The design challenge is to fasten thin metal sheets in a manner that assures load-bearing threads that are stronger than tapped holes. In addition, the fastening cannot protrude on either side of the sheet. One solution is the PEMSERT self-clinching flush nut. These nuts can be installed before sheet bending and forming to provide threads for mating hardware in sections that otherwise would be inaccessible for fastener installation after chassis are formed. Their hexagonal head and clinch technology ensures high axial and torsional strength in service. Ultimately, the nuts install permanently, will never loosen or fall out, and leave surfaces unmarred to enhance the functional and cosmetic qualities of assemblies.
The product line includes PEMSERT F 300 Series stainless steel types for installation into steel or aluminum sheets and PEMSERT F4 heat-treated 400 Series stainless steel versions specifically designed for installation into 300 Series stainless steel sheets. Both types are available in thread sizes #2-56 through ¼-20 and M2 through M6. Sheets can be as thin as 0.060 in./1.53 mm. For aerospace applications, F nuts can be ordered to conform with US NASM45938/4 aerospace standards.
Installation is accomplished easily by squeezing the nut into a round hole using sufficient force to embed its hexagonal head flush in the sheet. The metal displaced by the head then flows evenly around the back-tapered shank of the fastener to securely lock the nut permanently into place. Both the hexagonal head and the fastener’s self-clinching design combine to deliver high pullout and torque out resistances. Only a mating screw is required to complete final component attachment.
Filed Under: Aerospace + defense, Design World articles
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