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Nasty smeared rivet - any tips for drilling this thing out?

N546RV

N546RV

Well Known Member
Photo #1
Photo #2

I'm not exactly sure how I managed to nasty this thing up so bad, but I'm 99% sure this needs to be replaced. Problem is, that manufactured head is so far off center that I'm really skeptical of trying to drill it out from that side. I guess maybe the best bet is to start with a #40 and try drilling it from the shop head side?

:mad:
 
My thoughts would be to try to machine off the shop head with a rivet shaver bit in a cage and then trying to punch out the remainder.

Alternatively you may be able to set your #40 bit to go just short of the flange surface and use the end of the bit to break off the head as you still have a centre dot in the head to guide the drill bit.

If it is really fouled up, you still have the option of enlarging the hole for - 5/32 rivet or a #8 bolt and nut.
 
Mark Albery said:
If it is really fouled up, you still have the option of enlarging the hole for - 5/32 rivet or a #8 bolt and nut.
Click to expand...

Hmmm. Looks like this is a rib flange to spar joint so I would be very wary of drilling out to a larger size. I'd go with the option of grinding off the head and punching out the stem. That way, if it gets screwed up, the worst case is you have to replace the rib.
 
As long as you maintain proper Edge Distance, going oversize isn't a big deal.
But with careful removal, you should be able to avoid it.
 
It's ugly and marginal but it might be ok- see if you can live with it for a few weeks. Unless you have a ton of experience, the odds of not enlarging the hole are not good. The rivet guidelines allow 10% marginal such as your mashed head. I notice the one above it has the same rivet set dance on the manufactured head also; you need to sharpen up your riveting skills. :) The first thing is to analyze your technique, think about what went wrong. The wing ribs are best set with an offset set, not the shorty but the mid-range size (7"?). Start with low setting forces by slowly ramping up the force with the rivet gun trigger, using short bursts, fingers of one hand steadying the set end next to the rivet, the other hand with FIRM, ROCK HARD steady pressure pushing straight down. Really focus on this aspect. It helps to physically get your shoulder behind the gun. Think shoulder, firm pressure, short bursts, lower gun flow settings that will still set the rivet. Are you using the external brass flow setter into the gun? I also use duck tape on the set at the rivet gun end to help the set from rotating- the rotation causes you to focus on the wrong thing at a critical time. If you want to drill it out after a few weeks, center punch the head (best guess), angle drill, small drill like maybe #42, drill shallow, maybe 1/16". If the hole is off center, use a needle file to move it. Once you think it's ok, open up to 1/8" and pop the head off. Consider using a wood block, with a guide hole drilled in the drill press, to get the angle drill perpendicular since the angle drill is not easy to drill square. Once the head is off, you will need to drill out some of the shank with the #42 drill to be able to punch the rivet out of the hole since there is a long grip. Again, use the center punch to get the #42 started in the middle of the shank. This won't be easy so make sure you really need to remove it. Good luck!
 
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A very sharp high quality wood chisel, driven by a light weight hammer, is quite effective for removing rivet heads. Then it's easier to see the center of the rivet shaft to drill & punch it out.

Is it an illusion, or is the flange standing 'proud' of the spar surface? If it is, I think that the gap between the flange and spar is a bigger deal than the rivet head issue. It can cause issues with alignment of the prepunched skin holes, and more important, put the rivet shaft in bending load instead of tension & shear.

Charlie
 
I would leave it alone. It is only 1 rivet out of many thousands and your airplane will not care if you leave it. Just my 2 cents and Alcoa's.
 
rv7charlie said:
A very sharp high quality wood chisel, driven by a light weight hammer, is quite effective for removing rivet heads. Then it's easier to see the center of the rivet shaft to drill & punch it out.
Charlie
Click to expand...

Charlie - I agree and have done this to remove lots of universal and round rivet heads. It works well if you have a solid under structure, like a spar cap, heavy stringer or longeron, etc... It looks like this would be a good method for this one.
However, I would not try this on .025 skins riveted to an .025 rib. Even .032 is marginal. You can end up "denting" the hole enlarging it, or worse, tear the skin. (I have the badge)

If I feel I can not drill the head to the depth I need to snap it off, I will go to the shop head side. Just make sure you only drill it to a depth that does not penetrate the skin. It is nearly impossible to find the center of the shop head. They almost always have some drift off of the center of the hole.
 
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Hard to see what working room you have, but looking at this rivet it should really be replaced. Photo 2 makes it look difficult to imagine good attachment albeit an imperfect rivet.

That said, the hole is really vulnerable since the head as set is displaced so much from the center. If there's room, I'd probably try to grind off as much of the head as possible taking plenty of time (there's much opportunity for the cure to be worse than the disease). Then remove the rib. I wouldn't worry too much about the rib but I would be concerned about the spar. If the flange on the rib gets nuts'd up, ribs are pretty inexpensive or the flange can be replaced if you decide to go that way.

Be careful "punching" out the stem - it's easy to get some damage to the hole with that approach. See if you can't get the shop head to rotate a bit in the hole before you try that - maybe even grab the shop head and pull it out.

Dan
 
I tend to agree with the "leave it alone".

But why listen to us? If it's important, send your pics to Vans and get their opinion. You might want another showing more of the entire area for context.
 
samray said:
It's ugly and marginal but it might be ok- see if you can live with it for a few weeks. Unless you have a ton of experience, the odds of not enlarging the hole are not good. The rivet guidelines allow 10% marginal such as your mashed head. I notice the one above it has the same rivet set dance on the manufactured head also; you need to sharpen up your riveting skills. :) The first thing is to analyze your technique, think about what went wrong. The wing ribs are best set with an offset set, not the shorty but the mid-range size (7"?). Start with low setting forces by slowly ramping up the force with the rivet gun trigger, using short bursts, fingers of one hand steadying the set end next to the rivet, the other hand with FIRM, ROCK HARD steady pressure pushing straight down. Really focus on this aspect. It helps to physically get your shoulder behind the gun. Think shoulder, firm pressure, short bursts, lower gun flow settings that will still set the rivet. Are you using the external brass flow setter into the gun? I also use duck tape on the set at the rivet gun end to help the set from rotating- the rotation causes you to focus on the wrong thing at a critical time. If you want to drill it out after a few weeks, center punch the head (best guess), angle drill, small drill like maybe #42, drill shallow, maybe 1/16". If the hole is off center, use a needle file to move it. Once you think it's ok, open up to 1/8" and pop the head off. Consider using a wood block, with a guide hole drilled in the drill press, to get the angle drill perpendicular since the angle drill is not easy to drill square. Once the head is off, you will need to drill out some of the shank with the #42 drill to be able to punch the rivet out of the hole since there is a long grip. Again, use the center punch to get the #42 started in the middle of the shank. This won't be easy so make sure you really need to remove it. Good luck!
Click to expand...

Yeah, I've been using a double offset set for the wing rib rivets. I got through the left wing without any real problems a few weeks ago, but I think this time I got too comfortable and got sloppy.

rv7charlie said:
A very sharp high quality wood chisel, driven by a light weight hammer, is quite effective for removing rivet heads. Then it's easier to see the center of the rivet shaft to drill & punch it out.

Is it an illusion, or is the flange standing 'proud' of the spar surface? If it is, I think that the gap between the flange and spar is a bigger deal than the rivet head issue. It can cause issues with alignment of the prepunched skin holes, and more important, put the rivet shaft in bending load instead of tension & shear.

Charlie
Click to expand...

Good info on the chisel idea - and coincidentally, I just bought a wood chisel set a couple weeks ago for another little project. As for the flange standing proud, I think that's just an illusion from the lighting. It was rather difficult to get a good photo of the area; I ended up holding a flashlight in one hand and the camera in the other. Made for some odd and harsh lighting.

DanBaier said:
Be careful "punching" out the stem - it's easy to get some damage to the hole with that approach. See if you can't get the shop head to rotate a bit in the hole before you try that - maybe even grab the shop head and pull it out.

Dan
Click to expand...

This is the part that worries me a bit. I've found through experience that long rivets like this one really love to grip their hole, and the amount of force required to knock the stem out makes me uncomfortable about fouling up the hole. I *really* don't want to foul up holes in the main spar...

Buggsy2 said:
I tend to agree with the "leave it alone".

But why listen to us? If it's important, send your pics to Vans and get their opinion. You might want another showing more of the entire area for context.
Click to expand...

Yeah, I'm going to do this. Leaving it in would be the "safest" option, in terms of avoiding further damage, but that's something I'd want mothership approval on.
 
Buy a rivet removal tool like this:

1341a.jpg


Very handy. Just aim the tool over the head and it drills down to where you have the stop set. Hopefully, just to the thickness of the head, then you can snap off the head with a punch.
 
flyingreg said:
I would leave it alone. It is only 1 rivet out of many thousands and your airplane will not care if you leave it. Just my 2 cents and Alcoa's.
Click to expand...

Concur..leave it alone....and if it REALLY bothers you, put a new rivet on both sides of it :) Rosie
 
Gil,

I had to remove a rivet similar to Philip's in the first post and the hole ended slightly enlarged. Are there any restrictions to using a solid rivet with a oversized diameter (NAS1242AD4) or would you use a cherrymax rivet instead.

Thanks Jim
 
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Haven't seen it mentioned...when you do drive a rivet out after drilling the head/tail...ALWAYS back up the material with a bucking bar along side the rivet you're driving out. This will prevent damaging the hole and the area around it.
Obviously, this requires an extra set of hands.
 
If you can get to the back of the rivet with ease I would drill the buck-tail with a #40 then use a good chisel with a light hammer to remove the tail, then back the rivet up with a bucking bar then punch the rivet out. If you have to go at it from the front side I would use a rivet shaver or a counter sink cage with a rivet shaver set, set it to flush with scrap material then shave the head.
 
Grind it

My A&P was a master at aluminum work. He would grind the machine head off and push the rivet out.

Look at the hole. If you could, redrill and put a another rivet in such as a structural blind rivet. Or even a AN3 bolt.

Purpose is to make structurally sound.

If not, drill smooth to avoid any potential cracks and rivet next to the hole.

Best part is this looks hidden. Only you will know.

Fix it for strength and safety and not for beauty.

Remember that better is the enemy of good enough. Sometimes the fix is not always what it is cracked up to be.
 
Driving '67 said:
Gil,

I had to remove a rivet similar to Philip's in the first post and the hole ended slightly enlarged. Is there are restrictions to using a solid rivet with a oversized diameter (NAS1242AD4) or would you use a cherrymax rivet instead.

Thanks Jim
Click to expand...

I think it's OK since the rivet would expand to fit....

However, since the initial rivet was screwed up, there is a good chance that a second rivet would do the same, especially with an irregular hole.

I just think the safest, and easiest, is to admit a solid rivet re-do is risky and just blow the 75 cents odd on a structural pulled rivet - an oversize Cherry Max - into a cleanly re-drilled hole.
 
Update: Scott at Van's recommends replacement. I think I'm going to try grinding the head off with my Dremel tonight.
 
Which dremel attachment is best for grinding rivet heads? Especially if they are in a tight spot?
 
Dremel

diamond said:
Which dremel attachment is best for grinding rivet heads? Especially if they are in a tight spot?
Click to expand...
If you really want to use the dremel, get a small piece of scrap and drill a hole in it the size of the shop head. Slip it over so if you slip, the wheel won't scar the spar.
I use a cutting wheel often to grind by using the edge. I also have a few of these carving bits that work well. http://www.dremel.com/en-us/Accessories/Pages/SubCategories.aspx?catid=2070&catname=High+Speed+Cutters
 
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Yup, the speed cutters work great, but as Larry points out, take care that you don't damage something if the bit slips off, because it will slip off if you're not careful.

I ended up damaging and replacing the rib in question here. It gets especially difficult to remove the head with a Dremel once you get close to the flange. There's a very fine line between the rivet head and the underlying material!
 
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