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US 4,069,730 AGranted
Thread-forming screw
AssigneeWales-Beech Corporation
InventorCharles E. Gutshall
Life of this patent
Estimating the term…
Abstract
An improved thread-forming screw has a circular threaded main body portion and a tapered lobular pilot or thread-forming section comprising a plurality of transverse elongated projections or lobes on a circular conical core, each lobe having a sharp ridge running the full length thereof. The sharp edges on the lobes minimize the torque required to form threads in a workpiece, while the circular main body portion maximizes the holding power of the screw in the workpiece.
Claims7
A thread-forming screw comprising:
- an elongated shank including a substantially cylindrical main body portion having a continuous thread formed thereon;
- means at one end of said body portion cooperable with a tool for turning said screw;
- a work-entering tapered thread-forming pilot portion at the other end of said body portion;
- said pilot portion comprising a conical core having a substantially circular cross-section and a plurality of elongated tapping lobes extending outwardly from the surface of said core, each of said lobes having a sharp, fully formed outer ridge along its entire length, the sharp outer ridge on each of said lobes beginning and ending at the juncture of said lobes with said core;
- said lobes being disposed transversely on said core and spaced so that the outermost point on each of said sharp lobes falls on a helix having the same pitch as the thread on said main body portion and a diameter which increases from a minimum at the work-entering end of said screw to a maximum at the juncture of said pilot portion and said main body portion.
2 more elements
Dependencies are inferred from the claim text.