Written by Jody Muelaner
Pierce-clinch nuts, also referred to as self-piercing nuts, are permanently installed in sheet metal parts to provided a threaded hole. Other parts can then be bolted to it and easily disassembled as required.
These components can be used as a low-cost alternative to weld-nuts and, therefore, install without the fumes and sparks associated with welding. A weld nut is a type of nut that is specially designed to be welded to another workpiece.
Pierce-clinch nuts are self-piercing and require no hole to be pre-punched into a sheet or the workpiece. The nut is simply pressed in from one side, with a die on the opposite side. A central disc is sheared away, leaving a hole in the sheet where the pierce-clinch nut is pressed.
Once this installation is complete, the sides of the hole in the sheet deform into indentations in the perimeter of the nut — locking it into place in a clinching process. This is all carried out in a single operation that takes less than a second.
The typical installation tool use for this process has an automatic feed that can rapidly install many pierce-clinch nuts in quick succession. Pierce-clinch nuts provide a medium strength fastening and can be fitted into sheets varying in thickness from 0.6 to 3.5 mm. The nuts can be supplied un-plated or with various electro-plated zinc finishes. The nuts can also include a self-locking thread.
Other fastening processes that use clinching to join sheet metal include self-piercing riveting or clinch joining. Both of these permanently join two or more sheet metal parts to each other. However, pierce-clinch nuts only permanently join the nut into a single sheet metal part. Other parts can then be non-permanently bolted to it.
For example, self-piercing riveting uses a rivet that clinches the sheets as it is pressed into them. This is also a single operation process, that does not require a preformed hole. Clinch joining, also known as press-joining or clinching, is another way to quickly join sheet metal without the use of fasteners, welding, or adhesives.
Advantages of the clinching processes include a complete lack of fumes and sparks, no heating of materials, low noise, and low energy consumption. Pierce-clinch nuts can also be used for pre-coated materials that are not suitable for welding. One disadvantage is that access from both sides of the part is typically required.