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I had glued spruce planks together using mixture of Titebond and sawdust.

I had tested such joins and found the bond to be surprisingly strong. For example, I had two short pieces of 2x6 inch spruce boards glued together edge-wise with grain of both boards in parallel, using that mixture. After a few days I tested the bond by hitting the jointed pair of boards against the concrete floor until they broke apart. But the jointed boards split apart along the grain of one of the boards rather than along the edges where they were bonded together. Thus proving the strength of such a bond.

I use this method of bonding spruce boards together because the sawdust admixture fills in the gaps due to unevenness of the edges of the two boards placed together.

Had I planed the edges flat and applied pure wood glue, would the bond had been stronger. Did the sawdust admixture improve or deteriorate the bond, I wonder.

Now I am thinking of building a kitchen countertop by gluing maple 1x6 planks together. I plan to plane the edges even AFAP (as flat as possible) before bonding and clamping them together.

Since 1x6 planks are actually 3/4 inch thick, I plan to glue the planks together in two layers to get a 1.5 inch thick slab. Perhaps by not having the edges of joins of top layer coincide with those of the bottom layer.

The question is: would it be advisable to use purely wood glue or instead have maple dust mixed into the glue? I'm wondering if the saw dust will affect the strength of the bond negatively.

My query does not concern with aesthetics of the bond, but rather the strength and durability of such a bond.

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  • You should ask the maker of your glue if sawdust, and how much, would strengthen or weaken their bond. Most quality brands have customer service phones and email.
    – jay613
    Oct 23, 2023 at 11:17
  • Intuitively (worth, honestly, nothing) it does not. Everyone uses sawdust for color matching. Nobody uses it for strength. If you use only sawdust, it will not be as strong as only glue. Then, if you use 99% sawdust, 98 etc, it will start to become useful as glue, but would it be strongest at some point before you get to zero? I don't think so. You mention gap-filling properties, but wood glue is not meant for that. Yes, mixed with sawdust you can fill some gaps but that's not for strength. Other glues for gap filling, for example, epoxy.
    – jay613
    Oct 23, 2023 at 11:20
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    This is an interesting question. It would be a much better question if you remove the information about your kitchen and just focus on "does sawdust improve the bond of wood glue if the surfaces do not match perfectly", or whatever precise question you have. If you want tips on fabricating your own kitchen counter that belongs in woodworking SE.
    – jay613
    Oct 23, 2023 at 11:23
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    Allow me to introduce you to Woodworking where you'll find all sorts of info about glue joints, strength, glue filling, etc.
    – FreeMan
    Oct 23, 2023 at 12:40
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    This is probably pointless to highlight since this is a migrated Question (if it's not, welcome to Woodworking!) but "Would the saw dust affect the strength of the bond negatively? Would the sawdust admixture exacerbate expansion issues of maple boards?" These are two completely separate queries and should be asked in separate Questions (should your own research not supply the answers of course).
    – Graphus
    Oct 24, 2023 at 22:34

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Mixing the same wood sawdust into wood glue is a very common way to fill holes in boards/slabs. I have never seen a problem in a climate controlled area (i.e. inside the house) with sawdust mixed in glue. As you saw in your experiment, wood glue provides more strength than the wood itself.

The biggest problem you will face with a 3/4" counter is flexing/lack of rigidity; as you noted 1.5" is far better. You should use some sort of a undercounter sheet (3/4" plywood would be great) to provide support and help prevent cupping. I also recommend running supports for the sink (1x4 oriented vertically). You should also seal it to prevent as much moisture from penetrating it as possible; specifically, butcherblock oil or some other food safe sealer if it is going to have food contact.

I made my own oak countertop a decade ago using a very similar process and it worked great.

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    Just as an aside Sean, all the evidence points to all conventional wood finishes as being OK for direct food contact — very much so for incidental-contact surfaces but likely also fine for food-prep surfaces (since there's actually zero evidence they aren't). After the full cure period naturally, and assuming proper drying with anything that has two components.
    – Graphus
    Oct 25, 2023 at 8:21

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