rivet problem - need advice

lostpilot28 · #1 12-26-2006, 11:42 AM

I think I need to upgrade to a better quality squeezer, because I think it's flexing when I squeeze rivets. I've attached a couple of pictures of some rivets on my left elevator and I'd like to get some opinions on what I should do.

My concern isn't that they're not pretty, but that they may not be strong. Basically, no matter how straight I try to hold the squeezer the shop-heads end up squeezing more to one side of the hole leaving the other side unattached to the rivet. I've drilled a few out and replaced them and they look like little feet instead of nice, round mushrooms.

Do I need to start drilling all these out? Any advice is greatly appreciated.

Regards,
Sonny W.
RV-7A empenage

scard · #2 12-26-2006, 11:59 AM

You're right. Those don't look so hot. (the camera always makes things look worse than they are). Maybe some more practice with the squeezer is in order. Try experimenting with squeezing off center a number of ways (just a hair). Pneumatic or hand squeezer? The yoke does flex a bit. The bigger the yoke, the more flex.

Stephen Lindberg · #3 12-26-2006, 12:07 PM

Concentrate on holding the squeezer EXACTLY perpendicular to the rivet. I doubt this is a fault of your tool. Those rivets look a little undersqueezed to me. I would not replace the ones you have shown us, but give them a few thous more squeeze (after you measure the shop heads and verify my observation, natch). Better is the enemy of good, rivets don't have to be perfect, and you can cause more trouble for yourself drilling out less than perfect rivets. Really, those look like airworthy shop heads as is. Good luck.

Pirkka · #4 12-26-2006, 01:07 PM

I had similar problems with rudder skin against main spar (stiffener and it's rivets blocked perfect access to some of the rivets). I concentrated too much to the shop head side and tried pretty much everything. I managed to do more bad rivets than even since in very short time. Then a time out -- now I tried again, but didn't look at all at the shop head side (of course, I had already correct shop head height adjusted). I went to the manufactured head side, put the squeezer as well to the center of manufactured head as possible, then looked that squeezer was perpendicular to the rivet and squeezed. There must be numerous ways to check the perpedicularity of the squeezer, I do it by looking the mirror image which is reflected from the skin (anything perpedicular to the mirror should like going through it without making any angle at point of "touch"). So far with good success. After this the hardest rudder rivets went fine.

It's possible that the cheapest squeezers/yokes bent more than expensive ones but there are numerous ways that the user can do it by itself.

So before going to buy new tools, try different methods. If you have smaller yokes which has access to those rivets, try again with them. Longer yokes are more likely to bend.

I will not comment about drilling those out more than I would do so, if they are in critical place. I wouldn't say they fulfill mil. spec. so if that is what you are following, start your drill....

It would be very nice to know how much rivet like that can hold compared to the rivet done according to the mil. spec. How big difference rivet like that can make?

Pmerems · #5 12-26-2006, 01:18 PM

What size (throat depth) yoke are you using? Brand?

Paul

Brantel · #6 12-26-2006, 01:19 PM

What squeezer and yoke you using?

I would say you need to drill them out because you have several clubed over in a row. One here and there I would not worry about but an entire row of them would make me nervous.

I also noticed from the pics that it does not seem like (can't tell for sure in a pic) you have debured your edges. This can lead to cracks later down the road.

szicree · #7 12-26-2006, 01:19 PM

It's important to get the rivet centered on the die to avoid this problem. The other big thing is to use the smallest yoke that will reach. The deeper yokes definitely flex quite a bit.

gbrasch · #8 12-26-2006, 01:19 PM

I would also double check that you are using the correct length. If they are too long, they tend to bend like the ones in your photo.

GAHco · #9 12-26-2006, 01:24 PM

My best guess is that either the rivets are a little old and hard or that you should try one 1/2 size shorter. I found the 1/2 size different to fix many squeezing issues where the full size just wasn't quite right. Just check the dimensions of the shop head when its done to make sure you are within specs.

Tom

Finley Atherton · #10 12-26-2006, 01:29 PM

I had a similar problem with my pneumatic squeezer with a 3? yoke.
This is more likely to happen if the rivet is a bit too long. I find that it helps if the rivet is located close to the inside edge of the dies when squeezed. I discussed this with Cleaveland Tools some time ago and they said that if the die surface is too slippery it can force the rivet to slide and therefore bend over when squeezing. The recommendation from Cleaveland was to keep the dies clean and to rough up the polished die surface slightly.

Fin 9A
Australia