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Thread: Large mortises?

  1. #1
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    Large mortises?

    When cutting a large mortise - say 3/4" to 1" wide, do you use a brace and bit to hog out the bulk of the material or pure chisel? When using a brace and bit, is there much concern for the chisel twisting when going back to clean out the remaining waste? Any other words of wisdom?

  2. #2
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    I use a drill press and a forstener bit. Heresy for a Neanderthal perhaps, but more accurate than if I used a brace and bit.
    Sharp solves all manner of problems.

  3. #3
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    If they’re also long then I would much rather just chop them out.
    Bumbling forward into the unknown.

  4. #4
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    Usually just chisel them out....

  5. #5
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    Yep, just chisel them.

  6. #6
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    Mine have been done both ways. Overlap the drill bit a little and then you won't have as much twisting of the chisel since you will be paring away the Vs left between the bored holes.

    Roy Underhill does this on an episode called "Big Ash Mallet":

    http://www.pbs.org/video/big-ash-mallet-jn5sfd/

    He first chops a shallow mortice as a guide for the bit placement.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  7. #7
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    The really big ones (2"x6") I drill out first, then pare to the line. Can also drill a hole top & bottom, thread the bow saw and cut lines.
    ​You can do a lot with very little! You can do a little more with a lot!

  8. #8
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    Drilling before chisel work makes cutting a mortise quicker, but usually less precise, especially if you use a brace.

  9. #9
    One technique we sometimes use for a wider mortise is to make two narrow mortises, like 1/4 or 5/16, one on each edge, and then chop out the material in between. Depending on your skill with a mortise chisel, this could be faster or more precise.

  10. #10
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    Quote Originally Posted by Warren Mickley View Post
    One technique we sometimes use for a wider mortise is to make two narrow mortises, like 1/4 or 5/16, one on each edge, and then chop out the material in between. Depending on your skill with a mortise chisel, this could be faster or more precise.
    Good advice here. It's no fun beating a 1 inch mortise 5 inches long into a hickory bed post. Two 5/16 ones and a little clear out is much easier. I leave those big chisels to the timber framers.
    Jim

  11. Quote Originally Posted by James Pallas View Post
    Good advice here. It's no fun beating a 1 inch mortise 5 inches long into a hickory bed post. Two 5/16 ones and a little clear out is much easier. I leave those big chisels to the timber framers.
    Jim
    Kinda wonder at that point if just doing a dual mortise and tenon joint might not be a better call than a single one. Wish I was experienced enough to know off the top of my head

  12. #12
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    Quote Originally Posted by Daniel O'Connell View Post
    Kinda wonder at that point if just doing a dual mortise and tenon joint might not be a better call than a single one. Wish I was experienced enough to know off the top of my head
    Good point. Twin tenons make a much stronger joint in some ways than a single tenon. More glue area (not usually an issue in big tenons) and especially much more resistance to torsion (twisting). If the tenon is acting in tension (withdrawl forces) and secured with a pin, then effective cross-sectional area of twin tenons may be seen as less than a single tenon of the same cross sectional area in some conditions. It depends on the size of both members being joined and the forces involved.

    Cutting twin tenons precisely in large timbers takes superior skills in layout, saw-work, and chisel-work than for cutting a single tenon. Not something for the amateur to attempt in an actual timber frame without practice.

  13. #13
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    I usually get the bulk out by drilling and the rest with a chisel...
    Jerry

  14. #14
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    Loose Tenon? Make a mortise in both pieces and make a tenon to fit the two holes? The tenon can be glued to one or both pieces. Biscuits, dowels, dominoes are all loose tenons. You can make more or less loose tenons depending on the pieces being joined. Drawboring would be a variation of a loose tenon as well. A tenon or peg with the grain running the full length of the tenon is a stronger tenon and relatively easy to make.

  15. Quote Originally Posted by Stanley Covington View Post
    Cutting twin tenons precisely in large timbers takes superior skills in layout, saw-work, and chisel-work than for cutting a single tenon. Not something for the amateur to attempt in an actual timber frame without practice.

    At this point in the hobby I am having trouble enough getting single mortises chopped consistently. Acquiring a couple good mortise chisels has helped

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