aja wrote
how about putting some plumbers tape (the thin white polytetraflouroethelene stuff or whatever it is called) around the shaft and wedging the knob onto it?
Hmm.. This is not really a solution, I've tried. Once you over-turn it (which will be like the 1st time), everything just falls apart and and the knob just comes off. You'd have to use something harder with less give and that doesn't deform as easily, like paper, or tape. Try taping the shaft up with masking/electrical tape and then forcing the knob on. Thing is its always going to give you kak.
I'd say the only sustainable solution is to get split shaft pots. There's a reason why these things use such intense fixing methods, the moment arm of the knob relative to the shaft is massive. This makes it almost impossible for a quick fix.