This is a tricky one. I use a flanging tool that Rene made himself especcially for the air tubes.
I believe that one FC member reported that he fixed one air tube by re-flanging it himself, but I can't remember how he did it.
After using Rene's tool, I can't think of what else I could use, mainly because these air tubes are so tiny and fragile. The tubes are also stepped inside, so you need a metal rod inside to hold it and put pressure on it on that side while you flange the tip, on the inside of the bowl.
The flanging tool actually bends the tube outward (convexly), which tightens the grip of the tube to the the crucible (bowl).
Here's the image of the tool
(from this page:
http://www.vapman.com/en/swiss_quality):
Air Tubes:
I've fixed two vapmans with similar issues. One that had an air tube come off completely - the abused vapman I posted here before, and another one who had I think 2 tubes damaged and I replaced all three tubes and the bowl as well.
I've also tightened the tubes on my orginial vapman once. It's very old and it had two air tubes that were just a little bit loose. It really didn't needed it, but I used it to practice on.
It's not a terribly difficult thing to do, but requires finess (a feel for what you're doing) so you don't crack the air tube at the tip (where it's flanging). Just having the tool will not ensure you get it right the time, or two -- don't ask me how I know this... shhh.
I can do this easily but the pain is the shipping costs - almost $6 each way, if you use Priority Mail.
I had given this some thought before Rene sent me the tool, but never came up with a worcable idea. I know Rene would not recommend using anything else -- Maybe OF can think of something?
I know this is not what anyone would like to hear on this, but the air tube setup is very precise.
Hope this helps.