Rev Nuts

[Michael Fling]

Riv nut- Rev nut. potatoe, potato. This may be a concern that doesn't need to be a concern? I have read of some concerns regarding potential galvanic corrosion when mating stainless steel and aluminum? So one answer might be using aluminum rivets or aluminum riv nuts with stainless screws. I would suppose the advantage would be that IF any corrosion occurred, the riv-nut could be removed and replaced? Does that make sense or is that over kill to a problem that doesn't exist? Has anyone used a hand tool for riv nut insertion or is an air gun necessary?

 

[Kyle]

Most stainless and Al matings are good, they are happy metals together for the most part.

Here is a galvanic referance chart for your own referance.
Galvanic series

 

[Seymour Snerd]

I would suppose the advantage would be that IF any corrosion occurred, the riv-nut could be removed and replaced? Does that make sense or is that over kill to a problem that doesn't exist? Has anyone used a hand tool for riv nut insertion or is an air gun necessary?

But let's not call the whole thing off....

You don't ever want to plan on removing a rivnut. They can be drilled out, but you never know what condition that leaves the hole in for re-use, and the size and quality of the hole has a significant effect on the integrity of the joint.

The concern in mating aluminum with stainless is usually with threaded fasteners, because they will gall on removal. Here, perhaps, "galling" would be a good thing since you don't ever want the rivnut to rotate. Some people add adhesive for the same reason although if installed correctly that should not be necessary. You don't usually use rivnuts in applications where high fastener torque is an issue. For the same reason, clean threads and anti-seize are a good idea, and carefully avoid cross-threading like the plague. A seized fastener in a rivnut can ruin your whole day.

The pliers-like hand-operated tool works fine up to and including 5mm. At about 6mm it takes a very strong hand, or both hands, to get the crimp to start, but once the crimp starts the rest of the crimp is easy. So if you're just getting started and are considering 6 mm or 1/4" and larger rivnuts, and can afford the extra $100 or so, I recommend getting the longer two-hand tool that looks like a pruner. Of course it requires much more vertical space above the work. I wish I had started with that years ago, because sometimes in trying to apply so much force to the smaller tool the rivnut gets cocked in the hole, and that's really bad especially in thin soft metal like on a GT40, and especially if you don't notice that it's cocked.

But in a pinch either or either will work.

 

[Jack]

ie: corrosion
a dab of epoxy just before installation, or a bit of anti-sieze. I prefer the epoxy and never had a corrosion issue.

 

[Randy V]

Hmmmm.... I've taken to putting a dab of epoxy on the outer shell of the Riv-Nut just prior to installing them (crimping in place) because I have had too many of them break where the nut and expanding rivet shell are joined. Once put in place, remove the installer tool and leave it alone for a day, then go back and gently try a bolt into the threads. Sometimes I have to go back and carefully chase the threads with a tap or thread chaser.
Once I'm installing the fastener, I always use just a little bit of antiseize compound to ensure that I will have the ability to take it back apart one day..

 

[Seymour Snerd]

...I have had too many of them break where the nut and expanding rivet shell are joined.

Interesting; I've not had that problem (yet). Trying to think of why that would happen (ignoring of course defective rivnuts) and all I can come up with is rivnut intended for thicker metal and thus being "over-folded"? Does this happen with just-installed rivnuts? I can imagine they might tend to corrode where they fold but that would take a while.

BTW, anyone ever gotten away with using thread locker on the fastener? I've never had the nerve to try it, although obviously one could experiment with scrap metal. And there is a "weak" (purple?) Loctite that might work..

<after a pause for some web searching>

It occurs to me that if you over-crimped a rivnut it would pull the nut part up into the rivet part in a way that would start to thin or cut into the folding part. See pic and imagine pulling with arbitrary force on the threads of the crimped part on the right.



Which raises the question of what is the ideal crimping force and how do you determine when you've applied it? Too little and the rivnut spins, too much and the rivnut fails. I bet the rivnut mfrs have a spec that says if the metal is x thick the compressed rivnut should be y long, or else a pounds-of-pull spec. But with hand tools I don't know how you would measure the latter. IAE not sure how we amateurs are supposed to deal with that, other than experimenting with scrap and sectioning a lot of rivnuts.... With hand installation there is a pretty clear point where everything "goes solid" and that's all I know how to do.

<pause for some more web searching I should have done in the first place>

See the attached document from Cardinal Components - Your source for Rivnut® engineered fasteners and installation tools. themselves.

View attachment Rivnut_Mechanical_Properties.pdf

It specifies an installation torque for each size. Which reminds me that the actual fastener itself can have the effect of "crimping" the riv nut as well. So (I'm thinking) the thing to do is crimp the rivnut short of the ideal force, and then when you install your fastener, just torque it as stated in the table. That, presumably, does not exceed the ideal crimp while also installing whatever it is you're mounting to the frame. Furthermore, the table says the figures are based on standards for torqueing grade 8 and class 5.5 fasteners, so why would you want to go higher than that? My thought is that if you think you need stronger fasteners and higher torque than that, maybe you shouldn't be using a rivnut.

BTW they make special "HRT Steel" rivnuts for use with class 12.9 hardware. (!).

 

[Michael Fling]

So clarify for me . Is it better to tap the frame and use a SS screw with anti-seize, or is it better to use a rivnut? If you don't ever plan on taking out the rivnut, I don't see the advantage of using one vs. just tapping and placing screw into frame???

 

[Seymour Snerd]

So clarify for me . Is it better to tap the frame and use a SS screw with anti-seize, or is it better to use a rivnut? If you don't ever plan on taking out the rivnut, I don't see the advantage of using one vs. just tapping and placing screw into frame???

Good question, and I don't have a good analytically-based answer. In my mind it depends on a couple issues:

1. If the frame material is either thin enough or soft enough, or both, the rivnut is stronger. To use an extreme example, with the soft 22 or 24 gauge steel used on the SPF GT40 it simply isn't practical to thread a hole, or for that matter, to use a self-tapping screw (IMO). Same for glass fiber and plastic. Usually your threaded holes are something like the same depth as the fastener diameter. So I'd be thinking about rivnuts wherever the frame thickness is less than that.
2. If you plan on removing and replacing the fastener frequently, the softer frame materials will wear out or have increased risk of damage from cross threading.
3. Pursuant to your original question about corrosion, rivnuts can buy you some compatibility; for example, if you want to use a stainless fastener and your frame is aluminum, putting in a steel rivnut will eliminate the stainless-aluminum galling problem.

 

[Jim T]

So clarify for me . Is it better to tap the frame and use a SS screw with anti-seize, or is it better to use a rivnut? If you don't ever plan on taking out the rivnut, I don't see the advantage of using one vs. just tapping and placing screw into frame???

Michael, I plan on threading all of my mounting points or through bolting on thinner material (when possible) and using anti-seize. You may not “PLAN” on ever removing them....but you know what they say about the best plans of mice & men! If can go wrong; it most likely will!


Just my 2 cents.
Jim

 

[Cam]

i was 3/4 of the way thru assembling and Alex said " you idiot, get a drill and tap bit. Just the 10/32 saved me 10 hours, thanks alex.
Ok, ive snapped 3 of them but still worth it. I've seen 0 problems with galling/seizing. i wish i had this tool in 2009. i also wish i bought 50 10-32 x 1/2" and 10-32 stainless x 1" button heads for anchoring

10-32 Fine Thread Combination Tap & Drill Bit | Fastenal

 

[Seymour Snerd]

i was 3/4 of the way thru assembling and Alex said " you idiot, get a drill and tap bit.

Now that is a brilliant tool.

 

[Jim T]

i was 3/4 of the way thru assembling and Alex said " you idiot, get a drill and tap bit. Just the 10/32 saved me 10 hours, thanks alex.
Ok, ive snapped 3 of them but still worth it. I've seen 0 problems with galling/seizing. i wish i had this tool in 2009. i also wish i bought 50 10-32 x 1/2" and 10-32 stainless x 1" button heads for anchoring

10-32 Fine Thread Combination Tap & Drill Bit | Fastenal

Cam and Alex, thanks to booth of you! I guess I'm old school, I never heard of this tool! I just ordered tow (2) bits.

Dam, I love this forum!!!!!!!!!!!!!!!:idea::thumbsup:

Jim

 

[Randy V]

Alan,

I was probably crimping too tight, but it seemed like if I didn't that the riv-nut would spin. Which is why I have taken to using a dab of epoxy.. I might have bought a load of bad aluminum riv-nuts too... The ones I have are really a shallow shoulder.

On tapping I was taught that you were fine if the material you were tapping was very close to or thicker than the fastener.. My RCR has a lot of holes that I have drilled and tapped.

 

[Randy V]

i was 3/4 of the way thru assembling and Alex said " you idiot, get a drill and tap bit. Just the 10/32 saved me 10 hours, thanks alex.
Ok, ive snapped 3 of them but still worth it. I've seen 0 problems with galling/seizing. i wish i had this tool in 2009. i also wish i bought 50 10-32 x 1/2" and 10-32 stainless x 1" button heads for anchoring

10-32 Fine Thread Combination Tap & Drill Bit | Fastenal

I will be ordering some of these... Cool!!!

 

[Seymour Snerd]

I might have bought a load of bad aluminum riv-nuts too... The ones I have are really a shallow shoulder..

Oh, well, I've never used aluminum ones, just steel, so that explains why I haven't had the problem.

On the other subject (drill-taps, aka draps), Greenlee makes sets of them that are on ebay for less than $30 (for the set!). I just bought one each metric and inch.

Another good thing to use with a drap would be this: http://www.v-drillguide.com/index.html since you don't want them going in crooked either.

Guess we should change the thread title to "attaching things to other things."

 

[mark b.]

i have used a boat load of the steel rivnuts, they are zinc chromate coated so corrosion shouldn't be a problem. i use the air guns, one for 10-24/32 and 1/4", and another gun for the larger stuff. i have used them in aluminum, steel and fiberglass. using an 80#psi air compressor i pull the nuts as far as the gun will take them, back off and hit them again. the only problems i can remember is not pulling them far enough. when you do use them, you can pull them pretty tight and feel the nut pulling up again, this is the time to stop. the only time they fail is if they are not pulled tight enough or the hole is too big. if the threads get messed up, just drill them out and put in another. when i initially started using them i used 10-32, then switched to 10-24, i would recommend not mixing threads and stay with the coarse ones. here is where i get my supplies, the guns were initially $200, but they have gone up considerably, but imo if you are going to use a few, buy a gun and a box of fasteners, when you are done sell the gun, money and time ahead.

https://www.lefthanderchassis.com/v2a/products.asp?idcategory=1145

wow, they keep going up in price, when i bought mine 5 yrs ago they were $200, last year they were $280, now i see they are $320! one of mine even has 'guard shack' stenciled on it, makes me wonder if and how it was used.

 

[Scott Davis]

Can somebody explain whats the difference between rivet-nuts, ribbed-nuts, poly-nuts, and thread-serts?

 

[Graeme Stebbing]

hi Scott I posted this back in march 14 good info could be useful to those who missed it
LocostUSA.com &bull; View topic - Rivets and Rivnuts 101