Well, here’s what I came up with (see image file). The USDA Forest Products Labratory says that wood doesn’t start shrinking until it’s down to 30% moisture content. Below that the shrinkage is pretty much linear.
So, for instance, a Southern Red Oak board that was 10″ wide at 12% moisture content would shrink about 0.2″ as it dried to a 6% moisture content. A 20″ wide glue-up would shrink twice as much, or, almost 1/2″. And, going from 6% to 12% it would expand the same amount.
Southern Red Oak and Sassafras are pretty much the extremes, with all other American hardwoods falling in between.
I’ve printed a copy to hang up in my shop.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood
Replies
Here's an EMC chart I've hosted on my site for years that might be a nice addition to your chart.
http://furniturecarver.com/emc.html
Lee
Hey Lee -
Yeah, I got that chart too. But it won't tell you the present condition of a board. It just says that at a given temp and RH, what moisture content a board will stabilize at (Equilibrium Moisture Content) given enough time at that temp and RH.
Since temp and RH vary throughout the day, how would one use that chart?
PlaneWood by Mike_in_Katy (maker of fine sawdust!)PlaneWood
I used your chart.. Great.. I cut the wood, jointed.. Then it rained!
Just funnin ya!
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