Wide boards unexpected warping

I'm working on a built in bookcase that's just under 8 ft high and 10" deep, made of popular. I picked up a load of 13/16 thick material which included several 8' long boards 11 to 12" wide. I ran these through my planer reducing the thickness to 3/4" but after a day or so a couple pieces warped across the width making them unusable for the sides of the case. I can reprocess the warped boards into shelves so the material won't go to waste. However I'm new to wood working, particularly with projects of this size, so I wonder did I chose the wrong material, process it incorrectly or perhaps this outcome is to be expected occasionally?
Thanks
Robert

The issue here isn't that you chose wider lumber...it's that those particular boards wanted to be a pain. It happens. So...

When you surface lumber, you are "unlocking" moisture and physical stresses that's inside when you take off the surface. It's important to take equal amounts off each side and a best practice to not take it all the way to final thickness unless you are going to immediately use the board(s) for whatever assembly you are making. Take it most of the way; stack and sticker for a day or so and then take to final thickness when you are about ready to need to the components. That said, there is still never any guarantee that a board will stay flat because both moisture imbalances and internal stresses from "growing" are always unknowns. So your very last point is most likely accurate" "perhaps this outcome is to be expected occasionally."

How dry was the wood when purchased. How long did it acclimate to your shop before planing. When building a fence I buy 10%. more lumber then needed. sticker and stack it for a few weeks outside in summer and return the badly twisted stuff.
Bill D

Did you just plane one face? If the wood was a bit wet, unbalanced machining can cause warping. Are the boards close to the pith of the tree? Small growth ring circles can pull if the wood is damp and put in the warp. Tight stacking boards that are slightly damp will expose only one face to your shop air and that causes warp. If you don't have a moisture meter, buy one. If you get wood just slightly damp, stack it with stickers between the boards and let it acclimate before machining.

It's best to bring wood into your shop, put it on stickers, and let it acclimate for at least a week before using it. When you use it, try to take equal amounts off both sides. And DO NOT leave freshly planed lumber flat on your work bench for any length of time. Any change in MC will cause it to warp.

John

Thanks very much for all the very valuable suggestions. I see where I can make a number of improvements in how I go about things.
Robert

Quote:

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Originally Posted by Robert M Richardson

Thanks very much for all the very valuable suggestions. I see where I can make a number of improvements in how I go about things.
Robert

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Learning from out mistakes is how most of us got to our current skill level.

That's why it's called woodworking and not just building stuff.

This is not a trade to learn from your mistakes. Do you see all the discussions on fingers missing and sawstop. Its a fools thought pattern to believe you learn from mistakes. Projects are one thing fail all you want but not being taught is cause of most of this. Even after proper teaching, there is did you listen to what you were taught, is there a huge pressure on a deadline and and no gaurantees. And dont forget Murphy.

Here is another movie star cutting plywood, you can see its walked off the fence. If you dont even know how to feed material why are showing people the wrong way to do it.


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I try not to buy 13/16" S2S material. Even if it is flat across the board it can have a twist or bow in it. When you cut it into smaller pieces, it will move, releasing internal stresses. True 4/4 rough lumber gives you plenty to work with. If necessary use your planer with a planer sled.. Brian