Cutting board and workbench grain orentation?

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Forum topic by dalethewhale posted 11-10-2014 04:44 PM 1030 views 0 times favorited 5 replies Add to Favorites Watch
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19 posts in 1852 days

11-10-2014 04:44 PM

G’day guys,

Lets just say we’ve got some 2×4’s and we glue them up into a wider board.

I would assume that you put the glue on the 2’ sides as the this is the ‘thickness’ part of the timber and it will now be allowed to have it’s seasonal movement across the ‘width’ of the pieces (the x4’s). In this scenario the glue would not really affect or resist the ‘latitudinal’ movement.

However, if i glued them together along their 4 inch sides, like i see in a lot of workbench builds,it gives me a much thicker board but wouldn’t those glue seems resist the movement of a board that wants to expand up and down instead of ‘across’? Wouldn’t the boards or benches tear themselves apart?

Cheers in advance


-- Merrily, Merrily, is but a dream - Whale, Coffs Harbour, Australia

5 replies so far

View bobro's profile


320 posts in 1339 days

#1 posted 11-10-2014 07:55 PM

When you glue pieces of wood together, you theoretically get one big board. So theoretically a workbench top of flatsawn 2×4s oriented to so it’s 4 thick would move primarily in the vertical axis, as one big beam. When glued side to side, a 2 inch thick tabletop, the movement would be to the sides, as one big board.

If you cut a piece of wood and glue it back where you cut it, this does indeed act once again like a single timber, but if you glue various pieces of wood together, the movement tendencies of each might be close enough to not matter, or they very well might be contrary to each other. So you might be in essence creating a big piece of tension wood. Of course you might want to do this, deliberately, for example in the case of “smile, frown, smile..” orientation of flatsawn boards in a tabletop. The cupping tendencies (outward from the heart of the tree) will cancel each other out to a greater or lesser extent.

In the case of a bench top glued up from a bunch of flatsawn 2×4s, oriented to 4 inches thick, twist, cup and spring in the individual boards are almost certainly going to be canceled out overall. It’s possible though unlikely that you might get unlucky and glue several boards together at the edge that all have the same tendency in terms of bowing. This could make one corner of the table pop a wheelie, or take a nose dive. You’d have to be really unlucky to get enough similar spring tendency going on to bow the top as whole.

I have seen an IKEA tabletop, made of machine-scarfed boards glued up in flatsawn orientation, bow as a whole, so looking down it didn’t look like II, but ((. And somewhere I have a chunk of birch salvaged from some other IKEA thing that’s laminated up from several pieces and on paper should be extremely stable, but it has a strong twist. Lamination isn’t magic, you have to think about orientation and choose the best pieces you can.

By the way it isn’t strictly true that you get a quartersawn top by turning flatsawn boards on their sides and gluing them together. It’s more of a sort of, sometimes, depends thing. You weren’t talking about that but it’ll surely come up.

Hope this is helpful- it’s so much easier to discuss when you can draw what you mean as you go.

-- Lao Ma: You are so full of anger and hatred. Xena: Everybody's gotta be full of something.

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19 posts in 1852 days

#2 posted 11-11-2014 01:00 AM

Thanks for your reply mate. I appreciate the effort you went to.

I too longed for a piece of paper and the ability to draw some rectangles when writing my question!

If my bench top of 2×4’s if glued up so it is 4 inches thick , i understand that it should expand and contract vertically.

What i don’t get is how does it if there is glue in between the pieces. ‘If’ the glue between them does’t expand and contract. Or does it?????


-- Merrily, Merrily, is but a dream - Whale, Coffs Harbour, Australia

View AandCstyle's profile (online now)


3075 posts in 2286 days

#3 posted 11-11-2014 02:29 AM

Ideally the space between the boards whether they are side by side or are edge to edge will be the thickness of one glue molecule so the expansion/contraction of the wood will not have any impact on the glue. Expansion/contraction only become an issue when you attempt to prevent the wood from moving such as in a cross grain situation, e.g. screwing a top to the end apron of a workbench without elongating the holes. HTH

-- Art

View brtech's profile


1029 posts in 2951 days

#4 posted 11-11-2014 02:29 AM

Yeah, it does. The amount of expansion/contraction of pine over 4” isn’t much, and the glue gives a bit. Using longleaf pine, initial 3%, final 10%, 3.5” nominal, I get 1/16” movement, but that’s over the whole width, an individual spot grows a whole lot less than that.

View bondogaposis's profile


4770 posts in 2380 days

#5 posted 11-11-2014 03:04 AM

Modern woodworking glues have flexibility built in to accommodate wood movement.

-- Bondo Gaposis

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