Knob spline repair

paulnb57

On my 40 year old Yamaha Lord Player the spline inside one of the tone knobs has worn away over the years in previous ownership, is there way to reinstate the spline to keep it original?

ICBM

Tricky...

I think I would use a very small amount of quick-set epoxy, the stuff that goes rubbery before it sets hard. Coat the inside of the hole (sides only if you can) with enough to make up the missing amount of plastic, then using some left-over epoxy as a reference, wait until it's got to the point of being rubbery and not very sticky any more, press a spare pot with the right number of splines into it. You *should* then be able to get the pot shaft out again after it's hardened if you've timed it right so it doesn't stick to the metal.

NB - I've never done that on a guitar knob, but I have on an old bakelite door handle, and it did work.

paulnb57

Thanks @ICBM worth a try

BillDL

I've done this a few times using clear 2-part epoxy as ICBM has suggested.  If you coat the splines of an old pot with a fine smear of vaseline it should pull back out again without disturbing the setting glue if you time it right. I practiced before committing using an old knob that I deliberately bored out to ruin the internal splines.

Another bodge I've done is to find some metal sheet that's thick enough to push into the slot of the pot and cut a rectangle that's the same length but marginally wider than the splined section. Gently compress the split sections to hold the piece of metal in the slot and then push the knob onto the pot so that the sticking out bits of metal cut new key slots into the inside of the plastic of the knob.  You can still get the knob back off if you need, but you have to carefully line it up again when pushing it back on.

paulnb57

Thanks @BillDL ;