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CrossNuts vs RivetNuts (and other hacks): An Experimentation on Spinout Resistance

2084 Views 30 Replies 19 Participants Last post by  Bajabound
I used cross nuts exclusively for my first build and had great success with them. But lurking on the forum, I noticed many people are struggling with "spinners". I spent HOURS on forums trying to find what's the latest consensus on threaded inserts, but no luck. It's still a endless debate. It's hard to thrust someone's opinion when there is no data to back up their claim...

So I went ahead and attempted to QUANTIFY spinout resistance torque of CrossNuts and RivetNuts. In addition, I tested a few "hacks" often mentioned in forums: regular washer, split lock washer, tooth lock washer, CA glue, Red LocTite, and J-B Weld:

Measuring Spinout Resistance

Spinout Torque Results

  • I didn't use "fixed material" between the insert and the bolt (which creates friction on the insert's head and increases spinout torque). That intentional, my goal wasn't to quantity the "real-world" spinout torque. I just wanted to compare different inserts/hardware spinout resistance, so I took the "fixed-material" out of the equation (which was one more variable).
  • My test sheet is 0.032" thick and holes are 0.364" to simulate standard holes on the Transit.
  • The spinout torque was recorded with a digital torque adapter.

- Rivet Nuts (alone) and Cross Nuts (with tooth lock washer) gave the best results. In fact, the spinout torque was beyond the recommended torque for a 1/4 bolt (grade 5) and I was able to shear a few bolts (or damage the crossnut/rivnut).

  • CrossNuts (without hardware) spinout torque varies a lot, and it's hard to obtain repeatable results.
  • The tooth lock washer increases the spinout torque a lot, and also helps installing the crossnut straight and flush with the mating surface. Win-win.
  • Rivet Nuts installation is very predictable and repeatable.

- I'll probably prioritize Rivet Nuts on my next build, but still keep a few Cross Nuts handy for the oversized or oddly shaped holes (hex, square).

Learn More:
This is a short version of what you'll find here:
In the link above I also got a 360° virtual tour showing ALL sizes/locations of threaded inserts in the Transit cargo area. I'm pretty proud of that and it should be very handy!

It might not be a huge revelation, but at least I've got data to back up my decision for my upcoming build! :)

OK I'm done here, up to the next project!
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Discussion Starter · #4 ·
Great study. Thanks for posting. Also for documenting all of the hole sizes in the Transit.
Do you happen to have the spec. or a link for the toothed washer that you used?
Do you have any insight/opinion on the difference in pull out strength of cross nuts vs rivnuts.
For M6 or 1/4 crossnuts/rivnuts: 3/8 Tooth lock washer.
1,215lbs for the crossnuts, 480lbs for the rivnuts. In my opinion rivet nuts have sufficient pull-out strength. Unless, of course, they're installed in oversized holes (e.g. M6 rivet nuts are spec'd for 9mm hole and seems to work well up to ~10mm hole. I tried 11mm and the hole was definitely too large).

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