Adding threaded fasteners to uniframe?

If a guy were wanting to bolt such an item as a skid plate to his uniframe, what would be the best option for adding a threaded attachment point?

Options I know of or have tried in the past:

1. Fishing a nut-strip or plate with a nut welded to it into the uniframe. That seems way more annoying than it should be, as a nut-strip is out of the question in the belly area (no way to get it in there without cutting). A small plate (or nut with a tab on it so it can't spin) can be fished in through one of the clean out holes. But this seems like it would lead to more issues down the road, as a skid-plate tends to need to be removed for servicing of other components, and you'd probably have to re-align your nut every time you did this.

2. Rivnuts. I have no idea if you call them rivnuts - that's what they're called in aviation. You simply drill a hole the size of the rivnut, insert rivnut with pulling tool attached, pull rivnut (it expands like a rivet) and now you have a threaded insert. The problem with them is most of them are aluminum (easy to pull/manufacter and work well on aluminum structures) and really offer limited strength. Also, they have a tendancy to spin as they get old, which leads you to having to grind the head off the bolt that is in them (or drill it out if it's countersunk), then drill/punch the remainder out. This sucks, I do it enough at work. I can source steel rivnuts, but they are a PITA to pull (the tool is much harder to find and use) and they're even worse if they spin.

3. Anchor nuts. Again, aviation thing. They're simply a nut attached to a plate, the plate has two #40 or #30 holes in it so it can be rivetted in place so it won't move/spin. I think it'd be a horrible thing to try to install these things without cutting a large access hole somewhere. I do like them otherwise, they rarely cause trouble once installed correctly.

4. Drilling some fair sized holes in the frame where you want your attachment points. Then welding nuts to a peice of flat-bar or other steel to be installed on the outside of frame, with the nuts in the holes that you drilled previously. Best used in conjunction with the installation of frame plating or other reinforcements. This works alright, but it was a bunch of work and did require me to plate the frame. Having to plate the frame isn't all bad, but it's not what I'd like to do at this point.

5. Drilling holes through the uniframe, installing sleeves, and bolting through. Obviously this works better if your bolts are to be installed through the side of the frame. A guy reasonably has to weld the sleeves in if he wants the holes not to get wallowed out. I've never really done this.


So, what options am I missing? Is there any other easy or crafty ways? I'd appreciate any thoughts, as I want to do a full belly skid, and I'd like it to go as easily as possible.

I guess it depends on what you're mounting and how it will be used. For skidplate that are intended to take major hits, my preference would be anchor nuts where you have room and then rivet nuts with welded edges. I would not trust the thin unirail to hold a welded nut, but it can handle being sandwiched between two pieces of metal alright. BTW you can get steel nutcerts/rivnuts from McMaster, and you can use a sized bolt with oversized nut to compress it with hand tools pretty without buying the super dooper tools.

Look into "AVK"s if you have access to an air compressor. You simply use a air powered gun to insert nutserts into a pre drilled hole. They are easily stronger than the material surrounding the nut.

ehall said:

I guess it depends on what you're mounting and how it will be used. For skidplate that are intended to take major hits, my preference would be anchor nuts where you have room and then rivet nuts with welded edges. I would not trust the thin unirail to hold a welded nut, but it can handle being sandwiched between two pieces of metal alright. BTW you can get steel nutcerts/rivnuts from McMaster, and you can use a sized bolt with oversized nut to compress it with hand tools pretty without buying the super dooper tools.

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X2,it depends on the "loading"! Example:skid plates usually need nothing more than to hold them in place! Nutcerts are also available in stainless steel.

RCP Phx said:

X2,it depends on the "loading"! Example:skid plates usually need nothing more than to hold them in place! Nutcerts are also available in stainless steel.

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Well, duh. I could hold a skidplate up with 4 aluminum rivnuts in a -3 (10-32) size if I wanted to. It wouldn't survive being hit though.


The 'steel' ones that I get from work are actually stainless, and no, you can't pull them without the correct tool. The AVK ones look interesting, with the knurl to prevent them from spinning. But for what that would cost (them, a driving gun, shipping), I'm not inclined to go that route. In a similar concept, the aluminum ones I can get from work have a key on them to stop them from spinning, they work well other than you have to file a little keyway into the hole - which creates a stress riser. I'd definatly not use them for anything structeral. Nor would I use the style without the key. Plain steel ones would probably work fine, as long as I used 1/4" ones and ran 2 rows pitched ever inch or inch and a half down the entire area of the uniframe that I can use.

My actual intended use is nothing too crazy. Just a 1/8" 7075-T6 aluminum skidplate with 1/4" UHDP screwed onto the bottom. It'll be supported off the tranny crossmember and the frame rails, and maybe another couple places. 1/8" aluminum is pretty thin for a skid plate, even with the plastic on it, so it's not like I'm intending for it to see hard use. It's actually more of an expirament to see how well it holds up. 7075 is pretty tough though.

I also might need to attach some link brackets. I'm leaning towards sleeves and bolts for that. Or just welding them on like I normally would.

I installed a "panzer plate" (a skid plate) on my tdi VW jetta, (yeah I know its not a jeep) using supplied steel rivetnuts (nutserts), and wow, it was super easy. it also worked very well. the key is not to over torque them, it can cause them to slip. After using them for the jetta I picked up a light duty aluminum nutsert kit with install tool from harbor freight. I use it for all sorts of things on my motorcycle, jeep etc.

nice thing about steel nutcerts is that you can weld the outside lip to the sheetmetal if you want

byron555 said:

I installed a "panzer plate" (a skid plate) on my tdi VW jetta, (yeah I know its not a jeep) using supplied steel rivetnuts (nutserts), and wow, it was super easy. it also worked very well. the key is not to over torque them, it can cause them to slip. After using them for the jetta I picked up a light duty aluminum nutsert kit with install tool from harbor freight. I use it for all sorts of things on my motorcycle, jeep etc.

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My HF one didnt even make it thru the day.Now Ive got a Real" HD one that goes up to 3/8",well worth it!