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Drilling Without Chipping

Discussion in 'Luthier's Corner' started by Saint, Apr 11, 2004.


  1. Saint

    Saint

    Mar 2, 2000
    DC - USA
    I am about to drill control cavity holes in my carved-top bass body. I've always drilled from the inside of the cavity out to the front of the bass before and that has worked fine.

    The problem in this instance is that, because it is a carved top, it will not lie flat on a backing board and I'm affraid that when I drill, there will be a great deal of chipping of my AAA Flame Maple top.

    Can anyone offer advice on how to properly drill in this situation?

    Thanks in advance for your help.
     
  2. Skorzen

    Skorzen

    Mar 15, 2002
    Springfield MA
    Here are a couple ideas I had. Please take these with a grain of salt because I have not personally done exactly what you are doing. My first thought was to use a piece of rolled up cardboard or something that will fit the radius of the top and use that as a backing piece, but that might not totally eliminate the problem. My next thought was to use a small drill from the back to create a pilot hole and then use the regular sized drill from the front. If you wanted to get really fancy you could drill the pilot hole and then drill most of the way though from the front, and then flip it over and drill from the back. That should elinate all chipping. Be sure to use as sharp a drill as possable.
     
  3. JPJ

    JPJ

    Apr 21, 2001
    Chicago, IL
    Whenever chipping or splintering is an issue, it's always a good idea to score the surface that you're working on. Like above, I can't offer first-hand experience as I've never tried what you're looking to do, but using a box cutter or other thin, sharp blade, you should be able to score the surface and make a deep cut along the outer rim of the area you're woking in that should minimize any chipping or splintering. Good luck with the project.
     
  4. The answer to all your problems!
    put a piece of scrap on each side, drilling through all 3 peices. This will keep any splintering or spliting from occuring. Just ask Norm Abram from the New yankee workshop, it's what he'd tell ya to do ;)
    Peace :smug:
     
  5. Skips

    Skips

    Feb 19, 2003
    I tried this for tuning holes on a headstock a while ago. The headstock cracked in half when I drilled the bigger hole. :bawl:
    That was the last time I ever used a hand drill for anything. I got a drill press right away and used the larger size first, and did all the other holes without problem. I asked on MIMF if they thought the problem was the the fact that I was using a handdrill, or that I was enlarging the hole, or that I was using very brittle Ironwood.
    They said it was probably a combination of them all, but recommended using a round file to enlarge a hole rather than drilling bigger to prevent chipping.
     
  6. Skorzen

    Skorzen

    Mar 15, 2002
    Springfield MA
    I can see that happening, but what I had in mind was using something like a 1/16" or smaller bit, I don't think you would have a problem, but make sure it is sharp, and go slow.
     
  7. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    In drilling holes have used all of these and they work. Back side is usually the main problem area. The Yankee workshop thing does work well. You can practice on something else to see what procedure you feel comfortable with. In drilling additional potholes through the face of hard finishes I've laid down masking tape and just drilled through it to keep the finish from cracking. Sharp bits, high speed, go slow - and cross fingers.
     
  8. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    He already said that he can't do this because the top's curved.
     
  9. Oh NO! my nightmare is a reality where all the pieces of scrap have become permenantly flat!!! jk ;)

    I'm sure with a little engineering this wouldn't be terribly hard. Try it, if it doesn't work out to use a pliable or shaped scrap, then don't do it. I'm betting you can do it though. :smug:
     
  10. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    If the area where the shaft comes through is significantly curved, how do you intend to to put the top nut on and tighten it? Are you going to spotface it (and run into the same problem all over again)?
     
  11. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Ballpean to washer (joking). Good point actually, but it'd have to be some serious curvative to pose a problem I'd think.
     
  12. pkr2

    pkr2

    Apr 28, 2000
    coastal N.C.
    I believe you are greatly underestimating the problem of trying to keep a pot tight if there is any curvature at all where the nut tightens down.
     
  13. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Quite possibly. I've as yet to have such an occassion. But it wouldn't be the first or last time an outcome was other than I expected. But if that's the case, then you probably would want to avoid designing that into the instrument if at all possible or experiment with a fix that you know works before hand. But it sure doesn't sound like an insurmountable task on the surface (no pun intended - in this case anyway).
     
  14. Well, drill press and high speed has been said already. it also depends somewhat on the type of bit you have or plan to use.

    for larger holes there are bits around (forstners come to mind) which will self-score and greatly redice chipping. I don't think they're sold in sizes smaller than 3/8 or so.

    Some brad point bits will also reduce chipping as they have side spurs to score the outline of the hole.

    finally, even if you can't rest the entire unit on your table due to curvature, chances are that you can sand a small block (2x2 is fine) to match the curvature of the area and tape it on securely. With the added pressure of your bass (or your hand or a clamp; i'm having trouble imagining exactly how you'd hold it) it should also help to reduce chipping.
     
  15. Tim__x

    Tim__x

    Aug 13, 2002
    Alberta, Canada
    I've never tried, but would a small rubber washer in between the nut and the body work?
     
  16. Suburban

    Suburban

    Jan 15, 2001
    lower mid Sweden
    A normal pot thread hole would be, like, 7mm.
    If you drill a pilot from inside, diameter 2mm, you can use any kind of drill to enlargen it, from the outside. The risk of breakage, in this area, is diminuitive, at the most.
     
  17. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    Maybe a thin rubber washer, and then loktite on the nut.

    That gave me an idea - A sacrificial piece of rubber on the curved side when drilling might work to prevent the chipping. I had been thinking of building up a wad of masking tape.



    In any case, if you did produce a chip, it would have to be very large in order to not be covered by the knob.
     
  18. Saint

    Saint

    Mar 2, 2000
    DC - USA
    Thanks everyone for all the helpful feedback.

    I may try a very narrow pilot hole for each drilling back to front, then drill the main hole from front to back.

    I hadn't thought about the problems with uniformity re: control pot mounting, but I will start thinking about it now.
     
  19. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Drilling a pilot hole should tell you something about the potential for something large to chunk it up. I'd get a magnifying glass in broad daylight and see how uniform the hole is. If it looks real clean, at least I'd feel more comfortable. Another thing I'd consider is drilling for a small diameter pot. If it does chunk it a little, it may cover with the washer or at least you'd have a second go at it if you chose to for a larger pot size. Just a thought.
     
  20. nybass6

    nybass6

    Feb 14, 2008
    I'VE USED A RUBBER SANDING BELT CLEANER (BIG ERASER) TO SUPPORT THIS TYPE OF DRILLING . IT WILL FOLLOW THE CONTOUR IF YOU APPLY ENOUGH PRESSURE AND THE RUBBER IS THIN ENOUGH (1" OR SO). HOWEVER , I FIND THE BEST RESULT, IS TO PLAN AHEAD AND DRILL BEFORE YOU CARVE . I DO THE SAME FOR BODY ROUTS AND HEADSTOCK DRILLING .