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Thread: Glue and joints freezing up before fully seated(!)

  1. #1
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    Glue and joints freezing up before fully seated(!)

    I wanted to write up a quick post on something that nearly ruined a leg assembly I was working on!

    As some of you may be aware, I'm building a small Sloyd style bench. For the leg assembly, I'm using through mortise and tenons at the top and bottom of each pair of legs.

    The tenons fit snugly in place -- not so tightly that they require heavy pounding to remove, but not so loosely that you can just pull it apart with little effort. This is about the fit that I usually aim for.

    However, once I went to glue and assemble them, the joints became impossibly tight fitting. I do not know if the glue thinned out and began to dry very quickly (it seems that white wood glue can do this, drying very quickly when thinned down) or if it just wet and swelled the wood, but my tenons became impossibly stuck about 3/4 of the way seated, with a large gap. I could not pound or press them in, nor could I pull or pound them apart. Totally stuck.

    Fortunately, I am a 10 minute walk from the nearest home center, where I bought some very long and sturdy F clamps. I put a bunch of those on and tightened them down -- at first, and for a while, the joint still did not move, but after about 15 minutes, just as I was rushing to the internet for advise on how to disassemble a glued mortise and tenon, I noticed that they had slid down into place.

    The remaining mortise and tenons I've glued with some slow drying Titebond hide glue, and have had no problem. It seems that the hide glue does not increase friction or swell the wood or "freeze up" the joint like white wood glue can do, plus it gives me extra time to work and can be more easily unglued if necessary.

    Is this something that any of you have had to deal with? Are my observations consistent with your own?

  2. #2
    If you partially assembled the joints with white glue then pulled them home after another half hour the glue bond is likely not strong at all. Pin them if you can. Most pva glues are designed to tack up quickly, so you need to have your clamps and blocks ready and work expeditiously. A dry run is never wasted time. Titebond Extend will give some extra assembly time, while liquid hide glue, epoxy and plastic resin (urea formaldehyde) will allow for relatively lengthy glueups.

  3. #3
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    Quote Originally Posted by Kevin Jenness View Post
    If you partially assembled the joints with white glue then pulled them home after another half hour the glue bond is likely not strong at all. Pin them if you can. Most pva glues are designed to tack up quickly, so you need to have your clamps and blocks ready and work expeditiously. A dry run is never wasted time. Titebond Extend will give some extra assembly time, while liquid hide glue, epoxy and plastic resin (urea formaldehyde) will allow for relatively lengthy glueups.

    Thanks! I was also thinking that the glue may not be as strong as usual. There was squeeze out of very liquid glue when the joint did finally slip into place, so it may surprisingly strong after all, but putting a pin in for reinforcement can't hurt.

    That said, there is unlikely to be any significant stress on the joint that would cause it to come out. It was tight to begin with, and a complete through mortise -- moreover, the bench top will be resting on top of it and pressing it down into place. It would likely function just fine even if never glued at all, and I fail to see how anything catastrophic would happen if it does come unglued -- I'd just glue it again.

    I wonder what the cause of the seizing up actually was, though. Was it due to the glue drying, or the glue wetting and expanding the wood, or just the volume of glue creating far more resistance than I anticipated, and being difficult to squeeze out?

    In any case, I've learned something! From here on I'll be sure to have clamps on hand just in case body weight and a mallet are not enough to close up a joint.... And also opt for a slow drying glue where any chance of trouble exists.

  4. #4
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    Most likely the glue caused the wood to swell.

    One author on mortise and tenon joinery suggests one should be able to drive a tenon in with a hat.

    That seems a little loose to me. Though many of my mortise and tenon joints are not glued. Instead they are draw bored. These will be likely much easier to disassemble if needed than an M&T that is glued.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
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  5. #5
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    Used to be...they said to wrap the tenon with a dollar bill, THEN try to insert into a mortise.....thickness of the paper in a dollar bill is....?



    From no less an "Authority" than FWW.....back in the early 1990s....

    Not only to allow room FOR the glue.....also to allow air to escape from inside the joint. "Piston Fit...sometimes results in a Vapor-lock.....where the air can't escape while the tenon is being inserted....hence the wrap of a dollar bill to check the fit.
    A Planer? I'm the Planer, and this is what I use

  6. #6
    Quote Originally Posted by Jim Koepke View Post

    One author on mortise and tenon joinery suggests one should be able to drive a tenon in with a hat.
    jtk
    I remember the saying as if you need a hammer to drive it home it's too tight, if your hat will do it's too loose.

  7. #7
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    A friend who is a hand tool woodworker sized all his mortise and tenon joints so when dry fitting he could press them together by hand and they made an audible pop when pulled apart
    Steve Jenkins, McKinney, TX. 469 742-9694
    Always use the word "impossible" with extreme caution

  8. #8
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    For the leg assembly, I'm using through mortise and tenons at the top and bottom of each pair of legs.
    Quote Originally Posted by steven c newman View Post
    Used to be...they said to wrap the tenon with a dollar bill, THEN try to insert into a mortise.....thickness of the paper in a dollar bill is....?

    From no less an "Authority" than FWW.....back in the early 1990s....

    Not only to allow room FOR the glue.....also to allow air to escape from inside the joint. "Piston Fit...sometimes results in a Vapor-lock.....where the air can't escape while the tenon is being inserted....hence the wrap of a dollar bill to check the fit.
    Vapor lock shouldn't be a problem with a through mortise.

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

  9. #9
    PVA Wood glue is water based and can quickly swell the tenon as soon as it's applied, making the fit too tight.
    This is not uncommon, you just need to work quickly once the glue has been applied to the tenon. In the future you can either make the fit a bit looser to begin with, like the dollar bill method mentioned or apply glue to the mortise first then just a quick brush of the tenon right before assembly.

  10. #10
    Usually I already know what kind of glue I'm going to use before I start cutting my joinery. If I'm using hot hide glue, I will shoot for making them as tight as possible because HHG actually lubricates the joints making them easier to go together. If I'm going to use white glue or some incarnation of a PVA, then I shoot for joints that are just a little loose.

  11. #11
    I agree with poster Chris Carter, hide glue lubricates a joint, so tight fitting joinery goes together like a dream.

  12. #12
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    Thanks guys! Great feedback!

    I'll start paying attention to which glue I use now when fitting joints. PVA for filling loose joinery, hide glue for tighter fits. That seems to be logical to me, anyway.

  13. #13
    Quote Originally Posted by Luke Dupont View Post
    Thanks guys! Great feedback!

    I'll start paying attention to which glue I use now when fitting joints. PVA for filling loose joinery, hide glue for tighter fits. That seems to be logical to me, anyway.
    If your joinery is loose, I'd use epoxy. PVA is not a good gap filling glue.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  14. #14
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    Also handy to have bigger hammers available. And some sacrificial pieces in the scrap bin when you need the bigger hammer.

    Less experience than most here, but if the dry fit was OK I would suspect the water in the glue causing your wood to swell at glue up, and a bigger hammer will overcome that within reasonable limits. And possible stacked errors.

    Not sure where the "real" cutoff is, but in Douglas Fir for tenons one inch thick and up (need a 1" chisel to cut the mortise) I look to the drawbore pin for primary fastening, tenon thickness up to one half inch thick I look to glue. I have read here some of the colonial era window frames in hardwoods back east in very small stock are drawbored with no glue like for the four pieces of frame around a piece of window glass.

    Part of it I think is scale and timing. If you are dropping live trees and cutting 2" mortises and tenons to build a barn and all your neighbors are coming over to raise the frame as soon as you are ready, "hat in a hallway" makes sense because the barn has to go together day of, it will keep moving after raising and draw bored pins work. If you got a bunch of acclimated stock for a china cabinet or a clock you can go pretty tight and lean on the glue for no pins showing on the finished surfaces. I don't mind the look of drawbored pins, and love they way they can pull joints tight, so there are both structural and aesthetic considerations.

    I used 1.5 inch tenons on my Doug Fir workbench. Two of the joints that fit just fine individually dry needed an 8# sledge to persuade them to go home at final assembly. I had stack fault in mine, where a little error here and a little error there added up to Mr. Persuader on the last two joints to go home - dry. I glued my pins in after dry assembly.

    Main thing from me is don't give up and keep walking the walk. Your next project will come out better if you keep learning from the last project.

  15. #15
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    Have you put glue on both tenon and mortise?

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