Squashed rivet heads

I am driving 470-4 rivets in the aft section of the fuse and they are giving me fits. The heads are turning in to sunny side up fried eggs i.e. the edges of the round head are getting squished out. I have tried 3 different sets but it makes no difference. I am running 50 psi on a 2x gun. I am doing it alone and the bucking has to be done inside the fuse so I can't see bar so I am going blind. Any idea what that could be? I am doing my best to hold the gun straight.

Any wisdom gladly accepted

Scott

Drop down to about 40 psig. Use two layers of masking tape over the rivet set. Replace the tape after three or so rivets. Hold the bucking bar between your fingers and thumb such that the tips of your fingers and tumb overhand the bar and touch the skin. You can feel when the bar is perpendicular and when the shop head is done.

Carl

Ok I'll give that a try thx.

Could part of the problem be the 2x gun? I think that most of us used 3x guns, even driving 3/32 rivets. The lighter the hit, the more hits it takes to set a rivet. More hits, more chances to bounce off the factory head. Also, more chance of work hardening the rivet before it's completely set, making it harder to set, (rinse & repeat...)

Just a thought...

That's possible. I don't have a 3x. I'll try to borrow one.

I really thought long and hard and tried a number of things. I think I have developed a habit of letting the pressure off the gun before I have fully released the trigger. It really doesn't take much to make a mess of the rivet. But perhaps I need a bigger gun. I have had a couple work harden on me. I have been doing mostly -3s up to now.

Thanks for the suggestions.

In my kit, all the -3's were flat head. Much easier (at least for me) to avoid problems when using a mushroom set than when using the universal head set, even on -4's. I have had the same problem on universal heads, releasing pressure before the gun stops.

Charlie

You need a 3Xgun - You are driving the rivet for too long with not enough force and deforming the manufactured head - not the shop head.

http://www.browntool.com/Default.aspx?tabid=344&CategoryID=37&Level=a&ProductID=127

I use a old Cleco gun for all my -3 rivets. Anything bigger ... I bought the 3X linked to above and not had a problem.

A heavier bucking bar may help, but after using a 2x gun for almost everything I found a borrowed 3x gun was needed for longer 1/8 rivets on the fuselage, especially if they were countersunk.

I agree that a 3x gun is preferable for 1/8" rivets, but I was happy with my results using a heavy bucking bar and a 2x gun at 60 psi.

Now one question ... I wonder if all 2X guns are the same ? Sure, build quality of the gun will differ .. but will a top of the range industrial gun give better result than I cheap 2X clone ??

I'd say that a better tool will often do a better job, but it doesn't necessarily mean that a better *wrong* tool will do a better job.

One other thought about riveting in general and especially about 1/8 rivets: This will seem counter-intuitive, I found that if i had the overall structure sitting on a rigid support, I had a lot more trouble driving universal rivets and was damaging a lot more factory heads. I found that if I placed the structure on something like a moving blanket, or better, a piece of stiff foam rubber (foam rubber carpet padding worked great), I got much better results. My belief is that if the structure is on something solid, it can't move enough to allow the rivet to be driven into the bar so I was just hammering on the head. If the structure could move just a bit, the rivet tail could hit the bar hard enough to start and maintain the 'oscillation' between the 'spring' (my hand/wrist)-loaded bar and the driven rivet. In a perfect world, the rebounding bar moving back toward the rivet as the next blow hits can effectively increase the driving force, without upping air pressure.

Or maybe I'm wrong.

Charlie

edit: The advantage of the foam rubber over blankets, etc is that it limits skidding sideways, but allows vertical movement.

Bigger Rivet - More Pressure

With my 3X gun I run 40-60 psi for 3/32 rivets and 90 psi for 1/8 rivets. With a 2X gun at low pressure you are getting work hardening of the aluminum rivet. The longer you hit the rivet the worse it gets, and the harder it is to get a properly set rivet. Best to try to have a fully set rivet on a count of "one potato-two potato-three potato".