Thread-forming screw with tri-roundular, tapered end

Details Thread-forming screw with tri-roundular, tapered end Thread-forming screw with tri-roundular, tapered end

1993-07-02

1995-03-07

Wilson, Neill R.

Expanded, threaded, driven, headed, tool-deformed, or locked-thr

Externally threaded fastener element, e.g., bolt, screw, etc.

Pilot end having means enhancing fastening or installation

411416, 411421, F16B 2500, F16B 3504

Patent

active

053951956

ABSTRACT:
A thread-forming screw includes a tapered end portion having a tri-roundular cross section with three spaced flats and three threaded, round portions disposed in an alternating manner about the screw's periphery. The screw is formed by inserting a tapered blank between paired dies each having threads provided with undulations along their lengths corresponding to the circumference of the screw blank so as to form a trilobular thread on the screw which spirals around its circumference from one end of the cylindrical, untapered portion of the screw to the other in a direction opposite to that of the threads. While the untapered portion of the screw is provided with fully crested threads, the tapered end portion includes partially formed, or somewhat flattened, threads. The three spaced flats on the tapered end of the screw provide relief from contact with the workpiece into which the screw is driven for receiving deformed portions of the workpiece as the screw is driven into a workpiece aperture. The relief gaps, or pockets, facilitate driving the screw into the workpiece while ensuring a high strip force. In a preferred embodiment, the tapered end of the screw has 2-3 pitches, while the flats extend 3-4 pitches from the end of the screw.

REFERENCES:
patent: 3295154 (1967-01-01), Watson et al.
patent: 3455360 (1969-07-01), Simons
patent: 3800585 (1974-04-01), Simons et al.
patent: 3818749 (1974-06-01), Yankee et al.
patent: 3850074 (1974-11-01), Simons
patent: 3868871 (1975-03-01), Yankee et al.
patent: 3878759 (1975-04-01), Carlson
patent: 3918345 (1975-11-01), Phipard, Jr.
patent: 3934444 (1976-01-01), Simons
patent: 3945272 (1976-03-01), Simons
patent: 4315340 (1982-02-01), Veldman

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