Drilling Through a Finished Top.

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by humbert, Jul 17, 2008.

  1. humbert

    humbert Member

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    Hi-

    I just bought a guitar, and the holes in the top for the pots aren't wide enough to accomodate my spst switch and DPDT push-pull pot.

    I'd like to drill through the top to get those components in there--however, I've never done anything like that to a guitar, just pedals. I've got a Uni-bit and a standard electric drill.

    I'm worried that piercing the top to widen the hole might cause the finish around the mounting hole to crack.

    Should I be worried? Is there a trick to this, or can you only do it when the guitar is unfinished?

    It's not an expensive guitar, and I don't mind if mine get beat up, but I would like to make sure I don't cause structural damage or huge finish chips or cracks on the top.

    Thanks a lot,

    Tim
     
  2. Rosewood

    Rosewood Member

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    If the unibit is the right size, will center itself, and you go slow and keep the bit straight you shouldn't have a problem. Some people use masking tape over the hole to keep from chipping, I never do.
     
  3. mike80

    mike80 Member

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    Try running the unibit in reverse to lessen the chances of splitting/chipping. Once you get through the finish that way, then you can put it in forward gear and proceed.

    I tend to dislike unibits for precision drilling because of the taper on them. Some are tapered so much that you think you have the right size (and you may on the top), but the part won't fit though the bottom, and you need to go another step. Sometimes that leads to parts not fitting right on top. Just IMO.
     
  4. TimmyP

    TimmyP Member

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    If that is the case, you need a UniBit with longer steps. You can also drill halfway through from each side.
     
  5. mike80

    mike80 Member

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    That's true. My experience with Unibits is mainly in construction, and sometimes you can't get a drill in on both sides. That leads to conduit connectors not fitting squarely, etc.

    They definately have a use, and I own several of them, I would just rather use a regular drill bit in most cases.
     
  6. humbert

    humbert Member

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    This DeArmond has a really thin top over the control cavity. So thin I don't even need long-shaft pots.

    Thanks,

    TN
     
  7. Mike9

    Mike9 Supporting Member

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    You can chuck in a standard bit of the correct size and run the drill BACKWARDS - it will be pretty much self centering
     
  8. Jack Briggs

    Jack Briggs Member

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    This is my recommendation also. Chipping of the finish is the main concern with drilling using a twist-type drill bit, but reversing it will alleviate that concern.
     
  9. Quarter

    Quarter Member

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    Starting the hole in reverse to minimize chipping and tear out is great advice for finished or raw.

    For reaming a larger hole, I tend to prefer the step bits as they have more surface area on the face / taper of the cutting edge. Larger twist bits can wobble and make a mess if not properly chucked up in a press.
     
  10. Mike9

    Mike9 Supporting Member

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    Not starting the hole in reverse - go all the way through in reverse. A fresh bit will cut just fine in reverse - never, ever use a twist drill in forward on a peg head, or body especially with finish on it and especially at slow speed. Once the material catches the cutting helix it's all over but the cryin' . . . . and the swearin' . . . ;)
     
  11. Bob V

    Bob V Member

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    Assuming the body is deep enough or there's a control plate opening on the back, then you're safest with a handheld tapered reamer.
     

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