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Thread: Specific ebony headstock overlay tearout problem

  1. #1
    aka "Hydrilla" Darren Kern's Avatar
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    I had very bad tear-out from drilling tuner holes on my #1, and I want to prevent a repeat performance with the mandos I'm at that stage with now. I thought I did things correctly- since it was a kit that had tuner holes already drilled through the headstock, I clamped it face down onto a board, and drilled from the back, starting with my smallest drill bit and going up to the final one, without skipping any inbetween. Since I had it clamped well, I didn't stop to check for tearout inbetween bits. The only thing I could think of is that the board I clamped it to was spruce, and that it was too soft to prevent tearout, but that doesn't really make sense to me. The 3 mandos I'm getting ready to drill now are all kits as well, with the tuner holes already drilled in the headstock but not the overlay. I thought about cutting out a piece of hardwood close to the headstock shape and clamping them to that, do you think that would help? I can't think of anything that I've left out, other than the drill I'm using is a 15 volt cordless (don't have a drill press yet). Thanks.
    My original IV mandolin kit blog- http://makingamandolin.blogspot.com/

  2. #2

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    Darren,
    Clamp a piece of maple to the face of the peghead. Use a brad point bit of the correct size...don't drill with increasing size bits. That will get you there without tearout. I use a cordless drill, but have a drill guide made of aluminum with steel inserts.

  3. #3
    aka "Hydrilla" Darren Kern's Avatar
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    Thanks Hans, I don't own any brad point bits, but I'll go buy at least the one I need for now. The bit I used last time made for a REALLY tight fit with the Schallers tuner bushings I used, too tight really. I now have a violin peghead reamer that I figured I could use to gently expand the holes very slightly if this happens again.
    My original IV mandolin kit blog- http://makingamandolin.blogspot.com/

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    Darren,
    When drilling wood with conventional drill bits, you should grind the positive rake off the cutting edges of the drill bit. That with the back up board of maple will give you a virtually perfect hole...gavin

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    Even though I have the special drill bits, I have just been putting a backing piece of wood on the drill press and using a standard twist drill from the back side of the head and haven't ever had one rip out the front. I use the same size drill as the tuner hole (which I have already drilled in the head prior to gluing on the ebony also with a backing board.) Maybe I have just been lucky ?
    Bill P.
    I am a nobody, and nobody is perfect; therefore I am perfect.

  6. #6
    aka "Hydrilla" Darren Kern's Avatar
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    Thanks Gavin, I had to get one an engineer buddy here at work to show me what you were talking about, but now that makes total sense. Lots to learn.
    My original IV mandolin kit blog- http://makingamandolin.blogspot.com/

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