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Edge Gluing Panels

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  • Edge Gluing Panels

    Happy Thanksgiving, y'all!

    I'm edge gluing three 3/4" x 30" x 7" poplar wood to make a toybox lid, which will be painted. I decided to use biscuits for additional reinforcement. I'm having a hard time getting the long seam to line up during glue-up and clamping. In one area, it's about 1/64 off. (yes, wood was planed to a common thickness.)

    Is 1/64th an acceptable amount that can be "adjusted" after glue-up, given that it's going to be painted? I used a card scraper to even the edge, with decent results.

    Also, I'm almost wondering if using the biscuits is counterproductive. It seems that the biscuits expand and get so tight that I can't do any adjustments to line up the edges during clamping. I know that a good glue will theoretically make a bond stronger than the wood itself, but I guess I have a natural mistrust of just using glue.

    Regardless, I'm going to have to saw through one of my joints and redo it, as there's a .01 gap on one side....bad clamping technique, obviously.

  • #2
    Re: Edge Gluing Panels

    Could be a problem with cutting the biscuit slots. Sometimes the base of the cutter rests on the bench instead of the fence resting on the top of the wood which causes offset issues. The slots are almost never perfectly centered so make sure you always keep the same side up when cutting and gluing. You can always smooth the surface after the glue dries with a scraper or plane. If the biscuit slots are cut correctly you should have no play to be able to adjust the surface alignment.

    If there is a gap on one side and none on the other the issue may be that the edge was not jointed perfectly 90 to the face


    • #3
      Re: Edge Gluing Panels

      I don't know that it's really necessary to use biscuits at all if the top is going to be flat anyhow, it's not hard to do a flat glue-up to begin with and you'd probably have less trouble getting everything aligned without the biscuits. The glue is a lot stronger than the biscuits anyhow.

      The only time you have to worry about swelling with biscuits is when you're joining thin stock, the swelling of the biscuits can cause bumps initially and if you sand or plane them down, when the biscuits shrink again, you'll get low spots in your project. With 3/4", I wouldn't worry about it.


      • #4
        Re: Edge Gluing Panels

        Yeah, forget the biscuits. With long grain to long grain, they are just something to fight with, plus you spent the time putting them there in the first place. With end grain, it's a different story. End grain does not glue well.

        As far as the crooked glue-up...Be sure that the edges are square in the first place and that you clamp them that way in the second place.
        Use cauls to spread the clamping force and clamp from both sides of the boards. This minimises the clamp's tendancy to push a bend into the glue-up.
        Brush the glue in a thin layer onto both surfaces. This gets 100% coverage w/o at ton of sloppy squeeze out. Ideally, you should see tiny beads, no drips. I find it best to leave them and scrape them off after drying. If you get more, let them thicken to near gel and scrape them off with a putty knife. This keeps smearing and absorption to a minimum. It's not hugely important on painted stuff, but it is on everything else. You might as well get the practice. It is best to use good form all of the time.


        • #5
          Re: Edge Gluing Panels

          try checking popular woodworking. they did an article on effective plate joiner use. i vaguely remember the author advocating disregarding the fence in your application in favor of referencing the material and joiner to the benchtop.
          there's a solution to every just have to be willing to find it.


          • #6
            Re: Edge Gluing Panels

            Thanks all for the input.

            For cutting the biscuits, I used my table saw tap (the truest surface I have) as a reference, and ensured I kept the correct sides matched, so it's definitely not a height mismatch. I just think it was the biscuits that prevented me from doing any fine adjustments after I had it partially clamped.

            As implied, I'm going to cut through the existing joints (I have over an inch of extra width on the whole assembly to play with), and rejoin it without biscuits. I like Longhair's idea of using a caul along both edges to get them true. Then I can get the middle adjusted.

            I also think I'll glue up the three sections in two separate gluing steps, just so I won't rush the process, which is my tendency.

            I'd do this today, but the wife spent all morning vacuuming, and I don't want a new coat of sawdust thoughout the house for at least 48 hours.