Floorpan rivets are "waffle" set. I assume you have a waffle bit for your gun. I have set a fair number of 3/16" floorpan, seat frame, etc rivets. I used an air hammer initially and the results were OK, but not great. I bought a 3X rivet gun on eBay and it works better since it has a much longer stroke. The real key is to "set" the rivet in one operation. I set them cold. If you go back a second time on the rivet, the results are not very good, as it messes up the waffle pattern. I use 80# of air pressure for my rivet gun, which seems to work well. I tried less and that didn't work as well. Having a good "buck" is important to get a good rivet set. I made a setup to use a 1" solid rod, a 1" pipe to put the rod in and a press plate on the floor to serve as a very solid "buck". If you want to see some pictures of my setup, send me an email to:
[email protected].
Rusty Nelson