Milling lumber correctly.............warping, bowing, etc.

[Jim Fox]

Long time lurker, have posted, but not very active........because I get frustrated and don't go back into the shop for months and months.

Need some input on best milling practices as I always seem to struggle with boards warping/twisting/whatever days after milling. So after milling up boards with the jointer and planer, things look great. Boards lay flat, no wobble, glue seams nice and straight. But a day later, 2 days, 5 days, etc.............it all goes wonky. Wobbling, cupping, bows. So I always, say with a 3/4 finish, rough mill to like 7/8 or so. Let that sit for several days and then finish mill...........and I still get the issue.

All my boards are kiln dried. Boards are all stored in the basement of a 3 season porch, which has a double door entry to the outside world. No climate control in that room, but it is a dry cool room. Shop is in the basement of the house with heat and A/C. A/C doesn't run constantly, only when it's muggy/hot. Right now it's winter (if you want to call it that), so the humidity in the house and wood storage are close. Ok, I just checked...........the basement of the porch is higher than I thought. Wood storage is at 47% this morning. The shop is at 34% and the Nest thermostat for the house says 32%.

So this past weekend I milled up 4 walnut boards, 1/2 x 6 x 14.5. Noticed last night that at least one of the boards was now cupped. This is pretty common.........a little cupping, or a wobble or a bow on skinnier boards. So obviously I am doing something wrong.

So annoyed............always makes me want to stay outta the shop or toss it all in the yard and set it on fire.

Thanks!!!!! (we'll delve into other issues later)

Jim

[John TenEyck]

The moisture imbalance from storage to your shop is what's causing at least some and probably most of your problems. Bring your wood into your shop a couple of weeks before you want to use it and your problems will be far fewer. After you mill your wood do not lay it flat on a bench; rather, lean it against a well, etc. so that air can freely circulate around it. And don't wait between milling and using the wood. If you want to mill it oversize and let it sit a day or two, fine, though I almost never do, but after you mill it to final dimensions cut the joinery and glue it up into your project as soon as possible. If you can't, lean it against the wall, etc. so air can circulate around it. If there is no moisture imbalance there will be no movement so work to minimize any imbalance.

John

[Richard Coers]

One of the issues trying to acclimate the wood to your shop is having complete air flow around the wood. If you flat stack it after milling, or let a board sit on the bench, air only gets to one side of the top board, and then not the others. The top board will cup. Add stickers between the boards to allow full air flow.

[Paul F Franklin]

I agree with John that allowing the boards to acclimate in your shop will likely solve or greatly reduce the issue. Using the parts right away is good advice, but is often not practical with the workflow I use. On larger projects, I sticker dimensioned parts until I can use them. On smaller projects, I often place them in a trash bag (folded closed afterwards) after final milling if I can't assemble them right away. Stickering the parts promotes even air flow and moisture exchange. Placing them in a bag minimizes air flow and moisture exchange. Either way helps minimize post-milling movement.

[Jim Fox]

The moisture imbalance from storage to your shop is what's causing at least some and probably most of your problems. Bring your wood into your shop a couple of weeks before you want to use it and your problems will be far fewer. After you mill your wood do not lay it flat on a bench; rather, lean it against a well, etc. so that air can freely circulate around it. And don't wait between milling and using the wood. If you want to mill it oversize and let it sit a day or two, fine, though I almost never do, but after you mill it to final dimensions cut the joinery and glue it up into your project as soon as possible. If you can't, lean it against the wall, etc. so air can circulate around it. If there is no moisture imbalance there will be no movement so work to minimize any imbalance.

John

See I always tried to avoid leaning it against the wall. To me that would add the possibility of inducing an arch (lack of a better term) across the length of the board (like a bridge arches)


One of the issues trying to acclimate the wood to your shop is having complete air flow around the wood. If you flat stack it after milling, or let a board sit on the bench, air only gets to one side of the top board, and then not the others. The top board will cup. Add stickers between the boards to allow full air flow.

That's what I always try to do, add stickers between each board if I do that.




I'll let them sit longer in the shop before using them the next time.

[Cliff Polubinsky]

Jim,

You're probably aware of this but for those who aren't, always mill equally from both sides. Milling unequally can result in a moisture difference between the sides and will cause warping. Sometimes if you leave the warped board sit and sticker it so air gets to both sides the board will straighten out.

Cliff

[Prashun Patel]

Great comments so far. I echo: Let boards sit in your shop for a few days. Mill equal amounts from either side. Mulling over a couple days like you do is good.

Straighter grain and quartersawn boards will improve results too.

[Gordon Dale]

I agree with John that allowing the boards to acclimate in your shop will likely solve or greatly reduce the issue. Using the parts right away is good advice, but is often not practical with the workflow I use. On larger projects, I sticker dimensioned parts until I can use them. On smaller projects, I often place them in a trash bag (folded closed afterwards) after final milling if I can't assemble them right away. Stickering the parts promotes even air flow and moisture exchange. Placing them in a bag minimizes air flow and moisture exchange. Either way helps minimize post-milling movement.

Thanks Paul for adding this. The (good) advice to use the wood as soon as possible after milling brought to mind the question of what to do if you can't use the wood right away or want to batch-mill a number of boards.

[Jim Andrew]

You probably need a dehumidifier in your storage room. I used to have problems like you describe, and built a solar wood drier, using a 48' insulated container with solar panels, and a blower to circulate the warm air. Did put a dehumidifier inside to remove moisture. Now when I get some lumber, can plane it right away and have no wood movement.

[Brian Tymchak]

Even if lumber has been sitting in my shop on the racks for months, I still rough mill, sticker, final mill, and sticker sgain if I can't use it right away. There is moisture differential in a board from surface to core, unless maybe the board has been in the shop for years. But even then I would still mill/sticker/mill, just in case.

[Alex Zeller]

At my old shop the cement slab would play havoc with wood. It seamed like some days it was colder than normal and suck the humidity down near the floor. I ended up putting one of those box fans on low to help promote good air movement. I also built a wall mounted rack. Between those two thinks and stickers/ gaps it went a long way towards not dealing with moving wood. It does get frustrating when you think you've made perfectly flat boards and the next day you go to glue it up and wonder what happened.

[Mel Fulks]

I always cut off the convex side when facing. It will often make the whole board move to straight. It often works and
NEVER makes the problem worse. After planing the other side, any wood thickness that needs to go should be removed
from the currently convex side ( it can change as you work). I perceive you are wondering "if that 's true ..,.why haven't
I heard that before? Fear of LIABILITY
This post applies ONLY to bow. NOT cupping

[Patrick Kane]

I think everyone covered the problem. 1) how much "wobble" are we talking? 1/16" over 4'? More? 2) do you own a moisture meter? I think you need to own one in your current situation. Frankly, i think we all need to own a decent quality one.

In my experience, if i do not sticker parts and leave them for a week in my shop, its not unusual to come back to a slight movement--say, 1/16" over 6-8'. Like you, glue joints that were absolutely laser perfect last week now have a tiny gap in the middle. Nothing that clamps cant fix, but still. Like others, i really try to leave parts in the rough as long as i can. Tops are an example of this. I will NOT joint and plane boards for a table top unless i have enough time to glue them up that day and have finish on them in the next few days. As an example, if its 1pm on a Sunday and i have 3-4 hours of shop time left, i will not start milling table top boards. Those boards would make it into a panel and sit unfinished for a week+ and develop some level of cup.

[Ron Citerone]

Acclimate! The longer the better. Milling a little off each face and then letting it acclimate a little more has helped me out. If you are ripping a wide board for stiles and rails, rip them an 1/8” wide after the first face planing so they acclimate before final ripping. If you got the time I think it’s worth it. If time is money, well, you may not have the flexsbility.

[Kevin Jenness]

One thing you want to avoid is leaving one face of a board exposed to the air and the other covered. To keep boards from moving between sessions you can dead stack the pieces (stack them tight on a flat surface) and cover them. Overnight you can get away with a blanket or a piece of ply, for longer periods wrap in plastic to keep the endgrain from picking up or losing moisture. As said, it's best to get the wood into the shop several weeks prior to milling for acclimation.

A moisture meter is convenient but not critical if you are controlling the shop atmosphere and acclimating the wood. I mostly use a meter when buying in lumber. When I am using lumber from storage I try to plan ahead so time is on my side.

[Derek Cohen]

Jim, in addition to ensuring that the boards are dry enough and given time to acclimatize in your workshop for a time (I give it a minimum of a few weeks), after preparing the boards, and when they are not in use (such as over night when the temperatures drop), I sticker and clamp all boards ...

https://i.postimg.cc/zX6z3VFS/Entry-Hall-Table-For-ANiece1-html-m67e76846.jpg

https://i.postimg.cc/bNsYzQkw/Entry-Hall-Table-For-ANiece1-html-2a49e29a.jpg

Regards from Perth

Derek

[Bruce King]

Jim,
All good advice so far but you should get some African Mahogany, it’s very easy to work and more stable than typical woods. I used to have an unconditioned shop and never had an issue with it there either. Don’t let the price scare you away because it’s about the same as many other woods after you figure in the all the bad sections of other woods that mahogany does not have.

[Rob Damon]

I also clamp freshly milled boards heavily, mostly because it may take a week or two to get back to them. Never had issues.
447359

447360

I also use a lot of stretch wrap for similar scraps for future use (rails).
447361

[Mel Fulks]

Bruce, you have been real lucky with African mahogany. I've had to use it a number of times and found it to be no
where near as stable as the real mahogany. In keeping hours on a number of jobs using each I saw the additional time to
work it ,and it's instability eat up all the "saved" money ,and more. I changed a number of management minds by
demonstrating , and inviting them to do their own tests.

[Mel Fulks]

Acclimating is good ....on your own projects. Telling a client you are waiting for his material to acclimate can put you
out in the cold. I always ,even as an employee, demanded "at least 24 hours in warm shop or it might all fall apart". Occasionally
circumstances would give me more time than the one day.

[Mel Fulks]

When you don't acclimate before gluing, you might see all the glued up stuff you left leaning against the wall ....on the
floor with the clamps off. A real mess. Always funny to see new green guys demanding to know who messed up their
work.

[Jim Fox]

I think everyone covered the problem. 1) how much "wobble" are we talking? 1/16" over 4'? More? 2) do you own a moisture meter? I think you need to own one in your current situation. Frankly, i think we all need to own a decent quality one.

In my experience, if i do not sticker parts and leave them for a week in my shop, its not unusual to come back to a slight movement--say, 1/16" over 6-8'. Like you, glue joints that were absolutely laser perfect last week now have a tiny gap in the middle. Nothing that clamps cant fix, but still. Like others, i really try to leave parts in the rough as long as i can. Tops are an example of this. I will NOT joint and plane boards for a table top unless i have enough time to glue them up that day and have finish on them in the next few days. As an example, if its 1pm on a Sunday and i have 3-4 hours of shop time left, i will not start milling table top boards. Those boards would make it into a panel and sit unfinished for a week+ and develop some level of cup.

I do not own a moisture meter. This was probably a 1/16 of wobble over a 6" x 14.5" board.

[Justin Rapp]

Jim, in addition to ensuring that the boards are dry enough and given time to acclimatize in your workshop for a time (I give it a minimum of a few weeks), after preparing the boards, and when they are not in use (such as over night when the temperatures drop), I sticker and clamp all boards ...

https://i.postimg.cc/zX6z3VFS/Entry-Hall-Table-For-ANiece1-html-m67e76846.jpg

https://i.postimg.cc/bNsYzQkw/Entry-Hall-Table-For-ANiece1-html-2a49e29a.jpg

Regards from Perth

Derek


Derek,

That wood is amazing, what is it?

[Prashun Patel]

You can do a lot to minimize the criticality of long acclimatization times and excessive clamping by how you pick your grain.

Learning to read grain both on the face and side and end, and getting comfortable with the aesthetics of straight grained wood (and the associated costs of waste to obtain it, will go miles to long term stability.

On some level, wood movement is an expression of the woods true nature. If you manage to tame a wild board long enough to get it into its bound and built form, there's no guarantee it will stay that way. But you really minimize this risk by picking things that don't WANT to move so much.

[Derek Cohen]

Derek,

That wood is amazing, what is it?

Justin, that wood is wonderful, I agree. Fiddleback Jarrah.

Very hard, interlocked, and sometimes not fun to work with as it can be brittle. But when it comes out like this ..... :)

https://i.postimg.cc/KvTc4xvN/4a.jpg

The other end ...

https://i.postimg.cc/T1zRQHQg/5a.jpg

Regards from Perth

Derek

[Bob Cooper]

Not to be too contrarian here but I’d say acclimate it before you mill it but once you do I would not sticker it or encourage air circulation. I’d wrap it up tightly in plastic to keep all flow of air away from it until you can assemble it.

[Justin Rapp]

Not to be too contrarian here but I’d say acclimate it before you mill it but once you do I would not sticker it or encourage air circulation. I’d wrap it up tightly in plastic to keep all flow of air away from it until you can assemble it.

A lot of this also depends on how much you need to take off the wood and how long the wood's been acclimating. I just finished a project where I was using kiln dry wood that was in my very dry workshop for about 1 year, stack and stickered even though it was dry already. The wood was 7/8 and after cutting parts down to size, I took 1/16 off each side on the jointer than planer to have 3/4 parts. I labeled the parts and stacked them on my workbench and slowly over the course of weeks took parts i needed for each part of the assembly. Nothing warped.

For the OP, moving the wood into the shop for a few weeks first as others said, but also, than milling the wood down to just over the thickness and width, and let it sit again for a few weeks before milling and cutting the parts followed by assembly. This would greatly help ensure any wood movement between the steps has time to be corrected.

Also I think the moisture of his storage area being 47% is pretty high compared to the 34% he had in his workshop. This change might require an even longer sit time.

[Justin Rapp]

Derek - seems that wood is hard to get - almost impossible here in the usa. Your right that stuff is hard, 1910.... I've worked with a good amount of hickory which is 1820 and it eats blades....