How to increase the inner diameter of a plastic knob

[Mincer]

Re: How to increase the inner diameter of a plastic knob

Or, bit in a vise and slowly spin the knob by hand.

[GuitarDoc]

Re: How to increase the inner diameter of a plastic knob

I just did this with a stepper a few weeks ago. -On the GK style plastic knobs that have the gray cap so the stepper easily widened the channel and protruded out the other side with the gray cap off.

Second, you can absolutely do this with 32nd or 64th bits . -I used to this in my sleep as a kid when adding weird knobs to solid posts.. I think the difference here is Guitar Doc is giving you the more correct Luthier approach, I was giving you the home solution because as indicated I said I'm guessing you are going old school without specialty tools.

Well, of course a step drill will work on a hollow cylinder!!! (And that's effectively what you have if you are working on a knob that has a removable cap). But I don't think that's what we have here.

The suggestions that I gave, or the ones about doing it by hand are the most appropriate.

[GuitarDoc]

Re: How to increase the inner diameter of a plastic knob

Or, bit in a vise and slowly spin the knob by hand.

Yes, this is the best way to do it if the "correct" tools aren't available.

[ItsaBass]

Re: How to increase the inner diameter of a plastic knob

I would start the hole with a hand reamer, going as far as you can that way. Then finish it off with a drill (drill press, if you have one). The reamer helps to ensure that your hole doesn't drift off center.

[GuitarDoc]

Re: How to increase the inner diameter of a plastic knob

The hole won't drift if you use conventional drill bits progressively wider in tiny increments. Certainly it can if you go right to the final size.

That's NOT to say that using a reamer is NOT a good idea, but it is actually pretty easy to get the opening of the hole too wide using a reamer by hand.

[Jack_TriPpEr]

Re: How to increase the inner diameter of a plastic knob

BTW, I will be working with these two knobs - the Fender Jazz Deluxe Stacked Concentric knobs - PN 004-9411-000. The top piece ID is 3/16" (0.1875") and the bottom piece ID is 1/4". I need to increase the top piece ID to fit a 6mm (0.236") pot shaft, and the bottom piece ID to fit a 8mm (0.315") pot shaft.

Based on all the helpful replies so far, it seems i will be fine if i take it slow, take it in increments, and do as much by hand vs electric to start with. Thanks!

[GuitarDoc]

Re: How to increase the inner diameter of a plastic knob

^ +1