second length of spoon-like recesses are formed on the crest portions of the threads passing on each delta formed region, adjacent ones of the spoon-like recesses having a same width and decreasing depth in the direction from the work entering end to head end of the screw.

Claim 7

A method of making a self-tapping thread-forming headed screw comprising the steps of: (a) forming a blank having a longitudinal axis, including a generally right cylinder shank portion and a tapered frusto-conical shaft portion at the work entering end of the shank portion; (b) forming three spaced flat portions on the blank extending longitudinally on the blank parallel with the longitudinal axis, terminating at opposite ends within the shank portion and the shaft portion; (c) forming a delta formed region at the head end of each of the flat portions, the delta formed region including a peripherally arcuate convex surface tapering gradually along its length to the flat portion; (d) thread rolling the blank to form male threads of width substantially less than the length of each of the delta formed regions on the shank portion and the frusto-conical shaft portion except a first length of the frusto-conical shaft portion at the work entering end thereof, whereby a second length of spoon-like recesses are formed on the crest portions of the threads passing on each delta formed region, adjacent ones of the spoon-like recesses having a same width and decreasing depth in the direction from the work entering end to head end of the screw.

Claim 8

A method of making a self-tapping thread-forming headed screw comprising the steps of: (a) forming a blank having a longitudinal axis, including a generally right cylinder shank portion and a tapered frusto-conical shaft portion at the work entering end of the shank portion; (b) forming three spaced flat portions on the blank extending longitudinally on the blank parallel with the longitudinal axis, terminating at opposite ends within the shank portion and the shaft portion; (c) forming a delta formed region at the head end of each of the flat portions, the delta formed region including a peripherally arcuate convex surface tapering gradually along its length to the flat portion; (d) thread rolling the blank to form male threads of width substantially less than the length of each of the delta formed regions on the shank portion and the frusto-conical shaft portion except a first length of the frusto-conical shaft portion at the work entering end thereof, whereby a second length of spoon-like recesses are formed on the crest portions of the threads passing on each delta formed region, adjacent ones of the spoon-like recesses having a same width and decreasing depth in the direction from the work entering end to head end of the screw.

Claim 9

A method of making a self-tapping thread-forming headed screw comprising the steps of: (a) forming a blank having a longitudinal axis, including a generally right shank portion and a tapered frusto-conical shaft portion at the work entering end of the shank portion, the frusto-conical shaft portion including a first segment contiguous with the shank portion tapered at a first angle with respect to the longitudinal axis and a second end segment longitudinally spaced from the shank portion and contiguous with the first segment, tapered at a second angle greater than the first angle; (b) forming three equiangularly spaced flat portions on the blank extending longitudinally on the blank parallel with the longitudinal axis, terminating at opposite ends within the shank portion and substantially at the boundary between the first and second segments of the frusto-conical shaft portion; (c) forming a delta formed region at the head end of each of the flat portions, the delta formed region including a peripherally arcuate convex surface tapering gradually along its length to the flat portion and having side edges such that the side edges and the edge of the delta formed region closest to the screw head, which bound the delta formed region, define an isosceles triangle; and (d) thread rolling the blank to form male threads of width substantially less than the length of each of the delta formed regions on the shank portion and the frusto-conical shaft portion except the second end segment thereof, whereby a plurality of spoon-like recesses are formed on the crest portions of the threads passing on each delta formed region, adjacent ones of the spoon-like recesses having a same width and decreasing depth in the direction from the work entering end to the head end of the screw.

Claim 10

A method of making a self-tapping thread-forming headed screw comprising the steps of: (a) forming a blank having a longitudinal axis, including a generally right shank portion and a tapered frusto-conical shaft portion at the work entering end of the shank portion, the frusto-conical shaft portion including a first segment contiguous with the shank portion tapered at a first angle with respect to the longitudinal axis and a second end segment longitudinally spaced from the shank portion and contiguous with the first segment, tapered at a second angle greater than the first angle; (b) forming three equiangularly spaced flat portions on the blank extending longitudinally on the blank parallel with the longitudinal axis, terminating at opposite ends within the shank portion and substantially at the boundary between the first and second segments of the frusto-conical shaft portion; (c) forming a delta formed region at the head end of each of the flat portions, the delta formed region including a peripherally arcuate convex surface tapering gradually along its length to the flat portion and having side edges such that the side edges and the edge of the delta formed region closest to the screw head, which bound the delta formed region, define an isosceles triangle; and (d) thread rolling the blank to form male threads of width substantially less than the length of each of the delta formed regions on the shank portion and the frusto-conical shaft portion except the second end segment thereof, whereby a plurality of spoon-like recesses are formed on the crest portions of the threads passing on each delta formed region, adjacent ones of the spoon-like recesses having a same width and decreasing depth in the direction from the work entering end to the head end of the screw.