Remember to use washers and not over tighten

[Peter Matteson]

Originally Posted by Mr V

Using the knurled version like I linked to is preferred over the smooth version. The other big key is to make sure they are installed properly. Having a good tool is part of that equation, so you can ensure the proper compression is achieved, as is making sure that the hole is the correct size. If it slides into the hole easily the hole is too big.

Here is a good tool from McMaster. I'm not finding the one we use, if I do I'll update.

I'm with Mr V on this. I've never had a properly set rivnut fail in Al. The only issues I can thiink of are when you try to set it in a material with a higher Rockwell hardness which prvents the knurls or splines from digging in to the parent material.

We have had issues when people who haven't used them before don't compress the nut all the way however, which I was reminded of last night when I realized the only person on the team other than me who installed our rivnuts for the last four years graduated last year.

[FrankJ]

The big thing I do not like about rivnuts is when the do fail, the corrective action can be time consuming. I know in a perfect world they will not fail, but the heat of a six week build session & multiple matches in tournament tend to cancel out the perfect world scenario. They are useful in their place & are better than tapping thin gauge Al. I second the idea of using the installation tool to set them. It has hardened face to get a consistent set.

We put PVC spacing in between anywhere where we will be tightening a lot. It's light, durable, and a great option for any team who is without rivets.

Note to self: Get some rivets.

[FrankJ]

Last year we put spacers in the AndyMark wheels to prevent binding the bearings by over tightening the axles. I have a mechanum hub that is deformed from over tightening. Seems like about the time people are trained to be aware of the issue, they graduate. ;(

[JesseK]

We only put the bolt through 1 wall of the tubing. We use round socket or phillips bolts, and bore a larger hole with a stepper bit (not sure of its official name) on the opposite side for access. We have a magnet in case the bolt drops. We did this on our drive train last year, and on a pretty high sheer-stress piece in prototyping this year. We haven't had a single problem yet, and the drive trains had (have again this year) only 1/16" wall tubing. The key is torsional support.

It also saves us some weight (maybe 1lb) overall on the bot since the bolts are all 1" shorter.

[Mr V]

Originally Posted by FrankJ

The big thing I do not like about rivnuts is when the do fail, the corrective action can be time consuming. I know in a perfect world they will not fail, but the heat of a six week build session & multiple matches in tournament tend to cancel out the perfect world scenario. They are useful in their place & are better than tapping thin gauge Al. I second the idea of using the installation tool to set them. It has hardened face to get a consistent set.

Yes if they start spinning in the material the corrective action could cause problems particularly when using something harder than a grade 5 bolt. The knurled ones are less likely to spin than the smooth sided ones, which I would not recommend for anything that will be disassembled and reassembled multiple times. The other key it to not over tighten the bolts going into them and of course not to cross thread said bolts.