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Thread: A quick question about dado bottoms

  1. #1

    A quick question about dado bottoms

    I'm far from perfect at cutting dadoes by hand, and I find that I often have uneven dado bottoms (e.g., the occasional divot/deep spot). My understanding is that the most important surfaces for joinery are the edges of the dado, not the bottom - as long as I am getting a good fit on the edges, how important is a perfectly flat/smooth dado bottom?

  2. #2
    Join Date
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    Hi Tyler

    Perfectly smooth is unnecessary Even perfectly flat is not important. But perfectly coplanar is vital and at the appropriate height to fit the piece.

    Having stated this, it is really a straight forward process with a saw, chisel, and router plane, or a dado plane.





    Regards from Perth

    Derek

  3. #3
    Join Date
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    Quote Originally Posted by Derek Cohen View Post
    Perfectly smooth is unnecessary Even perfectly flat is not important. But perfectly coplanar is vital and at the appropriate height to fit the piece.
    That is the biggest problem for me since I do not yet own the correct plane. It is on my list of things that I want to own. :-)

  4. #4
    Quote Originally Posted by Derek Cohen View Post
    Hi Tyler

    Perfectly smooth is unnecessary Even perfectly flat is not important. But perfectly coplanar is vital and at the appropriate height to fit the piece.

    Having stated this, it is really a straight forward process with a saw, chisel, and router plane, or a dado plane.
    Coplanar with the faces of the boards in which the dadoes are cut, I assume?

    My difficulties are primarily in stopped dadoes, as I have been chiseling the walls rather than sawing - I have difficulty sawing those adequately. On my next project, I plan to chisel out a small area at the end of the dado to let the saw travel freely to cut the rest. (Making a dado plane is also on my lengthy to-do list.)
    Thanks,
    Tyler

  5. #5
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    Quote Originally Posted by Tyler Bancroft View Post
    Coplanar with the faces of the boards in which the dadoes are cut, I assume?

    My difficulties are primarily in stopped dadoes, as I have been chiseling the walls rather than sawing - I have difficulty sawing those adequately. On my next project, I plan to chisel out a small area at the end of the dado to let the saw travel freely to cut the rest. (Making a dado plane is also on my lengthy to-do list.)
    Thanks,
    Tyler
    All the high spots on the floor of the dado need to be on the same plane. Some tear out below that surface will not matter.

    Depending on where you live it might be easy to find a used dado plane at a reasonable price.

    One of my recent finds was a Stanley #39 - 3/4":

    https://sawmillcreek.org/showthread.php?278928

    This was a experiment to make a stopped dado.

    It is fairly easy to make a dado with a saw and chisel:

    https://sawmillcreek.org/showthread.php?208154

    Before sawing a space is cut with a chisel at the stopped end of the dado for the sawdust to collect.

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

  6. #6
    Coplanar is not used correctly. Something needs to be coplanar with something else. Like you can't be a co-conspirator without a partner. And the bottom of a dado is not coplanar with the surface of the face of the board; they are in different planes. Perhaps he meant flat.

    Whether one is making a dado with a chisel, saw, or dado plane, the bottom is not particularly smooth, nor does it need to be. We usually use dadoes in conjunction with other joinery (like dovetails), so that they are not the only thing holding the piece together.

  7. #7
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  8. #8
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    A router plane is a wonderful tool & one that is below the radar of many woodworkers. I inherited one from my Dad & putting it to use has been a real eye opener. With dados cut on a table saw, I always run the router plane down them to make sure the depth is consistent because you never know when the board has lifted off the table a tiny bit. They are also great for fine tuning a tenon cheek because it will ensure that it stays parallel with the face of the board.

  9. #9
    Quote Originally Posted by Derek Cohen View Post
    Hi Tyler

    Perfectly smooth is unnecessary Even perfectly flat is not important. But perfectly coplanar is vital and at the appropriate height to fit the piece.

    Having stated this, it is really a straight forward process with a saw, chisel, and router plane, or a dado plane.



    Regards from Perth

    Derek
    I never knew a plane like that existed. Thats absolutely gorgeous. I will keep that on my list of things I would like to have but it looks like yours is very high quality and finding one like that may be hard and/or very expensive.

  10. #10
    Join Date
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    If you're not using a stopped dado, make sure you don't blow out the bottom at the front of the cabinet. It'll show unless a moulding will cover the edge. Sometimes the grain cuts better with the tool exiting at the front, but it's pretty much standard procedure to cut from the edge inward toward the middle of the dado if the grain will allow it. At any rate, as you're sinking the dado you'll get plenty of feedback on how the grain is running before you make your last few passes on the floor of the joint.
    Last edited by Charles Guest; 02-27-2020 at 11:01 AM.

  11. You can make a wooden Old Womans Tooth plane with a block of wood , wedge and chisel.

    Even simpler is a bit of hardwood with a nail knocked through, this will check depth.

    Best wishes,
    David

  12. #12
    Join Date
    Feb 2004
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    As David mentions, you can make your own.

    There are plans and a pictorial on my website: http://www.inthewoodshop.com/ShopMad...uterPlane.html



    I made a lot if these at one time.



    Regards from Perth

    Derek

  13. #13
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    I seem to recall a Paul Sellars video where he shows how to make some very simple but effective router planes.

  14. #14
    Join Date
    Jun 2010
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    twomiles from the "peak of Ohio
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    Like these?
    2 drawer chest, router work.JPG
    Had to slim things down a bit...
    2 drawer chest, B&B Tongue.JPG
    So the bread boards could fit..
    2 drawer chest, dry fit bread boards.JPG
    Panel is for a lid, and is only 5/16" thick....if that much.

  15. #15
    Quote Originally Posted by Derek Cohen View Post
    As David mentions, you can make your own.

    There are plans and a pictorial on my website: http://www.inthewoodshop.com/ShopMad...uterPlane.html
    I recently made one of these router planes from Derek's instructions and it works very nicely. Thank you, Derek!

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