pdovy

warped cherry after milling

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I've had a nice piece of 4/4 cherry sitting in the shop for the past two months waiting to be made into a six-pack holder for a christmas gift.  I finally got around to it this past weekend, cut up the four sides and milled them and left them flat on my bench for a few days while I futzed around making a box joint jig.  Lo and behold, the longer two pieces (only 11") have a noticeable cup when laid flat - I think it's minor enough to still work, but it makes me think I'm doing something wrong.

 

What's the best practice for keeping things stable?  Should I be rough cutting the pieces and letting them sit before milling them?  Cutting joinery ASAP after milling?  Crossing my fingers?  My shop is in a dry, heated basement and I had stored the rough board in the shop, so there shouldn't have been any moisture changes post-milling.

 

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I second What Particle Board said, and have a question to ask. How thin did you mill the stock to, and did you remove equal amount amounts of material from both faces? 

 

In my opinion, you really don't want to remove more than 1/8" of material from 4/4 stock without a 24-48 hour rest period. The rest period lets the wood equalize it's internal stresses. Removing equal amounts from both faces help minimize the difference in moisture content form one face to another, and thus possibility for movement.

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I second What Particle Board said, and have a question to ask. How thin did you mill the stock to, and did you remove equal amount amounts of material from both faces? 

 

In my opinion, you really don't want to remove more than 1/8" of material from 4/4 stock without a 24-48 hour rest period. The rest period lets the wood equalize it's internal stresses. Removing equal amounts from both faces help minimize the difference in moisture content form one face to another, and thus possibility for movement.

 

1/8 is pushing "rules" a little to far I would have been out of business years ago if I had to wait for my wood to have a two day hiatus.    You don't want to resaw 8/4 into 4/4 and mill to 3/4 right away. But to take 5/4 to 4/4 or 3/4 something along those line is just fine.

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==> you really don't want to remove more than 1/8" of material from 4/4 stock without a 24-48 hour rest period

 

I usually have the stock in the shop for at least two weeks prior to processing -- usually a month or two...

 

I usually process sticks in two stages, rough mill and final mill:

 

Rough: leaves the component 6" long (snipe) and a little heavy (about 1/4") on width & thickness to account for any movement overnight. I do try to remove even amounts from both sides of the stock... If the stock was squirrelly on the TS, I leave closer to 3/8" or even the occasional 1/2" (if the stock is case hardened) to account for movement.  

 

Final: process to final dimensions leaving thickness just slightly heavy... I then run it though the wide-belt for final thickness...  or if it's a panel, glue-it-up and run it through the wide-belt..

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This probably goes without saying, but I try to buy stuff that is pretty flat to begin with.  If a board is really cupped or twisted when it is rough I just assume it going to end up that way anyhow.  

 

If I am paying retail prices I make sure the boards are flat.  If I am buying stuff super cheap direct from the mill I don't worry about it too much, I just figure more waste and the guy I buy from tends to undercharge anyhow and his quality is consistent.   

 

I do store my milled stock either vertically or stickered.  The stickering is not really because of moisture, I just don't like laying it flat on a shelf or bench that might have a screw sitting on it or a sharp wood chip or anything that could knick up the face, but I guess it also helps keep the humidity balanced. 

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Regarding not laying it out on the bench - I hadn't heard of that - should I leave it stickered?  I guess it makes sense that the moisture content might become uneven if one side is open to the air and the other isn't.

 

It was S3S but at least from my hardwood dealer that only means its fairly flat, still requires milling to be dead flat, but I only took off a little more than 1/8".  I didn't pay attention to which side got the most treatment but I'll keep that in mind in the future.

 

Given that I have to mill it anyway I'd rather buy rough lumber, but I haven't found anywhere in the Chicago area that sells that way.  Thanks for the tips guys!

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1/8 is pushing "rules" a little to far I would have been out of business years ago if I had to wait for my wood to have a two day hiatus.    You don't want to resaw 8/4 into 4/4 and mill to 3/4 right away. But to take 5/4 to 4/4 or 3/4 something along those line is just fine.

it's just my opinion, and I think a safe bet for beginners who don't know what will work for a given species and board size. If you're a pro or a semi-pro you most likely already know how to gauge what's safe, and what's iffy.

 

Regarding not laying it out on the bench - I hadn't heard of that - should I leave it stickered?

you could sticker it, or just stand it on an edge. The main thing to keep in mind, is that when you mill stock it is going to move. How much to allow for is something you learn over time.

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For something small like that I leave it sitting on the table saw fence, if I think of it.  You do what you can as far as trying to prevent it but sometimes you gotta do what you gotta do or you do everything right and the wood has other plans.

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Skim plane rough lumber a few days prior to milling, this opens your wood and you can figure out what boards you are going to use for what. Then do your final milling. If after you mill your stock and it stays flat then moves on you a day or two later. Its just dryer on one side than the other.  Put your cut stock in plastic garbage bag and lay it flat. Let the wood equalize inside the bag, it should go back to flat.

 

If the wood moves after milling chances are its stress in the wood and not much you can do about that but process it out.

 

If your doing any work such as raised panels or something you lock in. Plan on doing that whole process that day. Don't give the wood a chance to move on you.

 

That's me and how I roll!  ;)

 

-Ace-

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Your over looking a very important step !!!

You said you had the cherry in your shop for 2 months. How did you store it ?? Did you leave it flat on the ground, leaning on a wall or on top of a pile of other boards ???

If your not using your wood straight away wether you buy it finished or rough the best way to store it is horizontal and stickered which allowed for proper air circulation and and it eliminates the chances of the piece bowing which is what would happen if you leaned the piece against

I'd guess your problem was caused from leaving the pieces flat without air circulation. The only quick fix solutions I have for that is wetting the cupped side but only slightly and allowing the piece to reacclimatize and hopefully straighten or as was stated already place in a plastic bag for a few days.

There is a lot of great advice in these answers you have already received and the only thing I can add is....

When considering the internal stresses of timber (which in most cases is caused by case hardening, where the outside of the planks and the centers of the planks have a varying moisture content), I find you don't really have to worry as much when it comes to 1" stock or 3/4" which is what I think 4/4 S3S is finished to because if the wood is stored correctly it will acclimatize very quickly because it's not that thick, if the air is allowed circulate properly and unless the plank has been taken from a very wet climate like an open shed into a dry one like a warm workshop then the piece should be very stable.

Also I only get 2 days a week in my shop so almost all my projects get time to acclimatize and they move from week to week and if I get a week off and I start and finish a project in the week guess what ??? It still moves. The most important things are knowing where your wood came from ( an open barn or straight from the kiln ) and storing it correctly.

Also keep in mind just because the pice has acclimatized to your workshop it doesn't mean it's going to be acclimatized to its final resting place. My shop isn't heated but it's insulated, I'd say it probably gets up to 10% moisture in there and when my pieces go to a nice warm house at around 8% moisture it's going to move. Just keep your joinery tight and allow for movement whenever and wherever possible.

Please don't be scared or discouraged by anything I have said just remember no matter what WOOD WILL MOVE !!

Happy woodworking :)

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Just don't lean it up against a wall to avoid having it flat, because then it can warp from being leaned up against the wall too.  Don't ask how I know this. :-)    

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I don't have a lot of experience with cherry, but it does seem to warp a lot. Is that the nature of cherry, or is just the stuff I've got that's warped, even though I stickered it properly?

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Thanks guys, all did turn out well eventually.  The warped pieces where short enough and the warp minor enough that it didn't effect the joinery and wasn't noticeable in the final product - I mostly just wanted to learn from my mistake so I don't have this problem in the future in some situation where it is a real headache.

 

I did unfortunately just leave the unmilled board leaning against my wall.  I've learned my lesson - my latest lumber purchase is sitting horizontal and stickered!

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