So I decided to learn how to make handmade dovetail joints. I’m in the middle of making a dozen drawers for my kitchen cabinets in some popular. It’s been a lot of fun and I can see my progress in accuracy but then something occurred to me.
Here in New England the humidity outside and inside my house is around 6%. The wood is dry and I’m making these joints tight, a true friction fit that you have to tap together with a mallet.
During the upcoming spring and summer months humidity humidity levels will be around 60% or more. It’s something I really can’t control.
I can just picture my drawers coming apart when the humidity increases and the joints swell and get tighter.
Am I wrong in worrying about this? They are not glued up yet and I can go back and make them a bit less tight by taking more material off. Anyone have experience with this?
No need to worry.
There are three directions in wood-along the height of the tree (along the grain), along or around the growth rings (tangential), and along a radius (radial). Expansion and contraction is almost zero along the grain, is maximum tangentially, and is about half of that radially.
When you dovetail two pieces together, you are aligning a mixture of tangential and radial grains. Both boards are like this. So, they will expand and contract together. Your joints won’t even notice. Even if you use two different woods that have different amounts of expansion, the total expansion depends upon the width of the work, and since drawers aren’t that big, the difference between the two will not be a problem, even for big drawers.
The only time to worry is when you cross long grain with tangential or radial. Even then, you can sometimes get away with it if the dimensions are small.
I’ve talked about tangential and radial grain separately, but most builders just lump them together into “face grain” and only worry about face grain vs. long grain.
So, as long as you put your drawer bottoms in grooves and you do your cabinet doors as frame and panel, you’re good to go.
Thank you for the explanation! I confess I had to think about it for awhile but it makes sense to me now. I have had 11” oak boards split on me while they were in a stack and not restrained so I’m a bit sensitive to wood movement. Ive seen all these pictures of different woods dovetailed together and wondered how long they would last.
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