I would take a drill bit about 2/3 the size of the hole, and mount it in a pin vise? an old, left-over drill chuck? For future reference, you can buy little chucks designed to convert from hex bits to a chuck, like under $10 on Ebay. Very, very handy to hold things. Better stronger chunkier than any pin vise. And then you just treat it like a reamer on the knobs, Keep the sides of the hole as parallel as you can.
In the mean time you could use that actual drill bit to drill through something/anything, just to hang onto it. A wood "bit" handle.. cram it into a BiC pen...? etc. just SOMEthing that lets you apply some brute force. if the metal in the knob proves to be too hard to make much progress, you can file the pot shaft it's elf. BUT - you DON'T want any shrapnel getting in the pot - curtains, my dear... And if it's already mounted and wired in such a way that you can't take it out to work on, shrapnel on the guitar finish = YIKES!!! You go to the kitchen, snag the roll of plastic film, pull out a piece long enough to cover the whole front (under these circumstances, Saran wrap is CHEAP compared to the agony of scratches you know dang well you could've avoided. :sad1: )
You just poke the one shaft you're working on through the film. In fact, if you're saving any beater towels or T-shirts and such as shop rags, you could poke that hole through one of them too). And then file away, always check berry berry* often often. Regularly, too. If you look at the splines and see how very little material you have to remove, I mean maybe 10 or 15 swipes with a #2-toothed metal file or the same amount with some 320 grit sandpaper wrapped around a popsicle stick may be TOO much. I don't really like bending them because the knob may get crooked and there's nowhere to go with that... in fact if I'm putting the wrong knob on the wrong shaft (no big deal, IMO) I'd put a little spacer in the slot of the shaft to keep it from bending.
Hmmm, a popsicle stick looks about the right thickness... :hello2:
http://www.youtube.com/watch?v=1U_hRhImaBU
