Rivet Nuts

[MickinOz]

What's the group thinking on rivet nuts?
My new frame is 75 x 50 x 2.5mm rectangular hollow section.
I do not wish to drill through both top and bottom plates of the RHS to through bolt the floor.
I could weld on tabs, but I would prefer not to.
So, I was thinking about using rivet nuts.
10mm ~3/8 inch.

Then I'd only drill through the top plate.
So, do these things hold well?

 

[bdosborn-SMB]

Check out the pre-bulbed nuts (also called plus nuts). They have wings that expand to grip a bigger surface area behind the hole:

[fimg=400,200]https://www.pointsunknown.com/blog/wp-content/uploads/2016/10/cover-800x445.jpg[/fimg]


Plus Nuts

I just bought some and will be trying them out in the van. Riv nuts and plus nuts are super popular on the the van building forum.
Bruce

 

[Socal Tom]

I've used Riv-nuts on other projects before. Its not an awful idea. The things I would consider
1) What do you do if you get 1/2 the bolts tight, then you find a riv-nut that spins and won't tighten down? ( this has a 99% chance of happening if I do it, I just have that kind of luck )
2) What is the risk that the frame could rust, and weaken the frame where the riv-nuts attach? You won't be able to see/inspect that area. ( additionally, you will be creating a place for water to get in the frame, but it can't get out, so it would rust if it gets wet in there.( salt exposure would be bad).
3) Also, have you used rivet nuts before? It takes some effort to install them ( might be easier if you have the special tool, I did it the manual way)
Personally I think the tabs/bolt through methods are probably less risky in the long run.
Tom

 

[ddc612]

I prefer the tabs, or gussets, then bolt w/washer, and self locking nut. As far as moisture getting inside? I'd drill drain holes in the bottom of all enclosed frame members to prevent trapping water. So a teardrop should last many years.

Sent from my SM-G970U using Tapatalk

 

[bdosborn-SMB]

Just tried on of the plus nuts; pay attention to the grip range if you buy them.
Bruce

 

[twisted lines]

If i used one, I would tig weld it.

 

[PhilipE-SKO]

This style of attachments has been used for decades in semi's. Its a good fast way to secure items in thin metals. Easy to replace if you break a bolt off. Just take a 4.5" grinder and take the head off the rivnut/ nutsert. punch it out. Install the new one/ done.

I prefer the pop rivet style install tool. The manual way you have more issue with a mis-installed nut. With prices down in the $30 dollar range for a kit. Its not worth trying to hand set anymore.

Mick if your talking about a square box tube. Never threw bolt without installing a slug. A slug is a piece of round metal longer than the tube. You drill the slug down threw center for your bolt size. Then you drill your tube for the OD of the slug. Then weld the slug into the square box tube. This stops the tube from crushing when you tightening a bolt down.

I don't recommend drilling and tapping a slug. If you bolt rusts in or breaks off for some reason. Then your stuck with a broken bolt removal. Use a plain threw bolt. If it breaks. No big deal. Its a simple bolt that any hardware store will have.

 

[MickinOz]

Thanks for all the replies gents.
With regard to corrosion, my frame is a hot dip galvanised boat trailer, not anticipating too many issues.
As well, the longitudinals are open both ends and the cross members are drilled with drain holes ex factory.
It is a used trailer but there is plenty of the sacrificial zinc still on it.

If I were to through bolt the frame, I'd insist on anti-crush spacers (slugs) too.
One of the reasons for my reluctance to use through bolts is the messing about installing the slugs.
I'd prefer to slide them inside the tube, rather than drill for the OD and weld them in for this particular installation, but it would be difficult.

It was because I've seen these things used on truck chassis for many, many years that I thought they were worth considering.
If they can hold a 900 series Kenny together, surely they would hold an 8 x 5 wooden floor to a trailer frame, was my thinking.

Philip, do you agree the plus nuts would have better holding power than the rivnuts?

Still thinking.

 

[PhilipE-SKO]

I have not used any plus nuts. I have a large supply of rivnuts. I buy them in 100 round boxes. I might try them whenever I run out of rivnuts. LOL

In theory they should hold better due to the larger clamping area over a rivnut's smaller foot print.

 

[mnswamp]

I've used plus nuts on two suburbans to hold artificial rain gutters for mounting bike racks - and then put up to 10 bikes on top. I can also tell you that the day I wasn't paying attention to the low clearance sign and ripped the front bar off the top (no bikes thank goodness), the rack failed, not the plus nuts and fake gutters
As someone up thread mentioned, check the grip range.
I can also tell from experience that using a rattle gun to install seems to give a better fit than trying to install the things by hand. It's much easier to keep the appropriate pressure on the install tool, and a lot easier on your arms - especially if you have a number of them to install. BTW, order direct - the factory is extremely helpful.
One other minor item. What you give up with plusnuts is the ability to have a lock nut on the bottom. I would certainly use a little Loctite 242 on the threads even with a lock washer over the fender washer.

 

[saltydawg-TNT]

My opinion is NO. The issue is not the install or the bolt. Its two years down the road when the bolt is slightly rusted to the riv nut and you try to remove it. What happens when the bolt is more stuck to the riv nut than the riv nut is to the frame? Thats the problem with then, esp on a closed frame, you cant get to the back side to hold it so it just spins.

 

[swoody126]

My opinion is NO. The issue is not the install or the bolt. Its two years down the road when the bolt is slightly rusted to the riv nut and you try to remove it. What happens when the bolt is more stuck to the riv nut than the riv nut is to the frame? Thats the problem with then, esp on a closed frame, you cant get to the back side to hold it so it just spins.

saltydawg,

this is a double edged sword situation

rivnuts are specifically designed for places where you don't have nut access

decision time

sw

 

[JasenC]

Not a fan of them, I've run across enough spinners on stationary objects, not being drug down the hwy.

I'm going with screw on threadcerts from Rockler placed under my floor sheathing and bolted up thru framing from the underside.

 

[MickinOz]

I said "ah , bugger it" and welded on some brackets so I could through bolt.

 

[twisted lines]

Not a fan of them, I've run across enough spinners on stationary objects, not being drug down the hwy.

I'm going with screw on threadcerts from Rockler .

Haven't seen them !
Thanks TL

 

[gudmund-TNT]

for what it's worth, years ago when working for Boeing as a mechanic - was sent to Calif. on a factory assist. where we were building food galleys and we used a lot of rivet nuts. When using them, just as we would insert nut to press - we would use a bit of loctite as we inserted them around the edge, than do the pressing of it. I have always done them this way since (and have also used touch-up paint instead every so often when I had no loctite available)