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Riveting separation

Golf Echo

Active Member
Greetings,

Hopefully I don't win a prize for dumbest first post ever, but here goes...

I've received and inventoried my empennage kit for what will someday become an RV-7. I've pondered my choices for engines and avionics, but today, my question is a little more rudimentary... :eek:

practice%2520separation.jpg


In riveting the reinforcement plates and ribs to the spar (of the practice kit) I'm getting some deformation and separation of the rib flange (see photo). I'm using the Cleaveland pneumatic squeezer to set the rivets. Is this simply an issue of inadequate clamping? I tried putting a cleco clamp near to the rivet being set, but it didn't seem to help. I'm going to drill them out and re-rivet for practice, but I figured somebody might have seen this before. Any thoughts?

Thanks in advance for the help. This site has already been an enormous resource for me.
 
Tweaking that flange to fit as flat as possible will help. Even so, sometimes you get spreading like that. Lots of ways to deal with it, but try a tiny pair of needle nose vise grips (taped jaws) on each side of the hole. Tricks like that start coming natural after awhile.
 
My suggestion is

that the parts should be "nested" together better before riveting. Try squeezing the whole assembly with your dimple dies before riveting. I did this a lot resulting in much better fit and riveting results...:)
 
Rubber grommet

Put a rubber grommet over the tail before you squeeze. As the squeezer starts to "squeeze" the rubber will compress all the parts together and then the shop head will form. Works great. You can get a bunch of them at HF for cheep. Hopefully I explained that correctly.
 
Putting the rivet in the other direction may help in some instances. Although not always possible. Love the rubber grommet idea.
 
Puckered.

That happens when the set rivet swells the hole and puckers the flange of a thin piece. Set less or reverse the rivit direction. Leave that one alone, you can only make an acceptable joint worse at this piont. the metal has been streched and won't pound compleatly flat.
 
You oversqueezed a bit too.

That happens when the set rivet swells the hole and puckers the flange of a thin piece. Set less or reverse the rivit direction. Leave that one alone, you can only make an acceptable joint worse at this piont. the metal has been streched and won't pound compleatly flat.

Seems like over-setting a bit might be the culprit.

The strange thing is that the shop heads of both those rivets fit inside the rivet gauge. Because of that, I didn't think I was over-setting.
 
Putting the rivet in the other direction may help in some instances. Although not always possible. Love the rubber grommet idea.

In the Van's documentation, they suggest putting the factory head on the side of the thinnest piece. Makes sense to me. But, in looking at some other's photos, the factory head was on the leading side of the spar, so I did it that way. Not really sure why I didn't keep the factory head with the thin material...
 
This is precisely what side-grip clamps (used with cleco pliers) are used for. It will solve this problem 99% of the time.
 
I don't know about others, but I eventually abandoned pneumatic squeezing for hand rivet setting on all but the heaviest rivets...too hard to control. For small and separate parts like that, most rivets can be set on a dimpler very nicely, especially the bigger DRDT-2 . It's a bit expensive, but it's really versatile (good control with both dimpling and rivetting---just change the inserts) and is a dream to use. I don't have one (I built my airplane with a much less "handy" classic hammer style Avery "C" dimpler, but a friend on the airport has a DRDT-2, so nowadays for follow-on projects, I always cruise down to his hangar and put his to use. If I built again, a DRDT-2 and a full set of dies would be the first tools I add to my inventory.

Lee...
 
Put a rubber grommet over the tail before you squeeze.

The best thing I found was a soft thin piece of wood like from a paint stir stick. The grommets worked if I could keep them in place. My first choice was always to bend it better so it nested flush or hold it with side grip clecos or even carefully hold it while squeezing. The piece of wood was easy to hold in place with a piece of tape or even with one hand while pneumatic squeezing with the other hand. It has to be soft, though. A popsicle stick is too hard. Soft enough to indent the rivet tail while pulling the pieces together and crush for the last of the squeeze.
 
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Welcome to VAF!

Graham,
welcome.gif
to VAF.

Good to have you aboard.

The advice given you above is correct, sounds like you just need to practice.

One thing I had trouble with using a pneumatic squeezer is that I needed to put more pressure against the rivet head before I hit the trigger, it is pretty easy to not have the rivet seated in the part, and yet squeeze it anyway.
 
Graham,
welcome.gif
to VAF.

Good to have you aboard.

The advice given you above is correct, sounds like you just need to practice.

One thing I had trouble with using a pneumatic squeezer is that I needed to put more pressure against the rivet head before I hit the trigger, it is pretty easy to not have the rivet seated in the part, and yet squeeze it anyway.

Thanks, Mike. I think for those rivets, I had to use the cupped set in the ram and the flat set in the yoke. It was probably even harder to keep good pressure on the factory head because of this.

More practice it is... glad I ordered the practice kit with my empennage.
 
...The strange thing is that the shop heads of both those rivets fit inside the rivet gauge. Because of that, I didn't think I was over-setting.

When I first started my empennage, I misunderstood how to use the rivet gauge. I thought the rivet shop head should "just fit" inside the hole in the rivet gauge, so my first few rivets were underset. Then I found out the shop heads should "not quite fit" in the gauge hole, so I had to go back and re-squeeze a few rivets.
 
Been there - done that....

Thanks, Mike. I think for those rivets, I had to use the cupped set in the ram and the flat set in the yoke. It was probably even harder to keep good pressure on the factory head because of this.

More practice it is... glad I ordered the practice kit with my empennage.

Happened to me on the final parts of the HS assembly for the end ribs rear flange-to-rear spar attachments. One side set correctly but the other had the same problem your pic is showing. So I drilled out the bad rivets carefully using an AN470 rivet removal tool from Cleaveland Tools, and reversed the direction of the rivet to help pull the parts together. The result was one side of my HS has the manufactured heads going one direction, and the other side has them facing the other direction. I did not really care about the visual symmetry aspect of it - as long as the parts were properly attached that was fine with me.

About the location of the rivet sets - you are right on the mark about noticing which end of the "beast" you have to put them on. When at all possible I try to place the sets in such a way that I wll be able to pull or push parts closer together with solid pressure against the manufacured head of the rivet (also mentioned previously by someone), meaning you want to postion that rivet set on the yoke side (non-moving side) of the squeezer and not on the ram (moving) side. The thing that makes this difficult is that you have to make certain you keep the squeezer and rivet sets centered on the rivet so that you don't miss all or part of the shop head with the ram when it makes contact. And sometimes you just don't have a choice but to configure the rivet sets in a less than optimal way due to restrictions from the way the parts are assembled, etc. That is usually the determing factor for me to decide to switch to the hand squeezer instead of using the air squeezer.

Make yourself some test pieces out of the trim bundle that also comes with your empennage kit and practice with the rivet sets on either end of the squeezer with rivets inserted in either side of the practice piece, which should be clamped securely in place to prevent it from moving. I use my table vise for this and it works well. You will need to develop this skill moving forward with the project. I cut my practice pieces to about 1.5 x 4 inch strips from .028 or.032 trim bundle pieces and then mark holes about every 1/2 inch or so, then drill, debur, and dimple multiple holes in each piece (dimpling not ncessary for AN470 rivet practice of course). I have many of these practice pieces scattered throughout my workshop, and I reuse them whenever necessary. One last bit of advice, make sure you clamp the work down well when squeezing. If the parts move even the slightest bit when the ram comes up it can have the same affect your pic is showing.

Whomever mentioned abandoning the pneumatic squeezer in favor of more control with a hand squeezer or even a rivet gun in certain areas of the build - I am in 100% agreement with that as well, after having experienced many other disappointing problems while trying to use the air squeezer. One thing that I did discover about the air squeezer is that if you back off the pressure from 90 psi (recommended by the tool maker) to about 70-75 psi, that does help with the control a bit more, and it still has enough oomph to smash the rivet down.

Practice practice practice, and KPR!
 
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And, unless you've already mastered it, go ahead and drill out the rivet on your practice piece. It's a skill most of us needed!
 
Put a rubber grommet over the tail before you squeeze. As the squeezer starts to "squeeze" the rubber will compress all the parts together and then the shop head will form. Works great. You can get a bunch of them at HF for cheep. Hopefully I explained that correctly.
This is good advice. Clear vinyl tubing cut to an appropriate length (just longer than the exposed shank of the rivet) is a good substitute.
 
You have recieved some great advice. Honestly though, it looks acceptable, from an airworthiness stand point. Get a copy of AC-43-1b, or other resource. It will show you how to check to see if the rivet is ok by how much space there is under the rivet head. It looks like there isn't any from the pics, only the material around has lifted, which will happen if not adequately clamped or supported.
I am not saying you should leave it. It is easy to fix per the other suggestions given but it is probably just fine "as-is" too.
I think your rivet set looks just fine.
 
We used to call it "shanking", if you can get a .002 -.003 feeler gauge between the sheets and hit the rivet "shank" then it needed to be redone, otherwise it was acceptable.
 
Thanks for all the info and suggestions.

There was no sheet separation at the rivet shank, just around the edges of the flange tab. I drilled it out anyways (more for practice than anything). Then, I flattened the flange tab so it clecoed to the surface nice and flush. Re-riveted with the squeezer, making sure to keep good pressure on the factory head, and the results were much improved.

After setting all the skin-rib AN426AD3-3 rivets with the squeezer, I've got a much better feel for technique and keeping things square. The trigger on the squeezer is actually surprisingly good for feathering the ram out to make contact and line things up, then adding power to set the rivet. Now, I think I'll need a thin-nose yoke to set the last 2 skin-rib rivets on the trailing edge. Pretty tight space...
 
Seems like over-setting a bit might be the culprit.

The strange thing is that the shop heads of both those rivets fit inside the rivet gauge. Because of that, I didn't think I was over-setting.

Make sure you're using the slots on the rivet gauge according to the shank diameter (the first number in the rivet size), not according to the shank length (the second number).

Earlier this year there was a post from a new builder who misunderstood how their rivet gauge worked. It went something like this: They installed an AD3-4 rivet, and found that they had to drive it a bit more to make the shop head fit the -4 slot on the gauge. Then when they drove an AD3-6 rivet, and found that the shop head was way too small to fit the -6 slot on the gauge. In truth, they should have been been using the -3 slot on the gauge for all AD3-x rivets.

Thanks, Bob K.
 
Make sure you're using the slots on the rivet gauge according to the shank diameter (the first number in the rivet size), not according to the shank length (the second number).

Earlier this year there was a post from a new builder who misunderstood how their rivet gauge worked. It went something like this: They installed an AD3-4 rivet, and found that they had to drive it a bit more to make the shop head fit the -4 slot on the gauge. Then when they drove an AD3-6 rivet, and found that the shop head was way too small to fit the -6 slot on the gauge. In truth, they should have been been using the -3 slot on the gauge for all AD3-x rivets.

Thanks, Bob K.

I can imagine that would lead to some awfully flat rivets ;)

I was using the -4 hole, as those rivets are AN470AD4s. Based on reading [a lot of] posts on here, I now understand that there is a mil-spec which gives the minimum shop head diameter as something less than the ideal 1.5x indicated on the rivet gauge. Based on this, I'm targeting a snug fit of the shop head into the rivet gauge for a "perfect" rivet. In my experiences with the practice kit, it seems like a very careful balancing act to meet both the minimum diameter and minimum thickness requirements.
 
I can imagine that would lead to some awfully flat rivets ;)

I was using the -4 hole, as those rivets are AN470AD4s. Based on reading [a lot of] posts on here, I now understand that there is a mil-spec which gives the minimum shop head diameter as something less than the ideal 1.5x indicated on the rivet gauge. Based on this, I'm targeting a snug fit of the shop head into the rivet gauge for a "perfect" rivet. In my experiences with the practice kit, it seems like a very careful balancing act to meet both the minimum diameter and minimum thickness requirements.

Get your hands on the mil spec. Gil?
The acceptable tolerances are huge, no balancing act required. I do not like the gauges as they are miss used often. Use a micrometer to measure, note how they look, and after a little while you will know just by looking if it is set correctly.
Just for fun, squeeze a few to both sides of the acceptable range. You will be shocked at how much can be tolerated.
Another little trick for rivets you can not see, use your thumb and press down on the shop head. You can then measure the imprint left on your thumb.
Double check every once in a while and you are good to go.
 
Graham,
I would also suggest that while you are working on the practice pieces that you work on the rivet gun skills.
Later you will find that the squeezer is the go to when possible but there are times where you will need the gun. You will find that after a few hundred rivets you can do the squezzer with your eyes closed for a perfect squeeze but the true skill is needed for the gun. That takes a lot more practice.
 
Get your hands on the mil spec. Gil?
The acceptable tolerances are huge, no balancing act required. I do not like the gauges as they are miss used often. Use a micrometer to measure, note how they look, and after a little while you will know just by looking if it is set correctly.
Just for fun, squeeze a few to both sides of the acceptable range. You will be shocked at how much can be tolerated.
Another little trick for rivets you can not see, use your thumb and press down on the shop head. You can then measure the imprint left on your thumb.
Double check every once in a while and you are good to go.

I grabbed the mil-spec and did some measuring with digital calipers. You're right... the tolerances are quite forgiving.

I'm sure that thumb trick will come in handy. Thanks!
 
Graham,
I would also suggest that while you are working on the practice pieces that you work on the rivet gun skills.
Later you will find that the squeezer is the go to when possible but there are times where you will need the gun. You will find that after a few hundred rivets you can do the squezzer with your eyes closed for a perfect squeeze but the true skill is needed for the gun. That takes a lot more practice.

I've been trying to get practice with the gun as well. Back-riveting the stiffeners was super easy and gave very consistent results. Then, I had good results riveting the skins to the spar with AD3-3 rivets, although the shop head thickness was under spec... A closer look at the drawing, and I noticed the plans called out AD3-3.5 for those locations :mad:.

After reminding myself to read the drawings, and getting some good practice drilling out AD3 rivets, I went to set the AD3-3.5s. This time, I couldn't get a good shop head to save my life. I wound up with an entire row of clinched rivets. I could swear I was holding the bar square to the rivet shank, but I think I may have been pushing too hard on the tail with the bucking bar.

Can pushing too hard with the bar lead to clinched rivets? :confused:
 
I've been trying to get practice with the gun as well. Back-riveting the stiffeners was super easy and gave very consistent results. Then, I had good results riveting the skins to the spar with AD3-3 rivets, although the shop head thickness was under spec... A closer look at the drawing, and I noticed the plans called out AD3-3.5 for those locations :mad:.

After reminding myself to read the drawings, and getting some good practice drilling out AD3 rivets, I went to set the AD3-3.5s. This time, I couldn't get a good shop head to save my life. I wound up with an entire row of clinched rivets. I could swear I was holding the bar square to the rivet shank, but I think I may have been pushing too hard on the tail with the bucking bar.

Can pushing too hard with the bar lead to clinched rivets? :confused:

You don't need to push hard on the bucking bar. However, two things to look for. Measure the rivet protrusion, should be 1.5 diameters or so. Make sure your work is clamped down, supported in a solid manner and not allowed to move. Most of the time I see this when the part is not solidly supported.
 
You don't need to push hard on the bucking bar. However, two things to look for. Measure the rivet protrusion, should be 1.5 diameters or so. Make sure your work is clamped down, supported in a solid manner and not allowed to move. Most of the time I see this when the part is not solidly supported.

Work was definitely clamped down to the bench. I learned that one very quickly on the first stage of the practice kit ;).

The tail protrusion looked ok [albeit, to my woefully untrained eye]. Due to restricted access, I couldn't get the rivet gauge in there to get a good measurement on tail length. But, the plans called for a 3-3.5, and I can't imagine Vans would try to mess with your head too much with rivet callouts on the practice kit, right? :p
 
Lighten the pressure of the bucking bar and give it another try. Also, if you drilled out the rivets improperly the holes may have been enlarged. This can cause shop head issues.
Never drill through a rivet, not saying you did, but something to consider.
I can't speak for the new kits, or the practice kit, but rivet call outs on the older kits where not always correct.
 
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I've been trying to get practice with the gun as well. Back-riveting the stiffeners was super easy and gave very consistent results. Then, I had good results riveting the skins to the spar with AD3-3 rivets, although the shop head thickness was under spec... A closer look at the drawing, and I noticed the plans called out AD3-3.5 for those locations :mad:.

After reminding myself to read the drawings, and getting some good practice drilling out AD3 rivets, I went to set the AD3-3.5s. This time, I couldn't get a good shop head to save my life. I wound up with an entire row of clinched rivets. I could swear I was holding the bar square to the rivet shank, but I think I may have been pushing too hard on the tail with the bucking bar.

Can pushing too hard with the bar lead to clinched rivets? :confused:

The most common cause of clenched rivets for me is with the rivet shank being a bit too long. Heh heh, will Van's mess with your rivet call outs in the practice kit? Not that I recall - but they certainly do mess with your head during the build. In fact, you run right smack into that problem on the first rivet assembly of the HS for the center bearing/hinge assembly. I have seen them go both ways so far - a bit too short, and a bit too long at times.

One other possible issue is a combination of too much pressure on the bucking bar and/or too much air pressure on the gun. I have a flow regulator on my gun with settings from 1 to 6, so I am not much good at quoting actual psi pressures at the gun, but I think it is supposed to be around 30-40 psi for most AN426 AD3 rivets if I recall other posts correctly. 55-60 psi is what I remember for AN470-AD4 rivets. Now a days I just make an adjustment until the timing for setting the rivet "feels" right.

I simply leave my compressor set to 90 psi and make small changes to the regulator at the gun. Try easing off the bucking bar so that you just maintain good contact pressure with the bar and nothing more, and perhaps back off the air pressure on the gun a little at a time and check your results. Note that I said to reduce the AIR pressure to the gun, and NOT the pressure applied with the gun/rivet set against the rivet head. Then let your hand and the bar move with the rivet shank as you drive the rivet, without applying additional pressure on the bar. Pushing the bar too much will almost always result in a clinched rivet because that will cause the bar to slant one way or the other as a result of the uneven pressure applied by your hand, and the rivet shank has no choice but to give in to that force.

I love reading about how you are continuing to work this out... it brings back memories of my own early days.

You are getting there - just keep practicing.
 
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I simply leave my compressor set to 90 psi and make small changes to the regulator at the gun. Try easing off the bucking bar so that you just maintain good contact pressure with the bar and nothing more, and perhaps back off the air pressure on the gun a little at a time and check your results. Note that I said to reduce the AIR pressure to the gun, and NOT the pressure applied with the gun/rivet set against the rivet head. Then let your hand and the bar move with the rivet shank as you drive the rivet, without applying additional pressure on the bar. Pushing the bar too much will almost always result in a clinched rivet because that will cause the bar to slant one way or the other as a result of the uneven pressure applied by your hand, and the rivet shank has no choice but to give in to that force.

I've found that the pressure setting "at the gun" with the mini-regulators/flow regulators aren't always that repeatable. I've put an explicit regulator (with gauge) in line for rivet gun ops. For size 3 rivets, I've found with my 3x gun that 35 PSI works well (about 5 hits from the gun sets the rivet nicely). With the chepo on gun regulator, I could easily have the pressure set too high and then have have the set bounce all over my work!
 
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