As a mechechanical designer I can safely say that a set screw, even tapped in plastic, will hold fine for this application. The question is can it be assembled with a set screw (ie can you get to the screw head to tighten it while the knob is in place)? A trick I've used is to score the shaft if a friction fit knob is loosening. I don't know how accessable this shaft is but a hardened prick punch (no, that's not what you do to someone hitting on your wife in a crowded bar in New Orleans) should do it. Even some 60 grit sandpaper or a steel dental pick can work. Try to get the scores running with the axis of the shaft. Be sure you support the shaft when scoring, it was not meant to take you pressing it sideways with all your might.

If you are REALLY careful you can also use an anaerobic thread lock (Loctite to you & me). The gotcha with this is if it gets into the workings of the switch you are HOSED. The Red is permanent, but Blue is probably sufficient. Try putting the smallest little bit (I'd use a medical syringe or a tiny drop on the end of a pin) in the hole near the bottom and get it on the walls a little. I was looking at the breakaway specs for this stuff earlier today, but I'm not a big enough weenie to actually have remembered the numbers.

I haven't had this happen to me yet, but I'm not to worried (I can order a new one from an stereolith house and get in under the radar for about $120 - after I model it of course).

Good luck. Radio shack knob on a new empeg...the HORROR...

;-)

-Zeke

just say you weren't paying much attention...