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Thread: tenon mistake

  1. #1
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    tenon mistake

    Started making 4 dining chairs, and in cutting the side stretchers I made the mistake of cutting the tenons in my cast iron tenon jig with a square cut instead of an angle of 5 degrees to match the offset from back to front. So what happened is in cutting all the pieces on one side cheek , I then put a sacrificial board in the jig and cut the inside cheek. When I put it together, I get this on one side
    20190819_100733.jpg

    but the other side, of course, looks like this
    20190819_100759.jpg

    I could plane them all but my skill (or lack there of) will I'm afraid result in 16 custom fit pieces to keep track of.

    So I'm thinking that I'll cut the correct angle on the existing tenon and then re-cut all the pieces (somewhere near the red line). I'll loose about a 1/4" +/- but that's ok. Any other suggestions?
    2019-08-19_13h09_26.jpg

    But at least I got to use my garage sales find on the curved legs. So that's somethin.
    20190813_105615.jpg
    If you don't stand for something, you'll fall for anything.

  2. #2
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    Roy Underhill once demonstrated a trick for this kind of mismatch of tenon shoulders. With the joint held closed, he used a saw on the side of the joint opposite the gap. This effectively trimmed the shoulder to close the gap. You may want to use a saw with zero set.

    jtk
    Last edited by Jim Koepke; 08-19-2019 at 2:46 PM. Reason: changed wording for clarity
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  3. #3
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    Nice idea Jim. I'll try it with a mortised sacrificial piece. Thx.
    If you don't stand for something, you'll fall for anything.

  4. #4
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    That gap is pretty close, already. I would be inclined to assemble each piece on it's designated leg with a captured piece of fine "plumber's tape" facing the proud shoulder. Draw the tape through with light pressure holding the leg in the mortice.

    Even the finest flush cut saw is about .5mm thick.

  5. #5
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    Quote Originally Posted by Jim Matthews View Post
    That gap is pretty close, already. I would be inclined to assemble each piece on it's designated leg with a captured piece of fine "plumber's tape" facing the proud shoulder. Draw the tape through with light pressure holding the leg in the mortice.

    Even the finest flush cut saw is about .5mm thick.
    Took me a bit to figure out what you were suggesting Jim - plumber's tape to me is the Teflon tape used on joints. But I think what you're proposing is to use the emery cloth sandpaper used to prep pvc piping, yes? Sand the shoulder to fit - which will be easier if I back pare the shoulder first. Worth a try. Thx.
    If you don't stand for something, you'll fall for anything.

  6. #6
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    Sorry I wasn't clear a out that.

    You got the gist.
    Since the joint will "show" sneaking up on it requires caution.

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    plumber's tape to me is the Teflon tape used on joints.
    My memory of plumber's tape is influenced by being around a few who worked in the trade during the 1950s. This was when a stick of pipe dope was used on the joints and plumber's tape was a roll of metal strap with holes every inch or so. It was often seen holding pipe on joists among other uses.

    A roll of plumber's tape and a roll of friction tape were the ducttape of the ERA.

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

  8. #8
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    Quote Originally Posted by Jim Koepke View Post
    My memory of plumber's tape is influenced by being around a few who worked in the trade during the 1950s. This was when a stick of pipe dope was used on the joints and plumber's tape was a roll of metal strap with holes every inch or so. It was often seen holding pipe on joists among other uses.

    A roll of plumber's tape and a roll of friction tape were the ducttape of the ERA.

    jtk
    Yes they were. I remember holding parts of my first orange crate cart together with plumbers strap. And friction tape on my baseball bat was the cats pajamas.

    But this chair project has gone completely off the rails. I made adjustments to the shoulders so they fit and assembled the back and sides of one chair and noticed that the side stretchers were not at the same angle to the back. The upper was at 5 degrees and the bottom on the same side was at about 3 degrees. I checked the tenons and they lined up, so for the hell of it I milled a straight piece with a perfect tenon and put it in the top mortise, then the bottom mortise, and they were different. Over to the mortise machine, and when I tightened a piece on the table, I found that the back fence - or the angle block as they call it - was loose. So when tightened, it was not at 90 degrees, but maybe 4 or 5 degrees past 90, which meant that all my mortises were suspect. So I fixed that - after a helpful call to Baleigh - and now will re-mortise the legs for 1/2" tenons instead of 3/8, and I'll remake all 16 stretchers.

    And so it goes.
    If you don't stand for something, you'll fall for anything.

  9. #9
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    No need to remake all the stretchers.

    Glue on shims to fit the new mortice width (presuming the tenons align.

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    Quote Originally Posted by Jim Matthews View Post
    No need to remake all the stretchers.

    Glue on shims to fit the new mortice width (presuming the tenons align.
    Thanks Jim (and Jim) gluing shims on and sanding the shoulders have put the chair project back on track.
    If you don't stand for something, you'll fall for anything.

  11. #11
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    One of my suggestions helped?

    First time for everything, I suppose.
    Good onya to finish the project - no one can take that from you.

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    Join the throngs of WWers who make mistakes!!!!
    Jerry

  13. #13
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    Quote Originally Posted by Jim Koepke View Post
    Roy Underhill once demonstrated a trick for this kind of mismatch of tenon shoulders. With the joint held closed, he used a saw on the side of the joint opposite the gap. This effectively trimmed the shoulder to close the gap. You may want to use a saw with zero set.

    jtk
    Jim, not to derail the O/P, just wanted to comment that I appreciate the fact that you very frequently attribute knowledge you pass along to where you got it from. In this day and age I think thatís getting a little rarer. Thank you.

  14. #14
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    Quote Originally Posted by Jim Matthews View Post
    One of my suggestions helped?

    First time for everything, I suppose.
    Good onya to finish the project - no one can take that from you.
    yes, your suggestion helped. I liked the simplicity of it: glue on shims. Done. Perfect. Thanks.
    Here's what it looks like this am:
    20190823_182743.jpg can never have enough clamps.
    If you don't stand for something, you'll fall for anything.

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    Quote Originally Posted by Kurtis Johnson View Post
    Jim, not to derail the O/P, just wanted to comment that I appreciate the fact that you very frequently attribute knowledge you pass along to where you got it from. In this day and age I think thatís getting a little rarer. Thank you.
    Thanks for the kind words Kurtis. It is a way of letting people know there are many sources of knowledge from which they can draw. It also lets folks know there is a vast amount of knowledge to be learned without a lot of time consuming trial and error.

    Most of my knowledge comes from observing others, reading from many sources and finally from refining what others have done before by way of my own endeavors.

    There is more rediscovery of old or forgotten methods than there are actual creations of new ways to work wood. Surely many years ago even Roy Underhill had someone teaching him. His teacher was likely mentored by another skilled person during their early days of working with wood.

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

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