Rivnuts (AKA nutserts, and other names) are a type of ‘blind fastener’; that is, they can be fitted through a surface without access to the rear of that surface, unlike, say, a nut an bolt, where you need access to both sides to fit and tighten the nut. The van is full of such surfaces, in fact almost every metal part you’d want to attach something to has no access to the rear surface.
Rivnuts are installed by drilling a hole (e.g. 9mm for an M6 rivnut), inserting the nut with a rivnut tool, and using the tool to compress the rivnut around the hole.
That leaves you with a threaded hole securely mounted to your sheet metal surface, into which you can fit bolts to secure furniture, cladding, and other substantial stuff in the van.
You could say a self-tapping screw is a kind of blind fastener – you just screw it in from one side – but so far, my experience has been so-so. I find they can easily be overtightened, and shear the threads they’ve just cut. Whereas rivnuts are satisfying to install, can tolerate endless removal and reinsertion of the bolt, and add a level of utility to sheet metal that is almost magical.
I’ve found a couple of them, just things to be aware of (we’ve had 2 failures out of maybe 100 rivnuts we’ve used, and we’re new to this):
- Installing: Spinning nuts. If you don’t tighten the install tool enough, the rivnut can be left a little loose, and then it tends to spin in the hole when you tighten a bolt. You can tighten up a rivnut that’s spinning, which seems to work fine.
- Planning: Finding the hole. Unlike screws, you can’t just drill through the workpiece and the mounting surface in one go. You have to make a hole for the rivnut, install it, then offer up the workpiece, fit the bolt through a hole in the workpiece and hope that the hole in the workpiece lines up with hole in the rivnut. Because the rivnut is fitted perpendicular to the metal surface, and has a precise thread, there is no room for slop. You can drill through the workpiece with a bit sized to your bolt (e.g. 6mm for an M6), and carry on through the metal to create a pilot hole for the rivnut, but this still has to be widened out to take the nut (in this case, to 9mm).
Top tips for rivnut happiness
Steel, not aluminium. Aluminium is softer, so I guess they’re easier to install, but we have no problems wit the steel ones, and they’re more likely to retain their thread when using steel bolts. I use the plated carbon steel (CR3 or BZP) not the more expensive stainless steel rivnuts.
Cylindrical, not hexagonal. You can buy rivnuts with a hexagonal external profile. The hexagonal nuts give ‘high torque resistance‘ (i.e. they’re less likely to spin, but I found them impossible to install in round holes in the 1-2mm steel sheet of the van. The splines on the round rivnuts seem to provide plenty of resistance for our usage.
Standard head, not low-profile. The head protrudes above the surface of the sheet metal, which prevents a flush fitting of the workpiece. But I found that this could be easily overcome by countersinking the hole on the rear of the workpice to accomodate the head of the rivnut. The payoff is that the standard head makes for better load bearing.
Use a good tool. I bought a proper rivnut tool, which was not too expensive, and works fine for the M5 and M6 steel rivnuts we’re using – it should go up to M8.
We’ve bought from several sources, but I’d recommend these:
£3.60 for 50 x M6 rivnuts from Memfast.