# Wood Expansion/ Dissimilar woods



## SteveKorz (Mar 25, 2008)

I have a couple projects in mind where I may glue up dissimilar woods together. Whether it's edge gluing for a panel, or face gluing for a thick workbench top, I don't want to worry about this ruining my project.

My question is, do I have to worry about the two dissimilar types of wood experiencing different rates of wood expansion and ruining the joint, or warping the project? Or, will the expansion difference be so minimal that I don't have to worry about it?

Thanks in advance,

Steve


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## cabinetmaster (Aug 28, 2008)

What kind of woods are you talking about? I have taken and glued a lot of different woods together for cutting boards, tables and turnings and have had no problems with them. The woods I am talking about are maple, oak,hemlock,walnut, mahoganey, hickory, alder, etc.


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## SteveKorz (Mar 25, 2008)

Well, I've been tossing the idea of a traditional oak workbench for some time. I think I would like to face glue 3/4 inch strips of 2 1/2 inch oak together for the top, with walnut stringers for the dog holes.

I've also thought of (on a different project) face gluing pine with hickory. This is the one (soft wood to hard wood) that I could imagine would give me the most trouble. The hickory would be the part of the workbench you would see and work on, the pine would just add weight and thickness, instead of the entire top being made of hickory.


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## Karson (May 9, 2006)

Most wood expands and contracts on the width of the wood. As the tree grows. There is very little expansion or contraction on length. So if you are glueing edge to edge, you shouldn't have any problems End to end might.

You need to also realize that not only might wood expand and contract it might also have an ability to be compressed. So if one board expanded into another the second might be able to be compressed when it could accept the extra movement.

The Wood Handbook from the US Forest service has more that you'd ever want to know about the properties of wood.

You can download it to your computer. They also have lots of other publications.


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## Moai (Feb 9, 2009)

In a FWW magazine, a well known cabinetmaker says this:
"....I used quartersawn maple, but you might want to jazz up your project by using several different woods. That's OK if the different species are, about the same density and will move with the seasons and wear at similar rates" 
Fine Woodworking Magazine No.53, July/August 1985. Pag 65.

By the way, the article is about a Workbench project…


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## JohnGray (Oct 6, 2007)

Steve,
Wouldn't it be easier to go to Boo's and buy the top or parts of it? LOL
John


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## GFYS (Nov 23, 2008)

While it is true wood will shrink and expand more transverse to the grain it will indeed expand and shrink in it's length. The amount that it shrinks or expands in it's length is proportional to the total length of the piece. While 1/100 of an inch per foot maybe considered minimal expansion/contraction in a 6 inch length, if the piece of wood is 16 feet long the shrinkage or expansion would be nearly 3/16 inch. I recently experienced some rather disappointing results in a residential trim out project in a building with infloor heat that made the building humidity so low it broke almost every face frame joint and opened every trim joint in the whole project.


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## SteveKorz (Mar 25, 2008)

Karson and doubthead- Thanks!!

John- I've thought about that… LOL

mics_54… Yikes… that's a bummer…


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## FJPetruso (Mar 29, 2008)

A couple of key points in reducing the difference in the expansion of two types of wood in a project… would be to make sure that the different types of wood be brought into the shop well ahead of the start of the project so that the moisture level in the woods has had plenty of time to balance. You should also finish the interior of your project & seal up (as much as practicle) the interior as will as the exterior. Naturally it doesn't have to look as pretty as the exterior but is should have some finish on it so as to reduce moisture absorbsion.

You know what it's like to purchase 2×4 lumber at a hardware store only to have it twist while drying out at home. It's because they store the wood OUTSIDE & only bring it inside just prior to selling the wood. Even if I have a project requiring 2×4s, I bring the wood into the shop, bundle it up into large bunches & bind it up with ratchet straps at both ends & the middle. After several weeks of drying inside, the straps are released & I find much less twisting, winding & warping of the lumber. A project like mics_54 told about is a good example of how important this acclimating time is.


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## GFYS (Nov 23, 2008)

Fj you are right on about retail lumber sellers keeping "kiln dried lumber" out side untill its sold..it's also shipped with minimal protection. Who knows what the moisture content is after it leaves the production facility. I let all lumber materials acclimate within the building it's being installed. My project wasn't due to that. It was due to the heat system and an exceptionally cold dry spell we had with no humidifier or air changes in the building. I have in 35 yrs as a trim carpenter never seen anything like this. The shrinkage occurred long after the material was "acclimated" , installed, stained and top coated.


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## Sawdust2 (Mar 18, 2007)

I've got a program that is a wood movement calculator.

If you'd like it send me your regular email address.

Lee


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## pitchnsplinters (Dec 26, 2008)

I'd be more concerned that they just wouldn't get along. Arranged marriages can be full of trouble. I'd lay the two pieces on the bench and wait for a natural union. Quintessentially harmonious.


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## FJPetruso (Mar 29, 2008)

Most of us won't see the combination of an exceptionally dry season & a heating system that excells in drying out the house very often. So if we take reasonable care in the handling of our lumber prior to & while working on a project, we might have some shrinkage, but we probably will not encounter a once in 35 year exception like that.


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## Gofor (Jan 12, 2008)

Combining hickory and pine will cause different expansion rates in the two woods. I beleve you will have problems overlaying pine with hickory.

Oak and walnut are close enough that it should not cause a problem.

As for Kiln-Dried construction pine, it only has to be dried to below 20%. That isn't even close for furniture work even if it isn't exposed to the elements.

Go


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## Sawdust2 (Mar 18, 2007)

Just so I don't get inundated, here is a direct link to the program

http://www.woodcentral.com/bparticles/bpindex2.shtml

It's at the bottom of the page.

Lee


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## SteveKorz (Mar 25, 2008)

Thanks Lee… !


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## EEngineer (Jul 4, 2008)

Karson -

What a fabulous resource! As an engineer, I've been drooling over this document all morning! This is a great addition to my technical library. THX!


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## DrEM (Mar 13, 2010)

Hello all!

This is an older thread, but seems relevant to something I'm trying to do but am still unsure on. Basically, I am trying to fix Maple wood (which will be stained and probably varnished+polished) onto MDF, on face with glue. The dimensions of the wooden insert will be 385mm x 245mm, the grain running down the longer length.

This is for a speaker enclosure project, the CAD attached might help show what I'm trying to achieve:

http://img716.imageshack.us/img716/1414/speakerinblackutileroun.png

And fuller details are in this thread:

http://www.diyaudio.com/forums/multi-way/149246-bass-enclosure-3-way.html

Using the calculator posted above and estimated values I am getting shifts in the order of 1.5mm or so. What would be the consequence of this if glued directly to the MDF sub-baffle? How much might this be reduced by the finishing products?

This is the source of the wood I plan to use:

http://www.slhardwoods.co.uk/ParBoardsTimber.aspx?ID=68

Many thanks for any insight you can provide!


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## Karson (May 9, 2006)

Years and years ago I glued some bandsawn cut walnut on some plywood. I used contact cement (This was before I really got into veneering) and the veneer contracted and I ended up with a small gap. If you use PVA glue you should be OK. I've glued on Plywood and MDF and not had any problems.


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## DrEM (Mar 13, 2010)

Thanks for your response!

That does sound promising at least. The panel will be 19mm thick in my project. I saw something a bit worrying though while trying to find out more information:

http://www.lungster.com/l/speakers/woodfaq/woodfaq.shtml

That speaker with the crack is built almost exactly as mine will be it appears. Strange how one cracked and not the other. It looks to be bigger than my project, but I still have concerns.

I usually use a PVA based glue with Resin too (Evo-stick indoor), I'm not sure how much 'give' it has. Mabye some silicone based glue will allow the baffle panel to move a bit and reduce the likelyhood of cracking?

Also, how 'powerful' is the shifting effect? Could it even deform the aluminium speaker baskets set into routered out recesses with close tolerance?

Thanks again! Completely unfamiliar with real woods used in this way and when I started I hadn't considered what an issue it could be!

EDIT: I also just stumbled on this:

http://www.humblehomemadehifi.com/The_Monitor.html

where MDF skinned with hardwood (exactly as I intend) seems to be advised and not causing any trouble. Said hardwood appears to be a 'butchers block' type arrangement though as opposed to one solid piece? Any thoughts?


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