The fasteners were developed as economical and practical alternatives to bent tabs on the edges of sheets, bent flanges, right-angle brackets, or tack welds.
PEM R'ANGLE fasteners from PennEngineering Fastening Technologies, Danboro, Pa., includes both self-tapping and steel-threaded types, which install permanently in metal sheets as thin as 0.040 in. or 1 mm.
Self-tapping, Type RAA, aluminum clinch fasteners are used in aluminum sheets, requiring only a thread-forming screw in sizes #4-40, #6-32, #8-32, M3, or M4 to complete final assembly. Threaded, Type RAS, steel clinch fasteners in similar sizes can be installed in aluminum and steel sheets, and accept standard machine screws.
Installation involves a three-step process. First punch a properly sized rectangular mounting hole in the sheet. Secondary operations such as deburring are not necessary. Then place the fastener through the mounting hole and into an anvil. Finally, with punch and anvil surfaces parallel, the assembler applies a squeezing force until the bottom of the fastener becomes flush with the sheet.
Benefits include more-predictable assembly, improved shielding, material and assembly savings, less loose hardware, unmarred panels, and no welding.