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

2104 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


Notes:
  • 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.

Results:
- 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).

Observations:
  • 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.

Conclusions:
- 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: https://faroutride.com/threaded-inserts/
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!

Conclusion:
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!
Cheers,
Antoine
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This subject always gets lots of posts with very different opinions. Kind of like discussing religions.

I have built two conversions. Tried rivnuts in beginning on first van but determined that the $30 McMaster-Carr tool made it very difficult to put in a rivnut in a hole in the roof rib. Three hands required. Two on the wrenches and a third to hold the rivnut up into the hole. Quickly changed to Plusnuts. Type of tool makes a difference. The advantage of the McMaster-Carr tool is its size because it is small enough to be used in places a large tool would not fit.

Another advantage of a Plusnut is the hole diameter is not critical and they work in hex holes. The Plusnut feet extend much further than a Rivnut bulge.

A disadvantage of the Plusnut is they are longer. Several places in the Transit have holes that the Plusnut cannot be fully installed because end of Plusnut hits steel behind the hole before flange seats against wall hole. I found that after Plusnut is partially installed you can start the install process to shorten the Plusnut and when it is shorter it can be pushed the rest of the way into the hole so install can be completed.

Had no difficulty installing the Plusnuts with the inexpensive McMaster-Carr tool. Used existing holes for 1/4-20NC Plusnuts. Light tap with hammer gets the Plusnut into the holes. Used plated mild steel Plusnuts with SS bolts. Did not use thread lube. Did use tread lube where I had a SS bolt and elastic stop nut in 80/20 structure. Installed without a torque wrench by "feel".

After I had completed the Plusnuts without difficulty someone here or on the Sprinter site mentioned that there is a flange under the head of the Plusnut that prevents it from seating against the hole steel. Never noticed the flange when installing them. The suggestion was to put a star lock washer on the Plusnut before installing the Plusnut. Excellent advice. I would use the lock washers if I ever need to install Plusnuts again. Makes sense when you look at the Plusnut.

I did have to use a tap to clean up the threads on a couple of Plusnuts. Probably caused by not keeping the tool perpendicular to the wall hole. Never had a spinner.
 

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Two hands, I used a cordless impact wrench and a wrench on the McMaster-Car tool, The Rivnut/Plusnut screws onto the mandrel of the tool so there is no need to hold it.
Correct. That would work. I do not own an impact wrench. When using the $30 tool and two box wrenches nothing holds the Rivnut and tool in the hole before it is expanded. A pre-bulbed Plusnut does not fall out of the overhead hole like a Rivnut. I guess you could determine the correct torque setting on the impact wrench instead of relying on "feel" for the two box wrench method.

The Plusnut was a better choice for me because I have a low skill level.
 

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Yeah ok, I was pushing on the impact wrench and that held the Rivnut in the hole
When the inner nut of the mcmaster tool comes completely unscrewed that sets the torque on the rivnut/plusnut, Giving you perfect torque every time. It does not matter, Impact or wrench, That is how the mcmaster tool works.
Thanks for the instruction. Did not know how the tool works. I just tightened the tool by feel. Had no difficulties installing the Plusnuts. No issues installing Plusnuts in the two builds. Find it interesting that there is so much discussion about this subject.
 
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