Now that I am about to finish my -9A wings, I think I have finally overcome my struggle with shooting AN4 long rivets. The key is clearly high air pressure at the gun and duct tape on the tip of the rivet set. I am using about 64 lbs. of pressure to shoot (3X gun) the big rivets with a straight set and about 68 lbs when using the offset set. This sounds like a lot, but is what I'm finding works best for me. Any less, and you have to hit the rivet too many times and the metal work hardens and will simply stop compressing because it is now too hard. You can clearly see this happen while you are shooting the rivet. With higher pressure, you hit it much harder fewer times, and the rivet is properly set by the time it is hardened and won't go any further (keep hitting it after it has hardened, and it will start to crack or fracture).
Earlier in my construction, I think I was a little too timid to crank up the air pressure and always battled AN4 rivets when I had to shoot them with the gun. Like those AN4-9 (or so) rivets in the empennage spar hold down brackets. I fought with those things; if I had just cranked the air pressure way up...
Earlier in my construction, I think I was a little too timid to crank up the air pressure and always battled AN4 rivets when I had to shoot them with the gun. Like those AN4-9 (or so) rivets in the empennage spar hold down brackets. I fought with those things; if I had just cranked the air pressure way up...
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