3

About a week ago I took the clamps off a table I am making. I used biscuits to join the boards lengthwise and Titebond III glue on the biscuits. When I took the clamps off the seams looked great. Now, a week later, the seam in the middle of the table has opened up about 1/16-1/8 in and you can see the biscuit. I've tried to squeeze it back shut, but no luck. Any ideas? What about wood filler that I sand off? Or should I slip a hand saw in the seam, cut the biscuits that can be seen and add glue along the butts off the boards?

Thanks- Steve

  • I have had similar things happen when the wood was not 100% dry. after everything is put together the gaps get larger until the wood is dry. – Ed Beal Aug 31 '16 at 19:21
4

It's not clear from what you've written if you applied glue along the joint as well, it sounds like it was just to the biscuits/slots. If so for future reference you need to know the biscuits aren't holding the boards together in a joint like this, they are primarily an alignment aid during assembly.

The glue joint on the board edges provides >95% of the strength in this type of joint (long grain to long grain).

What about wood filler that I sand off?

You can use filler if you like, but a 1/16"-1/8" line of filler won't be very attractive. The main worry would be about structural integrity though, those open joints will have next to no strength and it may cause a problem down the line.

There are superior choices for filler here (epoxy probably being the best and strongest) but since you're willing to saw the panel apart don't worry about that for now.

Or should I slip a hand saw in the seam, cut the biscuits that can be seen...?

That would be the best way to approach this. For someone with a fully equipped shop when something goes wrong with a panel glue-up almost always the advice is to run the problem joint through the table saw and then glue it again.

You can skip adding fresh biscuits this time if you like, but add a couple again if you need the help with alignment during the glue-up. But be sure that you apply plenty of glue to the long-grain edges of the boards this time.

You want to ensure that you apply enough glue that some squeezes out along the entire length of the joint, that's what tells you you applied enough. Clamp firmly as it is high clamp pressure that ensures a good glue bond (don't worry about squeezing out too much glue, this is nearly impossible to do in real-world conditions). You're actually aiming to squeeze the boards together hard enough that the glue joint is nearly invisible, yes, that thin.

In addition to looking better thinner glue lines are stronger than thicker ones with most woodworking adhesives.

Some previous Q&As that might be helpful:
What is a good way to prevent jointed tabletops from bowing when tightening fasteners or the glue sets?
What are the different grain directions, and how do they affect joint strength?
What advantages do F-style clamps offer for gluing up a thick laminate?

| improve this answer | |
  • Another possible solution, if the problem is just one or two isolated separations and it's strong otherwise, you could consider making the gap a design feature and install some reinforcing "butterfly" inlays to hold it together. – keshlam Sep 3 '16 at 0:04
2

Before cutting anything I would suggest you clamp the table back tightly and get your hands on a heat gun and if you do not have that use a hair dryer (requires some patience :) and adjust your clamps as needed to keep it tight until gap closes. Prior to it , brush or squeeze glue in that area. Dry well after achieved. Depending on your finish look, if any. I would consider a frame you can nail around the table or applying an epoxy finish to it. Cheers.

| improve this answer | |
  • 1
    Framing a table, any glue-up really, is fraught with dangers as the frame will try to constrain seasonal movement which can lead to cracking or warping. – Graphus Sep 4 '16 at 6:57
  • Please forgive me If take your words of fraught with dangers as over excessive in description. I was a set builder and general contractor. I am not sure if you are aware that when building sets our best friend is foam. Almost everything in Disneyland is made with 2x2s and foam. So if that were the case I doubt something like foam that has no strength or give would be used in high volume in high traffic public areas and abuse. As for warping goes, It would minimize it. And unless it is outdoors and under extreme weathering, than cracking should never occur. – norcal johnny Sep 4 '16 at 7:07
  • 1
    Framing panel glue-ups is inherently bad practice because it tries to constrain the natural seasonal movement of the boards. It doesn't require exposure to weather. – Graphus Sep 4 '16 at 7:18
  • There are things related to framing that one can do -- installing breadboard ends, for example, to help keep the table flat -- but natural wood does change width across the grain (and may change cupping/bowing) with changing humidity. Any woodworking design has to allow for that. Plywood generally doesn't have that problem, which may be why you didn't run into it in set design and contracting. It also may not be an issue for things which are nailed together rather than glued; nails can sometimes bend enough to keep this from tearing things apart (though joints will loosen as a result). – keshlam Sep 5 '16 at 7:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy