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Rivet hole conundrum

georgemohr

Well Known Member
Hi all!

Here's a scenario: You are riveting a doubler to a spar with five AD4 universal rivets. You cleco and match drill the holes to #30, then disassemble and deburr. Putting the parts back together with clecos you begin riveting. You find that the fourth rivet will not quite fit in its hole. Perhaps some small error during match drilling caused some tiny misalignment.

Now the conundrum: how to deal with this. The obvious fix it to re-drill the offending hole, but we will be unable to deburr both sides of both parts because the parts are already partially riveted together.

So the question, is it acceptable to re-drill in situ and just deburr the outer surfaces? Or must we fix the hole in a more nuanced way, perhaps with a small file? Or must we drill out all these rivets (pls dont say yes to that LOL).

TY!
George

P.S. I have this problem on the practice kit, fortunately hehe
 
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Run your #30 reamer though and rivet. The shank will swell to fit the small irregularity.
 
Misalignment

How far is it off? That shouldn't happen if the parts were clekoed during the match drill process. If the holes are #40 and need to be #30 then use #40 clekoes and swap them to #40 after a hole is enlarged. It's the practice kit. Drill it. Rivet, drill it apart, reassemble, repeat.
The other and more common problem is a burr in the hole. I use a screw bit on a speed deburring tool to clear the hole.
 
Just push an awl through the hole and it will squeeze open the hole just a tiny bit for the rivet to fit through. If you can tap the rivets through the holes with the bucking bar, you should be good. The rivet will swell up and cover the hole. This is also a reason to use more clecos to clamp the sheets down as you rivet to minimize the tiny movements as you work. This is sheet metal work and not CNC. Even the temperature differences between the two sheets will move the holes slightly. You will notice this more when you start working on the wings.

I know at least one builder who feared making mistakes that he delayed his progress for years for simple issue like this. This is something everbody experience before. Build on.
 
What Mike said.

Note that in the rivet spec on Van's pages, it specifically says you don't need to debur between mating parts - I think the spec's assumption is that you don't disassemble the assembly before riveting, but it doesn't make that clear.

Dave
 
I was taught to make the first two holes of a riveted assembly "locator holes."

Cleecos are inadequate for accurate location. The holes are enlarged and the clamp/mandrels undersized and not concentric.

Drill the first two holes (opposite sides/corners/ends) in 1/8" or .125" and insert -4 rivets, then proceed to do the balance in #30 until everything is drilled out - then #30 to the original two.

FWIW
 
Awl or Drill

Pushing the awl thru works almost every time. But if the drill motor is in my hand I just push the drill but thru without running the motor. Works about the same. And yeah, I clecos seem to be just a little approximate sometimes.
 
I was taught to make the first two holes of a riveted assembly "locator holes."

Cleecos are inadequate for accurate location. The holes are enlarged and the clamp/mandrels undersized and not concentric.

Drill the first two holes (opposite sides/corners/ends) in 1/8" or .125" and insert -4 rivets, then proceed to do the balance in #30 until everything is drilled out - then #30 to the original two.

FWIW

I would add after drilling to final size and prepping for final assembly, re-assemble using a few rivets to align the holes and then install the clekos.
 
I'll point out that, if we're dealing with flush rivets, the hole will enlarge in the process of dimpling to about .148", which brings us back to the original problem - in a way.

The nesting of the dimples tend to "take over" location contributions.

Good practices prompts the builder to evaluate the order of rivet clinching - bore-sighting the holes as riveting progresses to see if a misalignment is being created.

FWIW
 
Clarification
Awls are typically tapered. So unless you use a tool with a point that transitions to a constant diameter that matches the original hole diameter, we would not recommend this type of process to adjust a hole to allow for rivet insertion. I.E., don't use a tapered awl.

If the mis-match is small, the best option would be to use an appropriately sized reamer which will leave a nice internal surface finish where not being able to deburr should not be a problem.
 
Clarification
Awls are typically tapered. So unless you use a tool with a point that transitions to a constant diameter that matches the original hole diameter, we would not recommend this type of process to adjust a hole to allow for rivet insertion. I.E., don't use a tapered awl.

If the mis-match is small, the best option would be to use an appropriately sized reamer which will leave a nice internal surface finish where not being able to deburr should not be a problem.

Well this is a relief. It's what I've been doing the whole time. Usually I'm just cutting out primer that's gumming up the holes. Hard to argue with such a reliable source.
 
I keep a bag of blunt drill bits and use the shanks as alignment pins. Three pins before you start clecoing ensures perfect alignment.
 
I would add after drilling to final size and prepping for final assembly, re-assemble using a few rivets to align the holes and then install the clekos.

Excellent tip, thanks! Indeed the clecos are not quite precise enough to prevent a bit of 'creep' in the alignment of the parts.
 
George,
I've never run across this issue after match drilling, so something may be amiss with your technique. I cleco every #40 hole, then remove each cleco one at a time, match drill #30, then recleco with the next sized cleco. If you run across the same issue again after carefully demurring each hole, then try a different rivet. Good luck.
 
I find this constantly with primed parts and AD4 universal head rivets - never on AD3 though. Don’t know if it’s something to do with the smaller tolerances or something.

I usually try and align the holes with a straight 1/8” punch first, then if that doesn’t work I try and tap the rivet in using an automatic centrepunch on the dimple in the rivet. It usually goes in in the first 1-2 pops. If it doesn’t I pull it out and use a #30, 4 flute straight reamer.

Be careful tapping it in - you can bow the flanges apart. You can usually feel if it isn’t going to go in easily and needs a lot of force and I stop and use the reamer. I always back it up using my fingers or a small block of wood with a hole in it. A lot of the time it’s because I haven’t got the rivet normal to the hole when I put it in.
 
Cleko

George,
I've never run across this issue after match drilling, so something may be amiss with your technique. I cleco every #40 hole, then remove each cleco one at a time, match drill #30, then recleco with the next sized cleco. If you run across the same issue again after carefully demurring each hole, then try a different rivet. Good luck.

Same here. It's rare and usually due to a shard or some primer. A twist of a reamer works every time.
 
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