Rivnut Tool

[Foster]

I'd like to hear the results of the pullout test on the 1/8" bar where you don't think the nut really set well. It looks like it expanded enough to keep it from pulling out.

Thanks for giving up your holiday for Science!

[bowmanb]

I have extensive experience with rivnuts from one of my former lives as an instrumentation installer. They work great with proper installation and care, but I have always been reluctant to introduce them to our FRC team because of this one problem-

If you ever manage to break one loose in a blind hole it can be a real bear to get the screw out of the hole.

The odds of this happening increase as the odds of incorrect installation increases. When I finally broke down last season and introduced them (our chassis design last year made our bumpers hard to attach/detach without them) I trained a special crew to use them and I demonstrated the spin-out problem and how to avoid it. It requires a combination of correct installation of the proper size and avoiding over-torquing the fasteners (I find that often teenage boys don't know their own strength!).

[PVCMike]

We have used riv-nuts also called nut-certs (or nut-serts) on 1058 for years. Really helps with fast repairs in the pit!

Step one is get the right tool. We have one similar to this which works MUCH better than the ones that look like a pop-rivet gun: https://www.amazon.com/Astro-1442-Th.../dp/B003TODXQW

Step two is to make sure you have the correct size drill bit. These things are sensitive to hole size so we double check we are using the correct drill every time.

As others have mentioned installation and placement is critical. We almost always have mentor supervision/help when installing any riv-nuts. They are also prone to under and over torquing so we usually teach a few students how to do it properly and supervise closely, or have a mentor install if necessary (with student help of course.) It helps to do some testing on a scrap piece to make sure your tool adjustments are correct.

We have run into situations where they come loose due to install error or just unexpected load and have had success drilling them out, although it's not fun. I would not recommend using loctite on the hardware you're placing in them, and if you do, very sparingly.

I would be interested in a part number or link to a pneumatic tool for installing these. We use a pneumatic pop-rivet gun and it's awesome.

[Chris is me]

I vastly prefer riv-nuts to PEM nuts. PEM nuts have an awful tendency to fall out if mishandled, and because of that I don't really trust them. Once a riv-nut is properly installed, it has a much harder time coming lose. This is just my experience - both solutions are valid. But I don't think PEM nuts are almost ever preferable for me.

[Fusion_Clint]

Ok,

Having never used a rivnut before, I started looking on youtube and came across this. https://youtu.be/3Og-tHIR_0I?t=66

For those of you that have rivnut experience, what are the cons of using this method?

[dradel]

Time. Takes a while to do that method. Also the chance of pulling the threads out of the nut is greater.

If only doing a few no big deal.

[RoboChair]

Originally Posted by Fusion_Clint

Ok,

Having never used a rivnut before, I started looking on youtube and came across this. https://youtu.be/3Og-tHIR_0I?t=66

For those of you that have rivnut experience, what are the cons of using this method?

Installation is time consuming and rather annoying. Anything larger than a #10 rivnut takes some considerable muscle and/or the use of a cheater bar(s).

[ollien]

Originally Posted by Jon Stratis

We've always used a wrench-driven tool, McMaster PN 96349A380.

Does this work for the non-self aligning rivet nuts?

[GeeTwo]

Initial results of rivnut pullout testing: (Due to budget constraints, only doing 10-32 steel thin-wall large flange inserts this year; if we're happy with the results, we'll expand our options next year).

I drilled a 19/64" hole using a drill press and inserted an SKL 10-32-130 steel thin nut with large flange into each of three pieces of aluminium:

• 3/4" x 1/8" bar (Ace Hardware, looks like 6061, pictured above)
• 0.1" wall Vex 1"x1" tubing (I used a factory hole as a pilot)
• ~1/16" wall channel (sold as 1/2" plywood edging, also pictured)

I then centered a 1/2" hex nut over the rivnut (large enough hole for the rivet to pass freely), added three steel 1/16" thick fender washers, and inserted a 1" stainless 10-32 cap screw (allen drive). I did not have a 3/8" to 1/4" adapter handy, so I could not use my torque wrench, so I used my shortest 1/4" ratchet driver. In each case, I tightened with my index finger and thumb against the adapter socket. In each case, I was using roughly the same amount of torque (to within perhaps 50%) at failure. I shall repeat these tests with an adapter so I can measure torque, and with the longer rivnuts in coming days.

Each setup reached normal (tee-handle) torque with no noticeable deformation or stress relief (that is, yielding or breakage) of any part. On applying additional torque to failure, each case had a somewhat different failure mode. Consult the attached image for clarification.

1/8" bar - the bar did not noticeably deform on a large scale, but the small crimped area of the rivnut reamed its way through the aluminum to a depth of about 0.1" (I was able to put the versaframe tubing wall between the stock and rivet flange with no difficulty) when the machine screw sheared at the head end of the threads. Because the failure was through reaming not bending, I expect that if the force had not been applied normally to the surface, far less force would have been required to pull the insert from the material. I definitely intend that we shall use the longer .225 rivets for aluminum of this thickness. In steel, it is entirely possible that the stock would have held the rivnut to a rather greater pull out force.

0.1" Vex tubing: The crimped area of the rivnut was adequate to hold in the aluminum. However, the wall of the tubing was deformed (volcano style) until the hole was large enough for the insert to be pulled completely clear of the tubing. It appears that a longer rivnut would provide minimal additional capacity, though I shall test this when the longer inserts arrive.

1/16" plywood edging: The aluminum yielded "volcano style" to a height of 1/16" on one side and 7/64" on the other, then the machine screw broke at the top of the treads on the insert, presumably from the bending torque.

Curiously, the VF thick wall tubing deformed much farther than the hardware store grade aluminum bar and plywood edging.

Edit/Addition:

Originally Posted by Fusion_Clint

Ok,

Having never used a rivnut before, I started looking on youtube and came across this. https://youtu.be/3Og-tHIR_0I?t=66

For those of you that have rivnut experience, what are the cons of using this method?

Originally Posted by RoboChair

Installation is time consuming and rather annoying. Anything larger than a #10 rivnut takes some considerable muscle and/or the use of a cheater bar(s).

I will add testing this method (with 10-32 thin wall steel inserts) to my next round of tests. It seems to me that you can get better torque with hex head bolts 1/4"-20 and larger than with any normal #12 and smaller heads. I am also concerned that applying torque to the threaded part of the insert during the crimp might result in a weaker/twisted crimp.

[cbale2000]

Not to get too off-topic, but as someone who had never even heard of Rivnuts before seeing this thread, I'm curious... What are the actual benefits of using a Rivnut? Most of the application examples I've seen so far look like it would have been far simpler and faster to just use a regular bolt+locknut.
You don't appear to be saving space since the rivnuts still stick out, and for that matter the rivnuts also appear to create an additional space on the front side of the material that wouldn't have otherwise been there.

Am I missing something here?

[Ari423]

Originally Posted by cbale2000

Not to get too off-topic, but as someone who had never even heard of Rivnuts before seeing this thread, I'm curious... What are the actual benefits of using a Rivnut? Most of the application examples I've seen so far look like it would have been far simpler and faster to just use a regular bolt+locknut.
You don't appear to be saving space since the rivnuts still stick out, and for that matter the rivnuts also appear to create an additional space on the front side of the material that wouldn't have otherwise been there.

Am I missing something here?

The way I understand it, the point is that the nut stays there when you remove the bolt, so it's better if the nut would be in a hard to reach position. Essentially, it lets you tap a threaded hole into a piece of sheet metal that would otherwise be too thin to tap.

My team has used rivnuts a few times in the past. This year we used them to attach our main breaker because the frame member we wanted to attach it to was surrounded by other components so we couldn't get a wrench behind it to hold a nut. There was probably another way that would have worked just as well, but we have found that aluminum rivnuts work well and are fairly easy to install for low-load applications. We have also used steel rivnuts for higher load applications, but they tend to be harder to install (and remove when they inevitably break) and not be as strong as a regular nut.

[RoboChair]

Originally Posted by GeeTwo

• 3/4" x 1/8" bar (Ace Hardware, looks like 6061, pictured above)
• 0.1" wall Vex 1"x1" tubing (I used a factory hole as a pilot)
• ~1/16" wall channel (sold as 1/2" plywood edging, also pictured)

If your ACE is selling 6061, good for them! But I would bet you $10 that it's 6063 and I HATE that stuff, super gummy and nowhere near as stiff.

Please don't buy hardware store aluminum. Please.

[frcguy]

Originally Posted by RoboChair

If your ACE is selling 6061, good for them! But I would bet you $10 that it's 6063 and I HATE that stuff, super gummy and nowhere near as stiff.

Please don't buy hardware store aluminum. Please.

I shamefully admit that at least 50% of the metal on our robot was bought from Orchard Supply.

Never again...

[GeeTwo]

Originally Posted by RoboChair

If your ACE is selling 6061, good for them! But I would bet you $10 that it's 6063 and I HATE that stuff, super gummy and nowhere near as stiff.

Please don't buy hardware store aluminum. Please.

This was all just scraps from my garage. For structural robot parts above the drive train, we use versa frame and 6061 channel (and a small amount of tubing) usually from Bayou Metals. When I do the more complete testing, I'll be sure to get some 6061 scraps from the recycle bin at the robot workshop.

Gummy? Would you please elaborate?

[FrankJ]

Originally Posted by cbale2000

Not to get too off-topic, but as someone who had never even heard of Rivnuts before seeing this thread, I'm curious... What are the actual benefits of using a Rivnut? Most of the application examples I've seen so far look like it would have been far simpler and faster to just use a regular bolt+locknut.

Lots of applications where you cannot get to the back side to use a nut and the material is too thin to thread.