[Echo Tango]

Building my -7A Empenage kit right now, and while I was finishing up the horizontal stabilizer I was having a bit of trouble getting one of my rib flanges to seat itself flush against one of the spar webs. Naturally, I put a cleco in the bottom hole of the rib flange into the spar, thinking it would sufficiently snug up the top hole. Nope! Still a gap!

So I decided I would put the rivet through both and "drive it" slightly to widen the rivet shank an eency weency bit (in order to provide a "tighter" fit). I then proceeded to place my bucking bar against the rib flange (near the rivet in question) and drove the manufactured head with my gun softly. It worked! The flange slid the rest of the way down the rivet shank and held it tightly against the spar and provided enough "holding friction" to keep the skins together. I then drove the rivet to final specification.

Question is: is this a bad practice? I did it again on the lower rivet, as that part of the flange wouldn't sit flush either, and it worked flawlessly.

 

[vlittle]

Try this:

Purchase rubber grommets that will push on to the shank of your rivet. You may have to slice them in half to ensure that they stand proud of the rivet shank a little bit. The friction of the grommet will hold it in place.

When you buck the rivet, the bucking bar will compress the grommet and force the faying surfaces together. Give it a bit of a hit with the rivet gun so that the rivet swells and clamps the faying surfaces together. Remove the grommet and finish riveting.

 

[DaAV8R]

Good technique

The technique you describe is good technique in my opinion and demonstrates you have very good control of the gun and the bar. Some of the very experienced old time mechanics recommended this same technique to me.

 

[Andrew M]

It works

If you got this worked out then I imagine you know what the risks are. I prefer to use a piece of weatherstripping on one face of my bar, similar to the grommet idea. It acts like a back rivet set, except it's the bar side. The foam rubber holds everything clamped until the rivet is swollen enough to hold it, then finish bucking without the foam rubber. Less risk, same reward.

 

[Echo Tango]

If you got this worked out then I imagine you know what the risks are. I prefer to use a piece of weatherstripping on one face of my bar, similar to the grommet idea. It acts like a back rivet set, except it's the bar side. The foam rubber holds everything clamped until the rivet is swollen enough to hold it, then finish bucking without the foam rubber. Less risk, same reward.

this makes sense. what are the "risks" you speak of? didn't notice any abnormal wear on the shank or anything.