[Noumenon]

I usually don't try to glue dissimilar woods together because of the mismatched expansion factors. However, I have some dark lyptus that would look really nice contrasted with some white hard maple on a project I'm doing. I want to glue a length 6 inch 1.25 inch wide of hard maple to a matching piece of lyptus. Are the coefficients of expansion so different that the bonds will break or something else bad happen? I am finishing both with polyurethane.

I know most of the contraction/expansion (due to moisture) is in the cross grain direction. I will, therefore, have 1.25 inches of cross grain expansion differences between lyptus and the hard maple. Both are hard woods.

The woodworking database says:
Lyptus Shrinkage: Radial: 8.2%, Tangential: 12.8%, Volumetric: 21.0%, T/R Ratio: 1.6
Hard Maple Shrinkage: Radial: 4.8%, Tangential: 9.9%, Volumetric: 14.7%, T/R Ratio: 2.1

These seem too different to be safe.

Your thoughts?

 

[Jim Frye]

What kind of joinery will you use between the two woods? Are you joining end grain to end grain? Long grain to long grain? end grain to long grain? Finishing all surfaces with the poly? How thick is the 1.25" wide wood? Worst case expansion of the unfinished wood is about .10" (1/8").

 

[Noumenon]

Long grain to long grain, basically one layer on the other.
I will glue them together before finishing with poly.
Thickness of the maple is 1.25 inches.
Thickness of the lyptus is 3/8'ths of an inch.

Thanks for the reply.

 

[Noumenon]

Cutting Boards w/ Lyptus and Maple

I've read where cutting boards are sometimes made with lyptus and hard maple. If it (gluing lyptus to hard maple without problems due to mismatched expansion/contraction) works for cutting boards, then it should be fine for my application.

 

[Larry42]

Lyptus (Eucalyptus) has stability problems. BUT if both the maple and the Eucalyptus are of the same moisture content when glued and the surfaces are fresh and parallel you will likely get away with it. Now if the product is put into an environment where it changes moisture very much the result will be a bit of cupping. Seal the end grain really well as that's where the quickest absorbsion will occur. Do you have a moisture meter?

 

[Noumenon]

Thanks a useful reply, Larry. I do not have a moisture meter but live in a very dry climate in Colorado. Both of the woods have been drying in my garage for over 10 years.