I see a lot of back and forth about what one should use in a glue up of a table top. Some tend to use dominoes while others use dowels or biscuits.
Is it ever completely necessary to use any of those? Couldn’t you just as well use nothing but glue? Or is there some length beyond which a different type of joinery is necessary to accompany the glue up (day, of an 8 foot table).
Replies
Glue is all you need for edge joining boards. Biscuits, dowels, dominoes, etc all add nothing to the strength.
What they can do, in an 8 foot long table, is help align the two boards while you clamp them. If the boards have a little bit of bow in them, it can be a pain to keep them even. But, if your buscuits etc are misaligned at all, it will be impossible to keep them even.
Cut your boards to size and line them up. If it looks like they will glue up evenly, glue them. If there is an issue, consider an alignment aid.
John_C2 has it all down here. One more aid for boards that do not seem to need alignment help is an anti-slip strategy. Glue is slippery and clamps don't often go on perfectly, leading to sliding along the glue line. Consider driving a few brads into one edge, leave them 1/8" proud and snip off the heads. Do a dry run through your clamping sequence, the brads will give you the help you need.
Long grain to long grain edges will glue together very strongly assuming the faces are flat and meet well, the glue is good stuff and the clamping applies the right degree of pressure between the faces. As another says, the issue is often the alignment of long pieces. If they're also thin, it can be harder to keep them in alignment as you glue and clamp them up.
One additional issue can occur with oily woods like teak. If there's a significant amount of oil in the edges to be glued, the glue will struggle to get into the wood cell structures to do it's binding-together thing. You can help it by wiping off the edges with alcohol to suck out or dilute the oil; but biscuits and dominoes might, in this case, add some binding strength as well as alignment help.
Biscuits, dominos, splines and similar mechanical additions to the face-to-face glue joins can mostly help to keep the boards in alignment, though, as the boasrds are stuck together. Of course, the biscuit/domino slots or spline grooves have to themselves be accurately made.
Another method of aiding alignment of multiple planks being glued together is to use cauls. These press on the unglued faces of the boards to press them flat and into alignment before the glue-clamps are tightened up on the edges being glued. There are variations of cauls.
Some folk make them out of simple straight pieces of wood that are mounted across the boards being glued up, one of each pair opposite the other on either face, then themselves clamped to press on the faces of the boards. They need to be waxed or otherwise prevented from sticking to any glue squeeze-out.
Another method uses such pieces of wood but combines them with the clamps used to press the glued edges together. Here is a Veritas version:
https://www.leevalley.com/en-gb/shop/tools/hand-tools/clamps/31181-veritas-panel-clamp
Yet another method employs a dedicated metal jig to clamp boards together in a vertical orientation, with the clamp pressing not just on the top and bottom edges but also on both sides of the faces. The Plano press is the best-known example:
https://advanced-machinery.myshopify.com/pages/plano-vertical-glue-presses
One advantage of the Plano-press is that it can be mounted on a workshop wall, with it's vertical orientation keeping large glued-up tabletops and similar out of the way. It's easy to load the press with one edge-glued board at a time then squeeze the whole assembly together in one quick operation.
Mind, these commercial jigs are not inexpensive.
Lataxe
I can help with that. Right now, a lot of people have trouble finding the right wood glue. There are many factors to consider, including which tree it is, what you are going to glue and how you are going to glue it, and what the end goal is. I am a repairman myself and do just the same installation of wooden furniture, gluing and so on. I can already say from myself that I recently engaged in gluing cork wood. It turned out to be a difficult business, but it was also necessary to carefully select the glue. Then I studied an expert article about glue for balsa wood https://gluefaq.com/best-glue-for-balsa-wood/ and picked up a suitable glue there. I think it would be useful for a lot of glue people. I personally took Gorilla Wood Glue, as I used it for other purposes as well. It worked just as well here, because I think he can handle such a trivial thing as gluing piles on a worktop. But there are other options, think for yourself and choose the right one. I hope I've been able to help someone.
Only thing I can add is I like Old Brown Glue for edge-to-edge gluing. Downsides are it has to be kept warm to work & it has a short open time (20 minutes.)
I have done plain, spline, Domino, etc. The additions are to help with alignment while you are getting things in the clamps. After that they are just interruptions in a clean long grain glue surface. I prefer to do without. If something about the assembly makes things a bit unwieldy I will add something.
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