TenTec makes some mighty fine equipment, but their knobs leave a lot to be desired. It's possible to crack the plastic knobs if you over-tighten the setscrew. And - for a knob that goes onto a bandswitch - it's hard not to over-tighten the setscrew. This situation is what lead to my looking into repairing, rather than repacing, the knobs.
I researched the shelves of the local hardware, automotive, and grocery stores looking for a good adhesive to use for this repair. I'm sure there are many others that are suitable, but when I saw the JB Weld was used to repair a tractor engine, well that ended my search. Here are the tools I used for this repair.
The repair process is simple... Mix up some JB Weld (you don't need much, but don't be stingy because the larger the glob of filler, the easier it is to get an equal part of the hardner).
Now you want to get that epoxy into the "moat" between the inner ring and the outer ring of the knob. And by all means, stay away from the set screw! I used a flat toothpick and a resistor lead to do this step. A syringe would be great, but I had to settle for the "low-tech" tools.
Clean off any epoxy that isn't where it's supposed to be, and let it cure. Give it 24hr to be safe. Then put the knob back on the rig, and you're in business. My repairs have lasted since mid-2006 without failure, so I think it's a pretty good solution.
If you have any questions or have additional information that I can add to this process, please contact me.
Tnx es 73,
ed - k9ew