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Thread: Dumb drilling question

  1. #1
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    Dumb drilling question

    This question is really basic, and I would be embarrassed to ask it anywhere else, but here goes.

    I'm making a jig, mostly out of 3/4 mdf. Two plates are held together by nuts and bolts. I want to bury the head of the bolt in the mdf so it will be flush, but as its mdf, I don't want to cut out more stock than necessary.

    So stated in a general way, I need two holes, a 1/4 thru hole for the shank of the bolt and a 1/8th deep and 7/16 wide hole to bury the head, basically a small hole centered in a bigger shallower one.

    I have some countersink/counterbore bits (never exactly the right size of course ) and a good selection of twist bits and forstner bits.

    I tried a couple this morning, just eyeballing putting a 1/2 inch forstner over the 1/4 hole, and did a pretty awful job.

    Tell me there's a silver bullet!!

  2. #2
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    It is probably to late, but I find the easiest way for me to do that sort of thing is to drill with a forstner bit first so that it will stay centered and then drill the smaller hole. both should be centered and have clean cuts. If you are going to use a counter sink bit, dirll a very small hole first and then countersink, then enlarge the smaller hole with a correct size larger bit. This is assuming that you do not have the correct combination of bit/countersink.

    Good luck! Allen
    Last edited by Allen Bookout; 01-17-2007 at 06:50 PM.

  3. #3
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    Jessie,
    are you drilling with a drill press or hand drill?

  4. #4
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    Quote Originally Posted by Frank Chaffee View Post
    Jessie,
    are you drilling with a drill press or hand drill?
    Drill press.

  5. #5
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    Big first, then small through center of biggie.

  6. #6
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    I'll fourth the 'big first, small second' suggestion. The point of the bigger forstner bit will leave a hole from which to start the smaller bit. If for some reason you have to drill the small hole first, then I'd suggest clamping the piece to the drill press table before the small hole, and not moving it when you change bits to do the big hole. As long as nothing moves, the big bit should still be centered on the hole.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
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  7. #7
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    yup......big then small.
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  8. #8
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    Forstner, then the hole, like the others said. I do this when countersinking t-nuts. Jim.
    Coolmeadow Setters...
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  9. #9
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    when you make the mistake of drilling small first, countersink the small hole till the forstner bit will just fit inside the countersunk park and then counter bore it, the countersink part will center the forstner bit.
    Drawknife, Spokeshave, Plane, Rasp; Decisions, decisions.
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  10. #10
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    when you do mess up and drill the small hole first take a piece of mdf and drill all the way through then center it over your small hole, clamp in place and use as a guide for the forstner...tod
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

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