I did a search here and on the internet but did not find a clear answer to the question:
How much does red oak expand as humidity changes in a house?
I have gotten answers like 1/64″ in 2″ online and 1/8″ in 12″ from local Woodcraft store.
Is there much variation among species? I would guess that the more prominent the grain, the greater the expansion/contraction; fir&pine greater than oak, oak greater than walnut?
BruceT
Replies
This book has a lot of great info on expansion as humidity changes etc. including color photos of most of the commonly available woods with various finishes on them including exotics. Over all one of the best wood working books.
roc
Give me six hours to chop down a tree and I will spend the first four sharpening the axe. Abraham Lincoln ( 54° shaves )
Edited 12/7/2009 9:52 pm by roc
And the book is...?
BruceT
> and the book is<http://www.amazon.com/Nick-Englers-Woodworking-Wisdom-Cabinetry/dp/0875966519/ref=tmm_hrd_title_0Oooouuuuuups ! Blush.Now howd that happen.I'll blame it on the big Fine Woodworkng .com change over. Yah that's the ticket.: }rocGive me six hours to chop down a tree and I will spend the first four sharpening the axe. Abraham Lincoln ( 54° shaves )
Edited 12/9/2009 6:26 pm by roc
Thanks for the link. Enjoy Knots while you can. The new "improved" version will be like the new BT and CT - absolutely awful.BruceT
Put your parameters in here -
http://www.woodweb.com/cgi-bin/calculators/calc.pl?calculator=shrinkage
The question has a precise answer but the way you phrased it leaves it open to interpretation.
David Ring
http://www.touchwood.co.il/?lang=e&id=1
That is a handy tool Mr. Ring. I'm willing to accept the results, but it would be nice to know exactly what the calculations are. If I weren't so lazy I could make a number of sample calculations and compare them to the results of the tool. If you know the calculations and would give them you would spare and old, lazy guy some work. Thanks
Ron
The basic formulae can be found in a book every serious woodworker should either own, or obtain from his library. That is R. Bruce Hoadley Understanding Wood, Tauton Press. It devotes chapter 4 to "Water and Wood".
For a great on-line source, with the formulae, you can visit the web pages of the U.S.D.A. Forest Products Laboratory Handbook, Wood as and Engineering Material http://www.fpl.fs.fed.us/research/difference/handbook.shtml
By the way, the likely biggest difference between the calculated results and in-home results, is that the calculations assume that the wood moves from equilibrium at one level of humidity to equilibrium at the other. But this takes time. And, in particular, it takes time if the wood is finished. Shellac in particular slows humidity transfer into and out of wood. Finish can mean that by a seasonal peak in humidity doesn't have time to create a full equilibrium expansion before seasonal decreases in humidity start to contract the wood in reaction to lower moisure. Finishing doesn't stop moisture flow, but it does slow it down.
But, of course, all this wood movement is precisely why frame and panel doors were developed. It wasn't just a style thing by any means.
Edited 12/8/2009 11:52 pm ET by SteveSchoene
I've been pondering a similar question about wood movement with respect to a maple workbench top. In Garrett Hack's article about his new work bench he used dovetailed end caps on his top. They look great and I'd love to use them on my latest bench but I can't help but feel a little uneasy about the prospect of my dovetails popping apart with expansion and contraction of the top (even with elongated bolt holes and limited gluing). I suppose clever engineering of the tool tray offers some potential for accommodating the movement but I'd be interested in hearing what people think. It seems that I've often read articles and posts that say something to the effect "I glued such and such in a cross grain situation but it's never been a problem" I'd love to be THAT guy but given my past luck.....I originally posted this under another topic but got no feedback. Thanks
Neil
Bruce, I'd make a guess and say flatsawn red oak can move close to 3/4 of an inch across a 36" table top. Movement will vary by conditions, species and sawyer properties. Frinstance, quarter sawn stuff will move (across the board) a lot less than flatsawn stuff.
Somewhere there must be a text on this info.
Denny
"How much does red oak expand as humidity changes in a house? "
This is a trick question! ;-)
A couple of years ago, I saw a cabinet door in FWW that I liked, and I wanted to make some with a similar design. The problem was that the design required either laminating oak to plywood to make a door panel or inventing some other solution. The reason for this was that the door I liked looked like a single slab, about 16" wide. Because the design lacked the traditional frame & panel construction that inherently compensates for wood movement, clearly this was an invitaiton to problems from; a) expansion/contraction issues, and b) cupping, warping, etc.
I planned to use white oak and consulting various tables led me to the conclusion that white oak was among the worst for wood movement and the door I planned would move about 1/4" as humidity seasonally varied. Not good. (One of the best sites for calculating wood movement is: http://www.woodbin.com/calcs/shrinkulator.htm )
But the skeptic in me wasn't convinced, so I reverted to scientist mode and tried an experiment (which is still ongoing). I made a set of doors out of white oak -- not quartersawn, since I had none on hand, but plain sawn lumber left over from a construction project -- attached them to a cabinet, and sat back, for about a year and a half now, and watched to see what happened.
Answer: Pretty much nothing. There was some movement and the doors got a bit tighter in their openings during the summer, but nowhere near 1/4" -- more like maybe 1/16" -- if that.
Here's a shot of one of the doors. It was taken shortly after I assembled the cabinet, in the winter, when one would expect the wood to be at the narrow end of its movement cycle. I fit the door just a bit loose but, based on my research, I expected to have to plane it to final width the following summer as the wood expanded:
View Image
Well, summer has come and gone, and no planing was needed. The gap on the left closed a bit, but the wood never expanded enough to affect the door's operation. No planing needed.
As for keeping the panel flat, I added walnut battens at the top and bottom, fit into a sliding dovetail, glued for about an inch or two at the hinge side.
View Image
Again, I really didn't expect this to work, since there wasn't much walnut in the batten. But again, no problems in about 18 months now. And it's also worth noting that the doors hardly moved at all with respect to the battens, which was another problem that I expected, but thankfully did not experience.
Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.
Edit: Forgot to mention that the piece was finished with clear Watco and shellac. Forced air heat, Pittsburgh climate. Which, now that global warming has arrived, is a pretty darn great climate to live in!
Edited 12/8/2009 8:02 am ET by MikeHennessy
I love that walnut batten or breadboard or whatever you want to call it. Slick idea.Perhaps things don't move as much as anticipated because your have an air-conditioned house in the winter and maybe hot-water heat or a humidifier in the winter? Or you live somewhere that the humidity does not change too much?I live out in the timber along a river in Iowa. In the summer, we keep the house wide open and humidity can be very high. In the winter we use woodstove heat or forced air. The flux in humidity from one season to the next is borderline ridiculous.
Per my prior postscript, I live in Pittsburgh. We're pretty skimpy on the AC in the summer, and the heat is forced air, with minimal added humidity (or else the windows fog up.)
I guess the bottom line is, if you've got the time, try a piece of your chosen wood, with your chosen finish, in your particular environment. You may be pleasantly surprised, as I was.Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.
Really nice piece, Mike. Thanks for posting it.I'm not bright enough to have thought of using that solution. ;)Leon
As others have said, the movement is determined by a number of factors, but particularly changes in relative humidity. If you build a panel 300 mm wide out of red oak that's at about 8 or 10% MC and then put the piece into a typical house where RH ranges from about 40% (winter) to 60% (summer) then the piece will probably range from about 7% MC at the end of the driest period of the year up to about 11.5 MC at the end of the most humid period.
A red oak panel 300 mm (~12") wide made of tangentially sawn planks might vary in width by about 4 mm (~5/32") over a season. American red oak has shrinkage factors of 8.9% (tangential) and 5.3% (radial) from 30% MC down to 0% MC. In service in a house you only need to concern yourself with the MC range the wood will experience there.
As Mike described in his post, he's not had any significant trouble with his panel, so it's not always the case that you'll get the movement you can calculate that might occur. Polish delays movement of water vapour in and out of wood, and people experience different typical seasonal RH conditions in their homes depending on where they live and how they run their climate control systems. I have found that 60% RH during summer and 40% RH during late winter are fairly typical of most houses around the world, so I use these numbers when I calculate allowances for wood panel movement. It's not perfect, but it's reasonable. Slainte.
richardjonesfurniture.com
Edited 12/9/2009 3:25 am by SgianDubh
Richard:
Thanks for taking the time to help with some practical suggestions. I made a note of them, now how to avoid losing the note . . .
Bruce: The book that "roc" was referring to may have been "Understanding Wood: A Craftsman's Guide to Wood Technology" by R. Bruce Hoadley.
Here's another one that I use.
http://woodbin.com/calcs/shrinkulator.htm
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