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Back Riveting Question

dwollen89

Well Known Member
I've been charging along on my tail kit. I hope to be done in the next couple weeks. I'm currently back riveting stiffeners into the elevator skins. I'm noticing that some of the rivets, probably about half, seem to very slightly clinch over to one side. I've tried about everything possible to change that, including different air pressures, making extra sure the rivet gun is square to the work, etc, but it seems to keep happening. Is this normal? I feel like the rudder went much better, but those rivets were shorter. I asked my tech advisor and he said to make sure the rivet was centered in the back rivet set. I tried that and made extra sure, but same result. I think I'm pretty good at bucking rivets, so I bucked a couple rows and noticed that some of those rivets did it too. Any thoughts? Is this normal? Am I being too critical? Here's a picture.

https://photos.app.goo.gl/9BsMJxooQmzULXxXA
 
It could be the collar on your backrivet set is hitting the radius of the stiffener and slightly knocking you off 90deg. I ground a slight chamfer into one side of the collar on my set for this reason.
 
Thanks for the reply. That's a good point and I'll give it a try. I'm also wondering if I need a different back rivet set. I have the one from Cleaveland and the face has a slight concave into the center. I'm going to borrow a different brand set from a friend and try that.
 
At some point I figured out that the slight clinching is caused by the tool moving while pounding the rivet. Do what you can to keep the tool from moving while riveting: Hold the collar steady with 1 hand, gently squeeze the trigger rather than yanking it... Others also swear by backriveting on a rock-hard surface rather than a less-than-solid table. The floor even. I haven't tried since seeing that bit advice.
 
It could be the collar on your backrivet set is hitting the radius of the stiffener and slightly knocking you off 90deg. I ground a slight chamfer into one side of the collar on my set for this reason.

This^^^ Grind a flat spot on the plastic collar to ride on the upright of the stiffener.
 
Thanks for the reply. That's a good point and I'll give it a try. I'm also wondering if I need a different back rivet set. I have the one from Cleaveland and the face has a slight concave into the center. I'm going to borrow a different brand set from a friend and try that.

absolutely not....I have the cleaveland one and thats how they are made...actually helps to keep it centered. grind the flat on the plastic...that will bear against the radius on the stiffener and throw you off.....hold the plastic end with your fingers...squeeze the trigger to just get the gun started and then give it a burst....practice on a few on a non jeopardy setup you make first
 
I had exactly the same issue when I started back riveting my rudder. I was lucky to have an extra skin that arrived damaged and was replaced when I first got my kit, so I made some extra stiffeners and ran lots of test before going back to the real thing.

I still can't tell you for certain what was causing the problem, but in the end it seemed to be a matter of my technique. It seemed that a slight lean or movement would cause a less than perfect rivet. It was frustrating because, even when I felt that I was steady as a rock, it would happen.

In the end, there were two things that made a major difference for me. First, my pressure was way too high. I tried to set the pressure around 25, but my regulator seemed happier operating around 30-35. This pressure was still low enough that I had much better control when I pulled the trigger. Second, I changed back rivet sets. I started with the smaller diameter set with black collar from cleveland. It seems like that would have been the better option because of the close clearance to the inside radius of the stiffener. However, when I started using the larger diameter set from aircraft spruce, I had more control and more consistent results. I think the wider and more robust collar, made it easier for me to stabilize perpendicular to the rivet and to hold still as I fired the gun.

All said, I was shocked that this gave me so much difficulty, since I felt that I had gotten quite confident at bucking rivets. On the actually rudder, it was still challenging for me. The consistency wasn't perfect, and for the first time in the project I accepted rivets that were set within tolerance, but less than perfect. I drilled out a total of 3 and reset. Those all went well.

It's amazing how humbling every part of this project can be. Wish you the best, let us know how it goes!
 
Has anyone experienced corrosion where the aluminum and the back riveting plate come into contact? I had this happened in a few spots. It was an outline of the plate on my skin.
 
I'm convinced that it's the Cleveland back rivet set. I don't know what else it could be. I've tried everything, including every suggestion above, and the rivets just will not consistently set straight. I'm going to try a different rivet set and see what happens.

I'll update with the results.
 
collar

Try removing the spring loaded collar from the back riveting set, there should be a roll pin that can be knocked out. You will need to keep the set centred over the rivet by pressing down with a finger either side of the business end.
Something additional to try is a piece of riveting tape or scotch magic tape over the factory head of the rivet.
 
Back riveting

I have observed the pressure needs to be significantly lower than bucking. I run 20 psi.
A gun regulator really helps keep pressure stable.
I use a RTI 1/4" Mini. Awesome regulator. Never moves.
Steel plate needs to be really stable.
 
I stopped at a buddy's house and picked up his back rivet set which is from Planetools. The first row of rivets that I did set perfect! I honestly think it's the concave face on the Cleveland rivet set. I really like Cleavland tools, but that back rivet set is going in the garbage...

Thanks everyone for the tips and help! What a great bunch of people here!
 
RTI 1/4" Mini

I have observed the pressure needs to be significantly lower than bucking. I run 20 psi.
A gun regulator really helps keep pressure stable.
I use a RTI 1/4" Mini. Awesome regulator. Never moves.
Steel plate needs to be really stable.

Would you share a pic? Is this a gun mounted regulator or mounted on wall with dryer?
 
HF pigtail

Would you share a pic? Is this a gun mounted regulator or mounted on wall with dryer?

Actually, it's a Harbor Fright pigtail. My air hose has a three port manifold at the end. I keep two of these plugged in. One for high pressure tools like the squeezer and drill. The one with the RTI regulator is for low pressure tools.
https://www.harborfreight.com/1-4-quarter-inch-x-5-ft-swivel-whip-hose-98944.html
RTI Mini 1/4" regulator is at one end.
https://a.co/d/0evEljN
Quick connects on either end allow me to use it on any tool.
It sets quickly and never changes.

I do have one on my paint gun. Painting is more consistent if the pressure is consistent. Long hoses at low pressure used for HVLP can fluctuate.
20220820_082044.jpg
 
See Thread "double offset rivet set"

In post #2 of this thread (3-4-21) I show a couple of double offset back rivet sets that I made. The explanation of why they work is there. I don't know why someone doesn't offer these as an alternative to the bigger, clunky, spring loaded ones - but they don't. The beauty of this design is that it lends itself to the DIY/MYO option.

Shown below are a couple of straight versions of the same idea. As long as the end is counterbored as shown, you can make about any length, diameter or shape that you need in very short order.

OBTW - Can't remember whether I mentioned this in the previous post, but the angle handled wrench is used to "press" together the sections of skin being riveted, if needed, i.e. stiffeners to skin. This provides the same function as the spring loaded "collar", but you control the force applied - instead of taking whatever the spring rate is on the collar mount. You can be way more aggressive on the pressure applied - to get better accommodation between sections.

YMMV - but these work.

HFS
 

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