Waiting time to acclimate

[millwab]

Scrollers,
I'm helping a friend with a project and need some advice. She's cutting an approx 24" piece out of the middle of an 8 foot board of 15" wide oak. I don't know what kind of internal stresses might be in play in a piece like this, so I suggested that she let it sit for at least a day before doing anything with it in case the wood decides to move. Is 24 hours enough time? (As far as I know the piece is well dried and already planed down to 3/4") Please advise.

Bruce

[Bill Wilson]

Oak is generally pretty stable, but any tree is subject to growth patterns and circumstances that can cause internal stress in an otherwise nice, straight grained board. You are right to give this some consideration.

First, acclimation won't do a whole lot to prevent any severe internal stress release. If the tree was subjected to anything really drastic while growing, it could react badly as soon as it's cut, regardless of how dry and acclimated it is. Generally this will occur during a ripping operation.

Depending on where the board was before it went into the shop and how different the temp & humidity was, it may take up to a week. If it came from damp conditions, it should be laid flat, stickered to allow air circulation, and have some weight placed on top to hold it flat as much as possible. If the change in conditions wasn't drastic (from a dry storage location to a dry shop), then a couple days would probably be safe. Has it shown any tendency to cup or twist since it's been in the shop? Sometimes wood will begin to release when it's planed. If it is already planed and hasn't moved, then that is a good sign.

Good luck.

[workin for wood]

Bill hit it right on the head, and two weeks is pretty much the standard on acclimation time. Stress inside the wood is caused by two things, kiln procedure and logging procedure. We all know that wood has to be dried under specific conditions in a kiln, but alot of people don't know that the way a tree is cut down and even the way it grows, causes stresses. A tree that grows out of a hill for example, and then bends itself to reach for the heavens is a stress prone tree, but a tree on a hill that has no bend is safe. Tree branches are also under more stress. Cutting a tree too low to the ground...cutting at the knees as they say...makes the bottom part of the log more stressed than the rest. If you cut down a tree incorectly, like you cut all around it and then into the middle, then the tree will fall and the center of the tree will have spikey looking fractures coming out of it. This causes the heart of the tree to pull, which is a bad log. Of course, when you buy lumber, you don't know where it came from, or how it was dried.
Always try and rip it a little wider than you need, then use a jointer to straight edge the new boards and re-rip to the width you want. The splitter that comes with your table saw is there to prevent stressed boards from squeezing together behind the blade, causing a dangerous kickback...so don't through that device away.

[millwab]

Thanx guys. Ripping wasn't an issue because she wanted/needed the full width for this project. I was worried that after crosscutting a piece out of the middle it might move some. Talked to her this morning and found out that the whole board had been in the shop for months and looking at the cut piece 36 hours after crosscutting it was still flat. I think it's a go!

Bruce

[minowevie]

this is a wonderfull thread. and you have already answered some quistions i have had. please don't give it up know. for i would love to learn more on this . I have lots of problems. on my wood warping, and cuping. I never knew that about how the tree was cut down. Wow now this is enteresting. I would like to hear more on the cutting down thing. thanks Evie

[workin for wood]

ok...wood cups because of how it is cut from the log. If you take a log and cut it into quarters, so the end of the log looks like a 4 slice pizza, then you lay those slices out and resaw them, you have quarter sawn lumber. This lumber is the most stable because the grain is straight and consistent.
When you take a log and slice it all straight through..you have mostly flat sawn lumber, but you will still have some quarter sawn in the batch too. You can tell what the cut is by looking at the end of your board. when the grain is up and down consistently, it is quarter sawn. When the grain smiles/frowns at you it is flat sawn. Flat sawn lumber will always cup. If the grain is a smile, the cup will actually turn into a smile, so now you which way the cup will happen. When you lay boards on a deck, all the boards should be in a frowning position. This way the center may lift a bit, but not the edges, which would cause you to trip. btw...flat sawn cups during the drying process, once thoroughly dry the cupping will stop..that is why boards are cut extra thick at the mill, so that once the boards are kiln dried, the cup can be planed out.
Pine does not follow the same rules as hardwoods. Hardwood lumber is to be sold between 6-8 percent moisture, where as pine can be sold 8-15 percent moisture. Therefore if you buy dry lumber, pine is not necessarily dry, but hardwoods should be.
A Warp is the same as a bow..which would also resemble a bow and arrow. Usually this is caused by incorrect stacking while the wood is wet, but it can also be caused by a stressed board.
A twist is caused by stress. It can be because the tree was logged incorrectly, could be a bad part of the tree, or an unstable type of lumber. Most domestic lumber is pretty stable, so a twist was caused by using a bad log in most cases. With some other lumbers, such as apple, the twist is simply because the wood is naturally unstable. I use a lot of apple..when it is thoroughly dry, it has to be face jointed to take out the twist. I cut it fresh extra thick to make up for this problem.
When buying wet lumber, sticker the lumber every 2 feet with one inch stickers (wood spacers), then put weights on top such as cinder blocks. The pile must be on a level surface and has to be re-stacked at least every 30 days...the most movement happens when the lumber is closest to being dry.
and paint the ends of your boards to prevent moisture from leaving the end of the boards..this is what causes end cracks...moisture always leaves the endgrain faster than the face of a board.

perhaps this helps answer some questions.

[minowevie]

Jeff thank you so much. I have read some of this before. but you have put in a way, i am sure to understand. dang I wish i could copy this. I wonder, why does plywood warp so much. I would guess it would be for the same reasons. but mmmmmmmmmmm, not sure. do you have any advice on plywoods warping. thanks. we are so blessed to have you on this forum. Evie

[workin for wood]

generally plywood is a pretty stable product. If it is warping, its likely the way it is stacked or too much humidity. Otherwise, I have no idea.