Wood expansion

[rgdaniel]

Hi folks...

I know that a board will expand more across its width than along its length... but is there any difference in expansion rate in the up/down vs the left/right of the width?

Reason I ask, I want to make some multiple species cutting boards, composed of strips of cherry, walnut, purpleheart, and maple. The maple I have is 8/4, the rest is 4/4, so to avoid resawing, I want to cut strips of maple with its face grain facing up, but the other woods would be cut wider, and flipped 90 degrees to present edge grain to the user. Is it the same difference as far as expansion goes? At least, is any differential likely to be on the order of the differential between the species, such that when all glued up, and at cutting board sizes especially, nothing's going to blow apart from different expansion rates?

photo from Fine Woodworking:

Thanks, cheers!

Bob.

[PaulMarcel]

I'd say you'll be fine.

Long grain expands across its width. How much depends on where the growth rings are; you have radial and tangential expansion ratios that are different. Expansion along the long grain is next to nil. The orientation of your pieces will dictate which ratio is key. Since the pieces you are gluing together aren't that wide at the glue surface (the constrained surface) the glue and local fibers take up the stress differences between expansions of the two species. Note, too, that even if you made it all of maple, there could be stresses there as each board's starting moisture content and internal stresses make the boards different.

blah blah blah, kinda got on my own tangent there, sorry...

[rgdaniel]

I'd say you'll be fine.

Thanks!! I was probably over-thinking as usual...