Rivet Nut vs PEM Nut When the Sheet Is Too Thin

Rivet nut vs PEM nut usually isn't a debate until a sheet comes in thinner than the nut's minimum. Then it gets real fast.

Can You Install a PEM Nut in Sheet Thinner Than Its Minimum?

Not properly. A self-clinching nut needs the sheet to cold-flow into its undercut, and if the shank pokes out the back, it can't seat. Pick a nut rated for that thickness, or switch to a rivet nut.

An r/engineering user had 14 ga 304 stainless and needed M6. The thin-sheet SP-M6-0 wasn't something they could buy, and the SP-M6-1 was a hair too thick for 14 ga, so the feature the sheet is meant to flow into would stick straight through. One reply said exactly that: the shank protrudes out the other side and won't press in properly. Others pointed to rivet nuts instead. One also warned that hardened clinch nuts and stainless sheet of unknown hardness are a bad mix, because sheet that's too hard won't flow.

The two rules for clinching

PEM's FAQ puts it simply. The panel has to be ductile and softer than the fastener, and it has to meet that fastener's minimum sheet thickness. Some types go into sheet as thin as .008" (0.2 mm), but PEM says .030" (0.76 mm) or .040" (1 mm) is the usual minimum.

Stainless needs its own types. PEM lists SP nuts and several others as designed for stainless sheet.

Rivet nut vs PEM nut: when the rivet nut wins

PEM's own one-side-access guide says threaded rivet nuts install from the front and give permanent threads in metal or plastic sheet as thin as .020" (0.50 mm). They also go into tubes and extrusions where you can't reach the back, and you can fit them later in the field. The trade-off is clearance. Setting one bulges its shank against the back of the sheet, and there's a head on the front, though PEM lists low-profile head styles. But you get threads.

For choosing among clinch types, see picking a PEM fastener for your sheet and PEM in galvanized vs cold rolled. If the screw head itself has to sit flush, flush screws in thin sheet metal walks through the options.

At DigiForge

We do PEM insertion in our sheet metal work. The sheet metal capability page lists our stock sheet, including Stainless 304 and Stainless 316. If your thickness is borderline, flag it on the drawing. Rivet nuts aren't listed there, so if you'd rather use them, ask us when you quote.