Our proprietary high-performance thread-forming fasteners are all designed to generate threads in non-threaded nut members; however, on occasion, these products are driven into threaded nuts or components. These situations typically result in inquiries about how our TRILOBULAR® fasteners perform in threaded nut members.
TAPTITE® fasteners are essentially made to tap dimensions. Therefore, when installed in a threaded hole, there is usually some prevailing torque experienced, as the fastener may have a minor amount of pitch diameter interference. It is possible that with a tapped hole on the maximum dimension and the TAPTITE® fastener on the minimum dimension, the screw could freely spin into an existing thread, but generally some prevailing torque is experienced.
Note that many end-users have a concern that a TAPTITE® fastener will try to form a new thread in the second installation. With a thread-cutting screw, this concern is valid, because the sharp cutting edge will likely dig into the sidewall and start a new thread. TAPTITE® thread-rolling screws, with their inherent tapered lead, take the path of least resistance and follow the already-formed thread. We have inserted TAPTITE® fasteners into threaded tensile test fixtures in our lab using a power driver and without hand starting the bolts, yet we still did not experience any cross threading or other problems.
Great examples are several seat belt bolt applications which were changed from machine/metric screws into tapped nuts to TAPTITE® products into unthreaded weld nuts, at mid-product cycle, caused by severe cross threading problems. In these situations, it is usually not the case that the TAPTITE® screws and the un-threaded weld nuts arrive on the assembly line at the same time. More often the TAPTITE® fasteners arrive first and the phase-in of the un-threaded weld nuts follows afterward. General Motors employed this short utilization of TAPTITE® bolts into threaded nuts many years ago when they gradually switched all their auto assembly lines to TAPTITE® seatbelt bolts over a 6-month time period. A similar approach was employed by Ford Motor Company and Chrysler (now FCA). With the Chrysler autos, a cross-threading problem was cured by using TAPTITE® bolts, even before the un-threaded nuts were introduced to the assembly line. In one application, Chrysler delayed completing the switch to un-threaded nuts, preferring to wait until the auto model was changed. Chrysler was well satisfied with this temporary utilization of TAPTITE® bolts, saving an estimated US$1,000,000 in repair work annually. We concluded long ago that installing TAPTITE® fasteners into threaded holes presents no problems and therefore, is a useful technique during the transition when switching from pre-threaded to un-threaded nut members.