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Plus nuts (again). Ugh.

30K views 86 replies 26 participants last post by  BobCollins  
#1 ·
I've read the prior threads on plus nuts, and I've tried to be careful but I'm running into problems. Using the Astro tool and some 1/4-20 plus nuts from Amazon.

We tried the tool and nuts on a spare piece of van sheet metal. It felt like we had a decent feel for the 'correct' amount of squeeze to apply, but it's not like there's a clear "exactly right" amount. Some of our nuts have begun to spin, and on at least a couple we are unable to get the tool back in to tighten them down. We don't have access to apply glue, since this is the ceiling beams we're working on. It also seems that almost all of nuts have slightly shonky threads once installed -- they seem to need me to put a normal bolt into them after installation to somehow "sort out" the threads.
  • What options do I have on a spinner where I can't glue or grab it? I'm trying to dremel the sides down so I could hold it still with pliers and get the tool in for another crunch.
  • If I'm crushing the threads on install, am I doing it wrong? Is it normal for the threads on a plus nut to be, basically, a bit crappy?
  • For some of the nuts I might be able to slip a washer behind them -- worth doing to improve success rate where possible?
The "threads aren't quite perfect" thing is a real bummer because trying to get the bolt into slightly 'off' threads means it's even more likely to spin. I'm feeling sad, please save me from self-tapping screws...
 
#2 ·
I feel your pain. On the first ordered batch of plusnuts, (Astro 1450) I was applying to much force. This seemed to result in the thread portion kicking to one side and out of alignment. That lead to difficulty unthreading the tool. I salvaged them by carefully retapping the threads. The second batch from the same supplier required much more force to seat correctly. I under set a few and had to reset them. It was very easy to reinsert the tool if they were not fully set.
 
#3 ·
If the threaded mandrel of the install tool does not thread to the end of the insert, you might be distorting the thread a little if you apply a lot of force, use a Tap a to chase the Threads if needed. A washer (Spacer) is the best thing to eliminate spinners, I have used split ring lock washers and plain washers, some people have used Tooth Lock Washers which is what I will use going forward, the thickness is .032-.040 which is enough to do the Job, the Split Ring Washers work but are thick .095, the plain washers also work but the OD. Diameter is large. Do a search on this site, it has been talked ad nauseam, the easiest solution is to add a little spacer and Bob's your uncle.

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#4 ·
use a Tap a to chase the Threads if needed
To clarify: another thread indicated there's a difference between a tap (cut new threads) and a chaser (clean up existing threads). I can't find a chaser in stock anywhere, but I can find plenty of taps. Is it ok to use a tap to clean up the threads?

I'm re-reading your thread about the washers, and I thank you for the info, I'm making a specific thread for the problems I'm having because I thought I'd read all the existing material and clearly still am screwing something up. I'll get some split washers and practice on my sheet metal, but that doesn't help me with the existing spinners :-(
 
#5 ·
I'm feeling sad, please save me from self-tapping screws...
It would not be the end of the world. Seven years ago when I was building, I had never heard of rivnuts or plusnuts. Self-tapping screws have held my ceiling up just fine. I now have three rivnuts in fairly recent addition, but I’ve never seen a plusnut.
 
#8 ·
And again every time this problem pops up it is with people using that style plus nut, use the other style.
I believe I'm using the style mentioned by Far Out Ride, but I'm not actually clear on the two styles. What's the difference? (I understand plusnut vs rivnut, didn't realize there were different flavors of plusnut).
 
#16 ·
I have installed close to 500 of the second style, Steel "twist resistant" Rivet nuts. Pretty much describes what they do right there in the name. Not sure what anyone would use something for plastic? And I used the Mcmaster sold threaded tool and a dewalt impact to install all 500 of those. I had maybe 3 screw up, all my fault.
 
#13 ·
The gist of it, is to use a spacer, a thin one .032 -.040 is plenty thick. internal or external Tooth lock washers seems made for the job. The sheet metal in some places is .028 thick (with paint) which is very close to the bottom of the Grip range 0.027" to 0.165" and 0.020" to 0.280" of these Threaded inserts, While the Split Ring lock washer works fine, its .095" thickness adds unnecessary stack height. I know many people have installed these Rivnuts without spacers and had No problems. For the people who are all thumbs just use a thin spacer.
 
#14 ·
We tried a couple plusnuts on our last van and didn't approve. Seems like the rivnuts grab better if done right; so this van is all rivnuts.

Found that the Astro tool worked best when we got rid of the back knob for threading them into/out-of the rivnuts and clamped on a small vice-grip pliers to control threading the mandrel into the nuts. We also run a thread tap (female tap - whatever that's called - a "die" maybe?) over the mandrel to keep the threads clean-ish since that seemed to be a thing. And ran a tap through any nuts if we trashed them a bit (which definitely happened). (Using this tap and die set.) We settled into running the mandrel and/or nuts through "cleaning the threads" pretty frequently.

We've only had a couple of them go bad (out of a couple hundred - after figuring it out on the first dozen or so). We've been able to clamp the front ring with needle-nose-vice-grips or Vampliers then re-thread the mandrel. Worst-case, we've threaded the mandrel /outside/ of the tool, then assembled it with the mandrel in the questionable nut. Either way, once the mandrel was re-threaded, we were able to create enough pressure to lock the rivnuts back in - none had to be removed. Thought we were going to have to drill out the outer ring a couple times; but always got it to lock back in.

We did realize that there's a Goldilocks point of pressure (at least on rivnuts). Not "as hard as possible" but more "pretty darn tight" seemed best; the super-super-tight seemed to trash the threads more frequently.

Might want to at least test some rivnuts instead. We ran Astro's rivnuts. Tried the Glarks; they were okay but not as good.


Funny how few photos we have of doing rivnuts. I took a few when we first did the first ones in the Sprinter - to mount the bed rails to the side of the van - because it was such a novel premise to us at the time. This photo is before we got better at keeping the mandrel straight and before we started using the vice-grips to thread the mandrel into the rivnuts. And you can see that we're off-angle just a bit. Turns out that was a bigger problem than clamping them super hard.

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#23 ·
I installed about 200 in the van and didn't have a single problem with one spinning. I used the tool from mcmaster-carr and a Milwaukee electric ratchet to tighten it. I would let the ratchet tighten it until it stopped and then sometimes crank it an extra 1/4 turn or so. Really went by feel. I didn't need any washers anywhere in the van. I used existing holes MOST of the time.

Here are the tools i used:
McMaster-Carr

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#25 ·
I installed about 200 in the van and didn't have a single problem with one spinning. I used the tool from mcmaster-carr and a Milwaukee electric ratchet to tighten it. I would let the ratchet tighten it until it stopped and then sometimes crank it an extra 1/4 turn or so. Really went by feel. I didn't need any washers anywhere in the van. I used existing holes MOST of the time.

Here are the tools i used:
McMaster-Carr
On that McMaster-Carr page, there are many installation tools. Can you narrow it down a bit? Which one(s) led to your success? Thanks.
 
#29 ·
I've installed a countless number of Plusnuts in my van without issues and without an official tool; just used a couple of wrenches. Simple, quick and useful. Have a short video that shows it. Hope that helps.
Van Williams
 
#30 ·
I used the same method of using 2 wrenches and after a couple determined 10 or 11 turns was the best. So then I used a socket marked to make it easy to count the turns and a battery powered impact driver. Of over 40 only one spinned and it was due to a bad angle when installed. I did use a star washer right next to the plus nut then a washer, wrench, washer, bolt.
 
#31 ·
Something that I'm still confused by is how much extra work people insist on doing just to use 1/4-20 rivnuts. Like . . . the van is metric. The already tapped mounting points in the wall are metric. The holes in the wall are already perfectly sized for M6 rivnuts/plusnuts. Every single other bolt/hole/fastener on the entire van is metric.

And yet people insist on going through a bunch of extra work to drill, deburr, corrosion protect, clean metal shavings out of the walls, just to enlarge the holes a little bit so they can use SAE bolts?
 
#32 ·
And yet people insist on going through a bunch of extra work to drill, deburr, corrosion protect, clean metal shavings out of the walls, just to enlarge the holes a little bit so they can use SAE bolts?
I dunno what other people are doing, but the 1/4-20 plus nuts that I got just drop into the existing holes. If I had needed to enlarge the holes I would have thought twice.

To bring this thread to something of a conclusion, I think I've figured out why my success rate has been so low. I'm trying to do something difficult, which is using plus nuts in the roof to apply a nice bend to 1/2" furring strips. The force needed to create the bend makes it very difficult to thread the bolts into the plusnuts exactly right, and the net effect is the threads are much more likely to lock up and create spinners. I think if I used plusnuts in the walls to bolt simple panels to, they'd be fine. It's the force I'm using to create a bend in the furring strip that is causing most of my issue.

I now like the nice curve to these furring strips so I'm figuring out a way to keep that while not buggering all of the plus nuts into spinners. Once these darned things are up they're never coming down. I'll post photos once I achieve victory.
🤞
 
#50 ·
Just when I thought I was out, they pull me back in!

(the M6 - 1 Rivnuts have the same external dimensions the tapped hole is the only difference)
Here are the two different 1/4-20 Rivnuts:
pre-bulbed plus nuts: specified hole size .386 - .391
straight body nuts: specified hole size .347 - .352

If you are concerned about the existing holes size dia. .368 in the van being to big for the straight body nuts don't worry the straight body nuts will grip just fine. this style of insert doesn't grip by expanding the shank like most of the other style of inserts that are used, most threaded inserts, pem nuts etc. call for a hole dia. with a tolerance of -.000 +.003 with this style if insert it is not necessary to maintain the hole tolerance specified by the manufacture for installation. If you use the specified hole sizes the plus nut might be better centered in the hole, but for our use, having the plus nut .008 off center of the hole is going to make no difference, it's the petals that fold out to .78 dia. that clamp the insert in place, do a few test holes and it will all become clear.

They are the same except the pre-bulbed nuts start with a body dia. of .334 dia. then are bulbed out to dia. .380 then they taper back down to dia. .344 until the small step under the head which is approx. .040 high x .390 dia.

The straight body nuts start with the same body dia. of .334 dia. then do bulb out slightly to dia. .344 this dia. continues all the way to the head, and there is No step under the head.

I found no noticeable difference in the install torque between the two using a manual tool.(shown in picture) Like I said before, I would use the straight body nuts with a internal tooth lock washer (for the increase in thickness which aids clamping, reduces the chance of spinners) some of the sheet metal in the van measures .028 thick with paint, the Grip range is .020 - .280 on these inserts, if you are going thru thicker metal or doubled up sheet metal there is no need for the internal tooth lock washer.(although wouldn't hurt) The pre-bulbed plus nuts also work fine, you have to tap them in with a hammer (orton). the small step under the head may or may not help or hurt, The small step is there to help center the insert in the recommended hole dia. of .386 - .391

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#51 ·
Just when I thought I was out, they pull me back in!

(the M6 - 1 Rivnuts have the same external dimensions the tapped hole is the only difference)
Here are the two different 1/4-20 Rivnuts:
pre-bulbed plus nuts: specified hole size .386 - .391
straight body nuts: specified hole size .347 - .352
I am planning tests tomorrow with regular rivet nuts (not plusnuts). I am using 1/4-20 rivet nuts with an 8.9mm (0.350") body diameter. They are generally specified to be used in either a 9mm (0.354") or a 3/8" (0.375") hole.

I don't currently have any 9mm drill bits, so I will try 23/64" (0.359"), 3/8" (0.375") and test how much torque I can apply before the rivet nut slips (torques out). To be application specific, I plan to use the metal that I removed from the roof (0.032") when I installed my ceiling fan.

I will also try drilling with a 11/32" (0.344") bit and ream the hole as necessary until the rivet nut fits. I will then repeat the test.

I would be interested in the results of a similar test done with various plusnuts and hole sizes.

A request: I understand where it comes from, but it would be clearer in this discussion if you didn't intermix the terms rivnut (generically rivet nut) and plusnut. They really are different animals.
 
#54 ·
I am a machinist by trade, I have used the Rivit nuts a few times, controlling the hole size for a close fit they seem to work fine, The first time I used Plusnuts is on my van,I read about them on Ortons tale of the Van. I am very satisfied with the performance of the Plusnuts, the only downside I see with Plusnuts is they are quite a bit larger on the backside which may cause interference issues, and it looks like they cost a little more. but for the number of Plusnuts I will be using on the van that is a non issue. Either style of insert should work fine.
 
#55 ·
Here is mention of using the Plusnuts on Sprinter Van conversions.

"Sprinter or work van enthusiasts prefer the PLUSNUT® as their go-to internally threaded slotted body rivet nut fastener solution."

 
#71 · (Edited)
I'm not sure how you have come to this conclusion? You can under or over torque the McMaster tool. I used a torque wrench with it, and found that there is a sweet spot (around 20-22 ft-lbs) ] just before the plusnuts start to deform that prevents any spinning. Any less torque, and you can possibly get a spinner. Any more, and the plusnut threads distort.

That being said, it's still super easy to use and I highly recommend it. I don't know why everyone makes this a lot harder than it needs to be. The only way to get consistent results is to use a tool like the McMaster, and a torque wrench. Just like any other important bolt in the van, you use a torque wrench to ensure proper installation, no "go til it feels right." Air tools possibly can provide the proper/consistent torque needed assuming consistent/proper psi
 
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