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  • How loose should a dado be?

    Hello

    I'm making a cabinet that's assembled entirely using dados. I've cut them to be just a couple of hairs bigger than the planks, so that I can insert them without hammering, but they're not loose.

    Today I started gluing it, did just 4 of the dadoes. I used Titebond III, which I've never used before. I spread the glue with my finger - a very light coating on both sides. Then the problem. It was incredibly difficult to insert the pieces into the dadoes. I had to clamp them very hard and hammer them with a scary amount of force just to make sure they're in all the way.

    What did I do wrong? Do you think the dadoes should have been looser in the first place? Or is Titebond III particularly tacky? Or is it possible that the Ash expanded enough to make a difference after I stained and applied water-based poly (the dado parts were taped)?

    All I can think to try is to to sand the dadoes on the other side a bit, and use Gorilla glue. I've not had this problem with that glue in the past. But I've also never made a dado in the past

    Thanks in advance.
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  • #2

    Re: How loose should a dado be?

    Did you do a dry fit before applying the glue?
    I think that, yes, you should have dry fit and sanded or ever so slightly increased the size of the dado and dry fit again to see how tight it was.
    Sanding is probably all it needed.
    I have never had a problem with Titebond III.
    Previously Wallace's Dad

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    • #3

      Re: How loose should a dado be?

      I find that all Titebond glues set real quick. In making kitchens I make a lot of panels and a few doors. If when putting even doors together inserting the rails into the stiles you need to act quickly as a hesitation will result in the joint setting up and as you experienced you have to clamp the hell out of it to get it tight. I switched from Titebond 3 to original Titebond which some say gives you more time .
      Brian
      If your dreams don't scare you, you are not dreaming big enough

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      • #4

        Re: How loose should a dado be?

        Yeah, it's certainly not uncommon when first using dado joinery to get things too tight. I usually aim for a "slightly sloppy" fit, as terrible as that may sound. And the amount of "slop" to build in depends on the material (plywoods will pose less of a problem than solid wood, and of the wood species, some tend to swell more quickly than others) and as you've seen, the glue. In most cases choose a glue that sets up very slowly to provide you the time needed to get things together. There are times when I've resorted to epoxy because they won't swell the wood fibers.

        And ensure you have everything at the ready:
        1. dry fit completed so you know the most efficient may to assemble everything.
        2. clamps laid out in more or less the same location as they'll be needed, and opened enough so they can be quickly set into place and engaged.
        3. non-marring mallet (deadblow hammer is best) at the ready.
        4. glue and applicators ready.
        5. an assistant ready to help you out if you reach one of those "help!" moments when everything binds together.

        Good luck with this.
        KenL likes this.
        All the best,

        Marty

        - Instagram: @apexwoodworks
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        Secretary of Kingston Wood Artisans Inc. https://kwoodartca.wordpress.com/

        Master Mistake Fixer (because I've made them all... at least once)

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        • #5

          Re: How loose should a dado be?

          Hi, you've received some great advice above.

          In addition remember that glue takes space, and it has water in it so it swells the wood pieces. You have to leave enough room for that or you won't be able to assemble the pieces.....Rod.
          Work is the curse of the riding class.

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          • #6

            Re: How loose should a dado be?

            Good advice but my vote for the actual problem is the wood swelling with the application of the glue and the fit being snug to start with. I'm with Marty in the "slightly sloppy" camp for lots of things. Over the years I've had a lot more grief trying to get various things assembled with a tight dimensions.
            billh

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            • Thread Continues Below...

            • #7

              Re: How loose should a dado be?

              I've had good luck with titebond polyurethane glue not swelling tenons in mortises. I don't really do dados and plywood but I can imagine it would be effective.

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              • #8

                Re: How loose should a dado be?

                You said you used a water based poly & stain before glue up. Water swollen wood and a water based glue eliminated the spacing you allowed for.
                smallerstick likes this.

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                • #9

                  Re: How loose should a dado be?

                  Did you apply glue into the dado slot?
                  or on the end of the planks?

                  if you add glue to the end of the plank it will cause the wood to expand enough to make a semi-loose fit SNUG.

                  I try to remember to make the dado a bit looser than feels comfortable.

                  OR

                  add glue into the dado, so the plank won't swell until it is in the slot.
                  [insert something witty here]

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                  • #10

                    Re: How loose should a dado be?

                    I have some concerns on the idea that leave it loose and it will swell the wood. I agree it will swell the wood but as the glue dries the wood will also shrink and I see that as the start of a loose joint. I have experienced this first hand years ago on a table top that I glue up with kiln dried hard maple. I glued it up one evening and sanded the joints the next morning, sprayed it and next day off to NS with the table. Returned to NS a month later. Sitting in the living room looking at the table with the sun shining across it and each glue joint had shrunk into a valley. Lesson learnt.
                    Brian
                    If your dreams don't scare you, you are not dreaming big enough

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                    • #11

                      Re: How loose should a dado be?

                      I'm not so sure the wood would swell as much as you've described in the brief time you applied glue and assembled the joint(s).

                      How long did you wait between cutting the lumber to final size and assembly. If it was a few days, that might be it. And, as asked above, did you dry fit all the joints.

                      I once read the expression that went something like, "you should be able to assemble a housed joint by banging it together with your hat." In other words, tight enough but loose enough.

                      Howard

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                      • Thread Continues Below...

                      • #12

                        Re: How loose should a dado be?

                        Originally posted by mocphatvn View Post
                        Hello

                        I'm making a cabinet that's assembled entirely using dados. I've cut them to be just a couple of hairs bigger than the planks, so that I can insert them without hammering, but they're not loose.

                        WELL SAID


                        Thanks in advance.
                        Simple - you have too much glue in place. - use a small flux brush to brush (spread) the glue to look like a room wall that's just been painted with latex paint. That's all.

                        Also check the TBond labels - I think TB II says it has the longest open time. Check their web site for the differences in characteristics between the three.

                        How about cutting a dado in a piece of scrap and place a scrap pice in it as test joint first?
                        Start slow and wind down gracefully

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