Research Engineering & Manufacturing, Inc.

Research Engineeering & Manufacturing, Inc.

Barry J Hughes

A fastener has multiple secondary threads intertwined with a primary thread installable in a thermoplastic workpiece. A method and die are arranged for fabricating such a fastener. The fastener comprises a threaded shank portion having a primary thread of a desired form and a driver head attached thereto. At least one secondary thread is intertwined with the primary thread. In accordance with one embodiment of the invention, an outer surface of the fastener may be heated to a preselected Curie temperature during the installation of the fastener into a workpiece. The preselected Curie temperature enhances the flow of the thermoplastic material around the fastener while the fastener is being installed in the workpiece. A coating material having a particular desired Curie temperature may be applied to the fastener to produce desired driving characteristics. The heating of the fastener through Curie temperature heating reduces the drive torque and promotes plastic flow of the thermoplastic around the fastener without adversely affecting the physical characteristics of the thermoplastics material. Rolling dies having a novel rolling face are used to produce the fastener in a single rolling operation such that the formation of the primary and secondary threads can be accomplished without the one interfering with the other during formation.

Threaded fastener for use in thermoplastics and roll die for producing

A thread-forming fastener and method of installation thereof are provided for use with a workpiece constructed of a thermoplastic material. The fastener includes a threaded shank having a thread of desired form and a driver head portion. A metallic coating of a predetermined composition is applied to the threaded shank. The composition of the coating is selected for its effective Curie temperature for heating the fastener during application of the fastener to the thermoplastic workpiece. The heated surface enhances plastic flow of the thermoplastic material during thread forming and effectively reduces the required drive torque for thread forming by the fastener while increasing the holding torque. The fastener is preferably also formed with a spaced thread defining an unthreaded surface portion running adjacent to the thread at substantially the root diameter of the thread. At least one radially outwardly extending ramp-like ratchet tooth is formed in at least one part of the unthreaded shank portion oriented for resisting rotation of the fastener relative to the workpiece.

Fastener for thermoplastics

A blank and fastener formed from the blank for a thread-forming fastener which provides axially aligned driving. A tip portion of the blank is formed in a conical shape at an oblique angle to the shank portion of the blank. The blank formed as such is then formed with threads, however, the tip portion is formed with threads only about a portion of its outer surface. The resulting threaded fastener forms threads on an inside surface of a pilot hole in a workpiece in which it is inserted. The threaded fastener so formed minimizes driving effort and maintains proper alignment when the fastener is initially inserted and driven into an unthreaded pilot hole in a workpiece and also prevents cross-threading when the fastener is removed and reinserted into the workpiece.

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Wickford, RI, United States of America

Barry J Hughes