How long to let lumber "relax" after the initial milling before final dimensioning?

[kooshball]

Out of curiosity, how long do you folks let your lumber sit after the initial milling? I have been milling mine just to the point where the lumber is smooth (usually ends up ~1/8" over final thickness) then letting it sit for a week before re-flattening, squaring and milling to the final thickness.

I don't want to rush things and mess up my project but with the long weekend it is tempting to just let it sit overnight before taking it to the final dimension and doing the joinery.

In this case the lumber is walnut and poplar.

Thanks

 

[Trent Mason]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

David,

Is this green lumber? (Just milled from a newly fallen tree) If that is the case, it could take months depending on the thickness/width. If it is already dry then you shouldn't need to wait at all. :eusa_thin

I've never milled green lumber for anything more than a small turning, but even a bowl that is turned out of green lumber needs to be coated with Anchor Seal and left to dry for 3+ months. Then put it back on the lathe and true it up. If you're talking about green boards, you probably want to sticker them and let them dry before using them. Hopefully one of the sawyers will respond soon with more specific answers.

 

[Bas]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

I assume the lumber was previously dried (air or kiln). It all depends on how much you took off in the milling process, and how much time the wood had to acclimate in the shop. If it's 4/4 material that was stacked in the corner for couple of months, I doubt you need any kind of rest period. But if it's 8/4 material that's only been in the shop for two weeks, you may need the additional rest time. It also depends on how stable the material is. Walnut and Poplar should do better than most.

 

[kooshball]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

Sorry, I should have clarified that the lumber is all kiln dried and well below 10% on moisture content.

It all started off as 4/4 rough and will end up at 3/4". All the lumber has been stickered and stored in my garage for a few days (weeks for the walnut).

Thanks

 

[Bill Clemmons]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

When I bring wood into the shop for a project I usually let it adjust for about two weeks before doing anything to it. After that I haven't had any problems w/ changes after milling. Most of my wood is rough and stacked in a shed outside my shop, w/ no climate control.

HTH

Bill

 

[robliles]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

If you don't have a lumber moisture meter, get one. If you don't have a thermometer and relative humidity guage on your shop wall, get one. Download the chart from Fine Woodworking that shows stable moisture content at various temperatures/relative humidity levels and use it. I like what you are doing by dressing down to about 1/8" a letting the wood "rest". I do this with all the lumber I use, first by bringing it into the shop as far ahead of time as possible, and then letting it stabilize. Thickness is important. 4/4 will stabilize fairly quickly, 8/4 takes a couple to four weeks, 16/4 needs a month or more if possible. This is assuming that the moisture content of the wood to begin with is relatively close to stable. I keep all my lumber in an open air shed and the moisture content stays around 10% to 12% depending on the time of year. My shop is humidity controled and I need lumber to be around 8% or 9% to be moisture "stable" Dressing lumber can also release stresses in the lumber not affected by moisture and dressing down to about 1/8" of the final thickness will really help release these stresses. You are wise to let your lumber "relax" before using it in a project.

 

[kooshball]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

If you don't have a lumber moisture meter, get one. If you don't have a thermometer and relative humidity guage on your shop wall, get one. Download the chart from Fine Woodworking that shows stable moisture content at various temperatures/relative humidity levels and use it. I like what you are doing by dressing down to about 1/8" a letting the wood "rest". I do this with all the lumber I use, first by bringing it into the shop as far ahead of time as possible, and then letting it stabilize. Thickness is important. 4/4 will stabilize fairly quickly, 8/4 takes a couple to four weeks, 16/4 needs a month or more if possible. This is assuming that the moisture content of the wood to begin with is relatively close to stable. I keep all my lumber in an open air shed and the moisture content stays around 10% to 12% depending on the time of year. My shop is humidity controled and I need lumber to be around 8% or 9% to be moisture "stable" Dressing lumber can also release stresses in the lumber not affected by moisture and dressing down to about 1/8" of the final thickness will really help release these stresses. You are wise to let your lumber "relax" before using it in a project.

I stand corrected. I just took some moisture readings and found the walnut to be 9-10% (which is the same as the walnut furniture in my house so I am good there) but the poplar is between 9.5-12%. I looked at the chart on FWW but it is not organised by species; I wonder if certain types of lumber have more of an affinity for moisture pickup?

Thanks

 

[scsmith42]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

If you don't have a lumber moisture meter, get one. If you don't have a thermometer and relative humidity guage on your shop wall, get one. Download the chart from Fine Woodworking that shows stable moisture content at various temperatures/relative humidity levels and use it. I like what you are doing by dressing down to about 1/8" a letting the wood "rest". I do this with all the lumber I use, first by bringing it into the shop as far ahead of time as possible, and then letting it stabilize. Thickness is important. 4/4 will stabilize fairly quickly, 8/4 takes a couple to four weeks, 16/4 needs a month or more if possible. This is assuming that the moisture content of the wood to begin with is relatively close to stable. I keep all my lumber in an open air shed and the moisture content stays around 10% to 12% depending on the time of year. My shop is humidity controled and I need lumber to be around 8% or 9% to be moisture "stable" Dressing lumber can also release stresses in the lumber not affected by moisture and dressing down to about 1/8" of the final thickness will really help release these stresses. You are wise to let your lumber "relax" before using it in a project.

Great post, and spot on.

Yes, poplar will pick up moisture more quickly than walnut. It will also lose moisture more quickly.

One important thing is to be sure to remove about the same amount of material from each side of your board. As a board picks up moisture after it comes out of the kiln, it does not permeate all of the way through right away, and thus the moisture content may be different at 1/64" depth versus 1/16" depth, versus 1/8", etc, especially when it has been exposed to significant recent swings in humidity.

When milling from 4/4 down to 3/4, if you mill 1/16" off of one side the board, and 3/16" off of the other side, this is when you will usually see some movement in the days after milling. However, if you can remove approximately the same amount from each side, the board will ususally remain more stable.

Be sure to sticker your lumber after milling as you're waiting for it to equalize.

 

[Glennbear]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

Great post, and spot on.

Yes, poplar will pick up moisture more quickly than walnut. It will also lose moisture more quickly.

One important thing is to be sure to remove about the same amount of material from each side of your board. As a board picks up moisture after it comes out of the kiln, it does not permeate all of the way through right away, and thus the moisture content may be different at 1/64" depth versus 1/16" depth, versus 1/8", etc, especially when it has been exposed to significant recent swings in humidity.

When milling from 4/4 down to 3/4, if you mill 1/16" off of one side the board, and 3/16" off of the other side, this is when you will usually see some movement in the days after milling. However, if you can remove approximately the same amount from each side, the board will ususally remain more stable.

Be sure to sticker your lumber after milling as you're waiting for it to equalize.

In other words, do not leave your boards laying on the bench without an air gap underneath or nasty warpage can occur. DAMHIKT :BangHead:

 

[FredP]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

lumber never gets to relax in my shop!:rotflm:it only gets short rests between machines.:gar-La;

 

[cpowell]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

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In other words, do not leave your boards laying on the bench without an air gap underneath or nasty warpage can occur. DAMHIKT :BangHead:

I've found out the same thing - the hard way. Sticker with air gap = great idea. :gar-Bi

If it doesn't move (bow, warp, twist) in a day it's not going to move.

Walnut is pretty stable. If it's straight grained it behaves pretty well.


Chuck

 

[klfelkins]

Re: How long to let lumber "relax" after the initial milling before final dimensionin

After our lumber reaches 10 % we let it set in our shop for 2-4 weeks (depending on the wood) so it has plenty of time adjusting to the moisture level.