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DaveInDenver
12-02-2009, 12:28 PM
I've been on again, off again trying to figure out a way to replace a couple of broken captured nuts on my truck. In this case they are also blind captured nuts, which means that getting into the location with a free nut is not difficult as a matter of convenience or speed, but necessarily impossible. Well at least practically, since removing the part is possible (it's bolted on to the frame) and technically possible to machine or/and weld something in there.

Specifically what happened was the two nuts where the bottom of my front skid plate bolt onto slipped their tack welds on the Rubicon. Everything seemed fine until the first time I tried to drop the skid plate and things just spun. So I managed to get the bolts out that time and the Budbuilt plate also used two backup holes in addition to the factory two. No biggie since those were sufficient to hold the plate in place.

Fat forward to now. I sold my Budbuilt plates and want to reinstall my factory plate. Whoops, no nuts in the cross member anymore. :doh:

Unlike the two backup holes on the Budbuilt, long bolts and fender washers aren't going to work.

This ends up being a major PITA because the cross member holds up the front diff, for one, and taking it off is fairly low on the potential repair scale, at least for the moment.

So I need some sort of insert or something that can be installed from the bottom that will accept a bolt. The cross member material is pretty thin (about 1/8"~3/16" thick). I tried just tapping the hole to 10mm, the next size up from the original 8mm bolts, but it's sized just big enough that there was almost no thread depth. Going up to a larger bolt crossed my mind, but first 12mm seems like major overkill and there's only enough thickness to support maybe one thread anyway.

Best I have come up with is what's called a Well Nut and a Jack Nut. Conceptually these are exactly what I'll probably need, although I am slightly worried that it's too light duty (and the Jack Nut requires some sort of special tool and just for 2 nuts that is not cost efficient). The stock skid plate is not all that heavy, so I think it would work just fine to hold it in place, but under use the force will be largely shear on the fastener and I'd can imagine the rubber wearing and tearing pretty fast.

http://www.emhart.com/images/img_WELLNUT_wSTInsert.gif http://www.emhart.com/images/img_pop_wellnut_ani.gif

http://www.emhart.com/images/img_jacknut2_000.gifhttp://www.emhart.com/images/img_pop_jacknut_ani.gif

POP also makes a blind rivet/nut that will probably be my first attempt. Again, think it needs a special tool and I'm gonna guess small number of piece buys are not common. But I think it holds the most promise in theory, although the POP gun to install it is probably not the same hand tool I use for little rivets.

http://www.emhart.com/products/pop/images/img_pop_popnut_000.gif




Any other ideas?

DaveInDenver
12-02-2009, 12:31 PM
Atlas also makes a common blind insert. Wondering about distributors for these things and cost. But OTOH, good enough for the Space Shuttle, probably work alright for Imelda.

http://www.pemnet.com/fastening_products/atlas/

SteveH
12-02-2009, 01:54 PM
I have used riv-nuts (rivet type nut inserts) and consider them fine for holding down a shifter boot, but not ok for a skidplate. The Well-nuts (rubber) seem doomed in this application, too.

Two ideas: Weld a short metric stud to the frame to hold the skidplate, or weld a nut directly to the frame on the bottom. With the former idea, the stud may get horked on a rock, and with the latter, your skidplate will be 'spaced down' an amount equal to the nut thickness. But, either one is cheap and stout for the job.

MDH33
12-02-2009, 02:06 PM
weld a nut directly to the frame on the bottom.


This might work. Drill the proper size hole. weld nut over hole. tap through nut into drilled hole. Bolt then passes through skid plate, nut and tapped+drilled hole.

DaveInDenver
12-02-2009, 02:12 PM
You make a good point and I agree about the POP parts. These Atlas (and similar, there's other companies) parts look a lot more promising. The rep forwarded me a performance databook and it looks like once set they can tolerate plenty high upset and torque loads. For example the 1/4" alloy steel ones will support about 1,000 lbs in tension without failing and are as strong as the bolt in shear. Looks like they are about a buck a piece, although I suspect that would be in lots of like thousands. Still looking into it, though.

Red_Chili
12-02-2009, 02:49 PM
If you can get to the backside, welding a new captured nut on is far preferable.
In cases where the backside is inaccessible, I have also drilled a hole large enough to pass the nut through... then stitch welded it into position whilst holding it in place with a bolt. The threads almost always need to be tapped after this.

But t'was grand in function.

(Channeling my Irish grandmother)

corsair23
12-02-2009, 04:45 PM
What about nutzerts or whatever they are called? The things that are required when you add an aux tank to an 80 for instance? Haven't done that yet so I don't know if they are strong enough...

I need something like the last pic in the first thread though to attach my hood shield/bug shield to the LX if anyone comes across a handy place to buy them :)

DaveInDenver
12-02-2009, 05:02 PM
What about nutzerts or whatever they are called? The things that are required when you add an aux tank to an 80 for instance? Haven't done that yet so I don't know if they are strong enough...

There are AFAIK two kinds of nutserts. Some are regular expanding for sheet (which is what those Atlas fasteners are that I link to in my second post) and the other are expanding inserts that require full contact along their length (similar to a masonry insert). Those are uber common in my field where the enclosure is aluminum for weight savings, but aluminum does not hold threads well. So they put in a stainless steel nutsert into a bore.

I am not familiar with the aux tank installs, but I suspect that if you need to put threads in a place on the frame that only has a hole then that is exactly what I am looking for. Got a reference I can check out?

jacdaw
12-02-2009, 05:43 PM
I have been a happy nutsert user for a few years. I get 'em from McMaster-Carr. The last use was to replace all the captured nuts holding the rag top bars/hinges to the side panels on my MGB. IMHO, stronger and more reliable than the original fasteners. They get quite a bit of side-load stress/leverage from cycling the top.

DaveInDenver
12-02-2009, 05:46 PM
I have been a happy nutsert user for a few years. I get 'em from McMaster-Carr. The last use was to replace all the captured nuts holding the rag top bars/hinges to the side panels on my MGB. IMHO, stronger and more reliable than the original fasteners. They get quite a bit of side-load stress/leverage from cycling the top.
Do you have the pliers to install them or is there a type that pulls snug with a bolt or something? I saw them at McMaster and they are cheap enough, but the installation tool is $60 up to $200!

jacdaw
12-02-2009, 05:53 PM
Do you have the pliers to install them or is there a type that pulls snug with a bolt or something? I saw them at McMaster and they are cheap enough, but the installation tool is $60 up to $200!IIRC, the tool is specific to the size of the fastener. Mine is the bolt type tool that compresses the 'sert and was not expensive. I tried to ease the pain of buy-in by getting a large number of fasteners -- which I never used all of :(. I wonder if the version with the cheaper bolt type tool is strong enough for the weight of your truck dragging on the skid plate?

nuclearlemon
12-02-2009, 06:19 PM
yes, there are special pliers required. i've got a cheap set of pliers, but doubt it would be strong enough to handle a good nutsert.

corsair23
12-02-2009, 06:24 PM
I am not familiar with the aux tank installs, but I suspect that if you need to put threads in a place on the frame that only has a hole then that is exactly what I am looking for. Got a reference I can check out?

Romer would be the one to ask...Not sure who else in the club has actually installed a sub tank in an 80...I recall back when reading Romer's sub tank install thread on MUD something about the nutserts and the cost of the installation tool being pricey...Might be something a few people could go in on though if several folks are looking at installing the same size?

farnhamstj
12-02-2009, 07:47 PM
On my old 40 I was able to reach in through holes in the frame and drop a bolt down through the hole that was long enough to then install washer and nut on the bottom of the skid plate. I could grab some extra treads with a vice grip and tighten the nut.