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Wood Expansion question

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Forum topic by twobyfour16 posted 11-26-2010 07:36 PM 2707 views 0 times favorited 6 replies Add to Favorites Watch
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twobyfour16

69 posts in 2947 days


11-26-2010 07:36 PM

Topic tags/keywords: bench workbench question joining wood expansion seasonal

So, I’m slowly working on building my workbench. So far, I have the top laminated up, along with some other components for the trestle base. I laminated my benchtop with 62 pieces of hardwood that are about 3/8” thick and 3 1/4” wide. The top is now about 24” wide & 7 ft long. I plan on putting a skirt around it, like most folks do, as well as a face & twin screw end vise. So here’s the question: With the top laminated from so many pieces, am I going to have more or less seasonal expansion across the width of the bench? I’m going to attach the end skirts with a tongue on the benchtop & groove in the end skirt. Do you think I can get away with gluing it the full width, or is that asking for trouble? I want to avoid using barrel bolts & make the entire bench out of wood.

-- Allan, Portland, OR


6 replies so far

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GaryL

1094 posts in 2293 days


#1 posted 11-26-2010 07:42 PM

Your still going to have the same amount of expansion and contraction as if it were a solid piece of hardwood. It will be more structural stable though because of the multiple laminations. The end skirts will still need to be designed with movement in mind.

-- Gary; Marysville, MI...Involve your children in your projects as much as possible, the return is priceless.

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RalphBarker

80 posts in 2232 days


#2 posted 11-26-2010 07:48 PM

I agree with Gary. You likely won’t have a lot of expansion across the end of the bench, but you’ll still have some that needs to be accommodated.

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Bill Davis

226 posts in 3386 days


#3 posted 11-27-2010 12:27 AM

Wood is hygroscopic which means it take up moisture and give up moisture as the %RH increases and decreased. In doing so the wood will expand and contract and even a good finish will not prevent that, only slow it down. Wood expands roughly twice as much tangential to the growth rings as it does perpendicular to them and a negligible amount along its length. With a lamination the grain directions are mixed so that will mitigate swelling and shrinking but not eliminate it. How much expansion/contraction occurs is pretty hard to estimate so take some moderate precautions in fastening the skirt especially across the end grain.

Beautiful piece. Will make an envious workbench.

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twobyfour16

69 posts in 2947 days


#4 posted 11-27-2010 02:46 AM

Thanks guys. I appreciate the input. I think I will glue the end skirts on one side, and fasten the other side with a barrel bolt with an elongated hole to allow for expansion. Better safe than sorry. The top has been in my garage for a couple months now & I regret not measuring the width exactly – it would have been a good experiment to see how much expansion I get. It was hot & relatively dry when I finished laminating the top in july or august, and is cold & wet now. Live & learn….
Thanks again.

-- Allan, Portland, OR

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wseand

2754 posts in 2504 days


#5 posted 11-27-2010 03:24 AM

GO DUCKS…....!!!!! That is all. he he.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

View Lumber2Sawdust's profile

Lumber2Sawdust

139 posts in 2327 days


#6 posted 11-27-2010 05:44 AM

I agree with others here. You will have to allow for movement. I recently completed a similar bench. To allow it to move, I glued the first 3-4 inches at the front of the apron, then pinned the tongue at a few places along the length, with elongated holes to allow it to move. I used walnut dowels for the pegs to highlight the contrast. It worked well with some of the other bits of the bench.

EDIT: You can see the pegs in my bench top in my project, posted here.

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