Sheet Metal Thread Inserts

NickMaul

NickMaul

Well-Known Member
Joined
Jul 4, 2009
Location
Norfolk, VA
NC4x4,

I come forward searching for some technical guidance. Currently installing jb fab twin shifters into the floor of my XJ. As many people know the body sheet metal on XJs are gage 10 billion.



The pictured plate is 3/16" while not ideal it is the best piece I had laying around plus I needed something adequate to weld on to mount the shifter brackets to. I want to do four or six bolts fastening the plate onto the floor. Which way would be the best to keep this removable friendly?

I am thinking of trying rivet nuts threaded for a 1/4" bolt. I have given sheet metal screws a try in a few areas and no matter how careful I am the holes get trashed after a few cycles.

RRN_ACD.jpg


Is there another method that might work out better than rivet nuts?

TIA

Nick

:beer:
 
Those twist-resistant rivnuts in the picture will work fine (regular rivnuts aren't ribbed).

Rivnuts are about the cheapest and easiest to install thing that you can use for something like that. Well, except for the cost of an installation tool to go with them.

Make sure you spec the right type for the metal thickness that you need, etc. There are also closed and open ended options. Make sure you think carefully about sealing, as rivnuts sit slightly proud of the surface and can sometimes act like thin standoffs. Not a big deal if you use foam or cork that has enough compression height to conform to the sealing surfaces and the slight height of the rivnut.

You could also use weld nuts, or use a riveted nut plate. Neither of those options is as easy as a rivnut.

This all assumes that the floor is stiff enough to take the loads that you need, because all of the load is going to transfer to the floor through 4 or 6 discrete points around the edges of that floor cutout. If that's a problem, you may need to add a backer flange, etc., on the underside of the floor and then a rivnut may no longer be the best/easiest choice. It looks like the floor shape and stamping geometry is stiff enough for what you need though, if I'm guesstimating from that picture...
 
Fabrik8 said:
Those twist-resistant rivnuts in the picture will work fine (regular rivnuts aren't ribbed).

Rivnuts are about the cheapest and easiest to install thing that you can use for something like that. Make sure you spec the right type for the metal thickness that you need, etc. There are also closed and open ended options. Make sure you think carefully about sealing, as rivnuts sit slightly proud of the surface and can sometimes act like thin standoffs. Not a big deal if you use foam or cork that has enough compression height to conform to the sealing surfaces and the slight height of the rivnut.

This all assumes that the floor is stiff enough to take the loads that you need, because all of the load is going to transfer to the floor through 4 or 6 discrete points around the edges of that floor cutout. If that's a problem, you may need to add a backer flange, etc., on the underside of the floor and then a rivnut may no longer be the best/easiest choice.
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Good point about the standoff from the rivnut as sealing this entire combobulation will be key. Hopefully I can find some sort of gasket material or neoprene type rubber to help seal the gaps. Not really sure which type of rubber will be best for that :confused:

I see what you mean about using only 4-6 rivnuts. I am seeing I can get some from grainger in a pack of 25 so the more the merrier I suppose. The contour of the floor is by no means perfect but I will see if some more hammer treatment can get it to form and fit for a good seal and equal pressure on the majority of the rivnut/bolts.

I wanted to check and see what the minds of NC4x4 thought of my plan before I go drilling more holes in my floor :lol:
 
A foam sheet seal is probably the best you can do with that, or thick cork. Or, if you have enough flange width close to the cutout, a sheet rubber with a clearance hole for the rivnut head should work too. I'd still shy away from rubber though because the mating flatness will need to be much better than a thicker more conformable material.
 
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you could probably get away with a sheet of single sided sticky foam sheets from a craft store. there shouldn't be much of a gap. i would also rtv the seal if you really want to keep it tight but if its a wheeling rig id just use the foam
 
Where'd you get the bag o' rivnuts? I used special order 6-8 from Fastenal, when I was installing skidplates on XJ unirails.
Never used an official installation tool, I googled it and found the homebrew washer/spacer bolt combo.
 
RenegadeT said:
Where'd you get the bag o' rivnuts? I used special order 6-8 from Fastenal, when I was installing skidplates on XJ unirails.
Never used an official installation tool, I googled it and found the homebrew washer/spacer bolt combo.
Click to expand...

Those specifically came from a grainger store front local to me in VA.

I know the basic hardware stores don't carry them. $17 for 25. These are 5/16-18. Sufficient for just holding down a shifter plate.


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RenegadeT said:
Where'd you get the bag o' rivnuts? I used special order 6-8 from Fastenal, when I was installing skidplates on XJ unirails.
Never used an official installation tool, I googled it and found the homebrew washer/spacer bolt combo.
Click to expand...

McMaster Carr sells them. Lots of different flavors, open or closed, ribbed or not ribbed, floating thread, aluminum or steel, all the thickness ranges, all the thread sizes, etc.
Aircraft Spruce, Skygeek, Pegasus usually sell them too, and Coast Fabrication maybe. MSC should too. McMaster and Pegasus are usually my go-to places for things like that.

I order exactly nothing from Fastenal; they're useless unless it's something in local stock. If I need to order something, they're the last place I'd order from with all of the better/cheaper/faster choices.
 
Guys you can get a starter pack, fairly decent tool and case all through the devil....I mean Amazon.
Pay close attention to the rivited thickness as said. Done right the sleeve crushes on the backside of the base material only. Then sucks tight to the material. Anything else and it will spin or come through.
Err on a larger fasteners, thinner that 1/4 and you have to be very particular not to bend the tooling anvil.
Most tools are like pop rivit guns, so larger rivnuts can be hard to sqeeze. Access is also keen to track. Remember to tool has to fit, unless you do a bolt washer floating spacer affair to draw it up. Hands down unless you got a air gun to pull them any thing over 1/4 becomes a manual affair to squeeze em.
Larger verticle riv tools are available but need even more space to squeeze.

At least your not looking for Huck bolts like American Lafrance built fire trucks, and some airframes are built. Really unique tooling.........

On another note, a similar fastener is available for fiberglass that has a very wide flair. Works great for lighter clamping on like odd size, thick, or offset shoulder thickness on the back side. Most are aluminum and pull really easy to set. Another is a swelling rubber insert with a threaded inner sleeve usually brass. Great for blind fastening and dampening action at the same time. Work like a peg in a drilled hole, swell with fastener and done. Removable.
 
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Fabrik8 said:
McMaster Carr sells them.
Click to expand...

I eyed them and was in a mood to have them asap so I can get this done and move on to other things on my list so grainger to the rescue it was. Otherwise, yes mcmaster would have already had my order!
 
The Astro rivnut kit in the blue box is the one I went with after agonizing over which to get. Couldn't be happier for the money. Typically get my nuts from Amazon too. Uxcell brand. Cheap, but haven't had a failure yet. Since I got the tool, I find myself creating reasons to use it because it's so much fun.
 
NickMaul said:
I eyed them and was in a mood to have them asap so I can get this done and move on to other things on my list so grainger to the rescue it was. Otherwise, yes mcmaster would have already had my order!
Click to expand...

Order from McMaster before a certain time and it will arrive the next day in your area with ground shipping. There are Atlanta and New Jersey warehouses. We used to make a small order every day when I was working in Hampton/Newport News area back in the day.

How's the 757 these days? Traffic or car theft any better? ;)
 
Fabrik8 said:
How's the 757 these days? Traffic or car theft any better? ;)
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Traffic is so so. No car theft to speak of. Been here for two years and not really hustling to leave. I love the water as much as I love wheelin. It fits.


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