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Distributor's Link Magazine Winter 2019 / Vol 42 No1


36 THE DISTRIBUTOR’S LINK PENN ENGINEERING 5190 Old Easton Road, Danboro, PA 18916 TEL 1-800-237-4736 FAX 215-766-0143 EMAIL WEB SELF-CLINCHING LOCKNUTS HOLD MATING SCREWS TIGHT by Michael J. Rossi, Marketing Services Supervisor When fasteners are subjected to disruptive application-related forces – vibration, thermal cycling, or others – their reliability in service may be jeopardized. Mating screws particularly become targets for loosening and potential attachment failure. Self-clinching locknuts offer solutions on multiple fronts. These fasteners effectively “self-lock” the threads of mating screws to eliminate any risk of screws loosening over time, regardless of application forces. And, unlike chemical locking methods or patches, locknuts do not require extra production steps and/or materials during the assembly process, saving time and money. Beyond the central function of withstanding external forces and holding mating hardware securely, self-clinching locknuts offer yet another layer of reliability, thanks to self-clinching technology. Upon their installation, the locknuts become permanent and integral parts of a thin metal assembly, will not loosen or fall out, never have to be restrained from rotation with a tool, and never have to be handled again. Specific types of self-clinching locknuts carry specific benefits, based on design. Some integrate floating threads to compensate for misalignment; miniature versions feature smaller footprints accommodating smaller design envelopes; and others will achieve particularly high clamp strength. The universe of self-clinching locknuts continues to expand in response to application and marketplace needs. Self-clinching locknuts are available in two primary categories: prevailing torque locknuts (in many variations) and free-running types. Self-clinching prevailing torque locknuts encompass all-metal styles as well as locknuts integrating plastic inserts (usually nylon). All-metal types “self-lock” the threads of mating hardware by fundamentally altering the shape of the nut THE ENTIRE FAMILY OF AVAILABLE SELF-CLINCHING LOCKNUTS. during manufacture to grip a screw during tightening. A common method is the purposeful distortion of the nut’s threads. Depending on type, the nut’s threads may be elliptically squeezed (slightly deforming the thread barrel into an elliptical shape), flexing jaws may be created by vertically slitting the thread barrel and squeezing the two sections together, or one or two of the last threads on the head side of the nut may be deformed. The particular design feature of all-metal prevailing torque locknuts produces friction between threads of mated hardware, thereby increasing the force needed to tighten as well as loosen the nut. All-metal prevailing torque locknuts maintain essentially the same torque value, regardless of the amount of axial load applied, and have been engineered to provide up to 15 cycles of thread-locking performance. Self-clinching prevailing torque locknuts with nylon inserts generate torque resistance using a plastic insert as the locking element. The insert is added during manufacture into the selfclinching body of the nut on the screw exit side (with the inner diameter of the insert approximately at the screw pitch diameter). TECHNICAL ARTICLE CONTINUED ON PAGE 116


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