Press-Fit Nuts

I'm finishing up summer maintenance on my Thiokol Imp (1404) and have a question regarding the hardware that holds some of the panels together. I have 1/4-20 hex head screws securing the access plates on the bed (covering the fuel tank & driveline) and below and in front of the engine. As best I can tell, there are press-fit nuts on the back side that the screws fit in to. About half of these nuts are stripped out, so to date I've been getting by w/ only a few screws holding the access covers in place. I'd like to do a better job of securing them, but am not sure what hardware to use. McMaster-Carr sells the appropriate press-fit nuts, but says that you need an arbor press (w/ access to both sides of the panel) to mash them into place. Is there a better way to do this? Clip-on nuts might work for the aluminum panels on the bed, but I don't think they'd do the trick for the engine panels. Suggestions?

Thanks

Ron

You can try to fix the ones you have, place a nut on a bolt with a washer
Thread in tighten nut with wrench. Sometimes it will tighten enough

Rivnuts like MNoutdoors mentioned. Very common in aviation.

Another term for these fasteners is Nutserts.

We've used them a fair amount on our snow cat projects, and so far anyway, like the results. On Thundercat we built all new floors and we also built an aluminum enclosure for the six-way blade's in cab control valve.

Tucker used a lot of small hex-head self drilling screws to secure the floor panels. When trying to remove them - a fair amount break off. (The best way to remove them we've found is to use a cordless 1/4" impact gun and feather the trigger lightly so it pounds away at the fastener without putting so much torque on it that it breaks.)

While most of the floors are riveted together, we wanted to be able to remove the floor sections on top of the transmission and the valve enclosure, but wanted a better solution than self drilling/tapping screws or rivets. We do nut have one of those big setting tools but rather a hardened serrated washer, a nut and socket head capscrew of the correct size.

View attachment 130808

We used larger Nutserts in some other applications such as securing the radiator support brackets to the frame.

'Rivnuts' -- thanks. Looks like McMaster-Carr calls them "Rivet Nuts". I'll get some steel ones for the engine covers since they're set in angle iron and aluminum ones for the back deck. I'll need to drill out and/or chisel off the old nuts (that are remaining), but that shouldn't be too difficult. Thanks also for the Amazon link to the installation tool -- yet another addition to my "unusual tools" collection.

a caution on nutserts use the steel ones not the aluminum inserts if you want to take them apart again.

I've done a fair bit with this style. I like the stainless steel ones for dissimilar metals. I have used aluminum ones, but, like Don implied, you have to use anti seize and then use a lock washer for holding.



"waste" a couple to see how setting them feels. My tool will strip the threads out of the stainless ones if I'm not paying attention.

I have used both the steel ones and the alloy..
The steel ones USUALLY have splines the swage into the metal and prevent them from turning later.

Always add a touch of never seaze to the threads on the bolts too.

The "NUT SERTS" ARE DEFINITELY HANDY.......

Avoid the ones that depend only on the clamping force of the sert to hold tight when loosening the bolt....Lest thy be cutting the bad boy out later on....and that is never a fun task.....

Depending on where you are installing them the spring steel units like what is used in the auto industry are a sweet deal and come in various styles, sizes and shapes..

Along an edge they are the catsass...

See piccy

I whap mine out with a air chisel.

Put a nut and bolt on them.

tack weld the nut

remove bolt.

fixed

If there is flooring to hide this , I just re-drill a hole next to the failed one and tap the angle.

On the dog house and thin stuff I found a bag of the spring type nuts in the image just above this message. I glue the bitches in place with tiny bit of silicon.

Great suggestions. This morning I received packages from Amazon & McMaster-Carr w/ rivnuts, an installation tool, and the proper drill bit. Working underneath the cat is awkward, but fortunately, I have it on a roll-around dolly during the off-season and that provided enough height to get to the bottom-side. The rivnuts went in pretty much as expected and for the first time I've got a full complement of screws holding the engine's access plate on. I need to order some stainless steel ones for the aluminum deck and will get to that next week.

Here's the first few rivnuts installed and a few other holes drilled out and ready for rivnuts:

View attachment 130844

And here's part of the access plate w/ lots of shiny new hex-head screws holding it on.

View attachment 130845

Again, thanks for the help with this.

Ron

Rivnuts are a pain in the butt! Not right now but in a couple years after wet and muddy and a little corrosion you will be getting the screw out with a chisel. The screw will stay and the rivet will turn. Redsqwrl has the best idea. Just my 2 cents.

We use a dzus fastener system pretty exclusively in the offroad community - just an option to look at

Check out "GRIPCO Nut Plates" Not savvy enough to post a picture from the internet yet, sorry. They're a great product. We use Nut Plates on all the airplanes where the nut is inaccessible. The ones we use are riveted in though. These can be spot welded.