Ok, so I’ve been “serious” about woodworking for a couple years now. This means that I finally got all the equipment to mill stock, invested in a cabinet saw, learned about proper joinery methods, etc.
The thing that has vexed me far beyond any other issue is the one I can’t seem to control and that’s wood warping. Specifically, what wood does after it’s been re-sawn, or some times even ripped or cross-cut.
The classic example is the Brazilian cherry i used for the front legs on a cabinet I recently finished. Milled the 7/8 x 6 x 40 piece from some 5/4 rough cut stock so it was dead flat. This is the front edge of the two mitered front legs with a connection between them that forms the molding around the bottom edge of the carcass. Marked out the curved legs and cut out the waste on the band saw, leaving the top edge of the leg piece about 1 1/2″ tall for most of the distance. Well, once that waste was removed the legs board twisted because of some tension in the wood. Fortunately, I was able to twist it back out since it was the front board but the same thing happened on the side leg boards and they didn’t pull back into perfect alignment so easily being only about 17″ long.
Another example was on the same project where I had a beautiful 8/4 timber that I milled down to 1/2″ x 6″ x 40″ boards to edge glue for a back panel. Every time I cut a slice off the timber (which started flat) the slice would warp, twist, bow or some times all three. There was so much tension in the wood that I had to cut the slices almost 3/4″ thick to be able to joint them back down to usable 1/2 (or even less). Then as I was trying to flatten the boards it was like chasing the end of a rainbow. I’d flatten one side on the jointer to remove the cup or twist, then after running it through the planer some of the warp would return, though not as much. Then joint again, plane again, less warp. It got to the point where I just had to decide how much I was willing to live with, because I’d end up with a piece of paper before I got all the tension out of the wood. This also seems to happen with Maple and American Cherry too, though not usually as bad.
Finally, there’s the case where you mill a piece and get it to proper size and it’s perfect. Set it aside for a few days and come back to a warped board. Ok, I know that’s supposed to happen a little, but what’s the best strategy to deal with it? Use stickings and stack them high so gravity holds them flat while they adjust? Then, assemble it quickly before it starts to warp? I’ve heard this suggested, much like storing finished pieces assembled dry so they don’t warp on you but it seems like that could come back to bit you years down the road.
I guess my question is all about how to avoid as much of this as possible. Am I not selecting “good” stock? Is it likely the wood is too wet/dry (i buy only from lumber yards that sell kiln dried stock)? Should I mill and assemble all in the same day? Should I expect to waste a log of wood milling and re-milling until the warp is gone?
I guess I’m just at my wits end in terms of how to avoid re-milling stock and I’m not sure what the real problem is.
Thanks in advance.
Replies
T,
Boy, I'm glad you've asked this. Let's see what the sages bring us.
I guess I've been seroius about woodworking for about three years now. My genereal feeling about the kind of movement that you are talking about is that you just have to let it happen. I'm a firm believer in the rough milling/final milling process. If you don't do it, you're hoping for something that just ain't going to happen. In cases where I don't let the wood relax for a few days after being close to final dimension, and then final mill it, I knowingly accept some 'warpage'. I think you have to choose your tolerance by part and by project. In a sculpted chair, don't worry about it. With shaker cabinet doors at least get the edges perfectly jointed (if not the faces) so they'll go together square. You know that wood moves. So don't fight it--learn it; and yes you do have to give up stock in the process. These are just my general feelings and are not necessarily targeted at you or anything. (I like to include that disclaimer a lot on Knots!)
Brian
Ok, I've been serious about wood for about 45 years now, 40 as a professional. What you are experiencing is poor lumber drying as near as I can tell. Tension from improper drying or post drying handling or storage will cause the problems you describe, but it most likely happened in the kiln. This is the bane of the hobbiest woodworker, with less than reliable wood sources, yet paying the highest prices.
Keep in mind some woods are just more likely to move on you- Jatoba (Brazilian Cherry, sic) being one of them. You can get a copy of Hoadley's book about wood technology and it will help you understand what is happening, but your lumber source is the root of the problems. Take some pieces back to them and show what is going on. They may not be aware, or they may not care - but at least you let them know.
Resawing is one of the fastest ways to find improperly dried lumber - casehardened is the usual defect. Case hardening is where there is MC differential from "shell" to core of the board. You can see where resawing would then accentuate the out of balance situation, and the resawn boards would start cupping and bowing.
I used to test a sample of newly arrived lumber by cross cutting into the center of a long board, crossing off a piece about 2" long (by 8/4 thick and say 9" wide. This was then taken to the bandsaw and turned so the end grain was on the table, and a deep "U" shape was cut into it from one edge. If the two legs of the "U" stayed parallel (about 8" long in this case), then we unloaded the truck. If not, we considered sending it back. Sometimes the sample would split on the bandsaw it had so much casehardening to it.
Take some samples to your vendor.
Dave S
http://www.acornwoodworks.com
a
I'm intriegued by your process for testing stock, thoguh I can't be sure I understand what you were describing as a process.
If you cut a 2" slice out of the middle of 8/4 stock, and put it end-grain down then you must be cutting a 9" long U that's 2" by 2". I guess it would would look a lot like one of those wooden salad tongs you buy for the kitchen if I'm understanding it correctly.
Am I understanding you right? It seems like a great way to test the internal tension. How thin do you cut the legs of that U shape to feel confident it's good stock?
Thanks.
Yes, it is hard to describe adequately. Your salad tong analogy is very good. The walls or legs are about 3/8" in 'thickness'. You don't have to be too fussy - these are always free handed on the bandsaw, with the bottom of the 'U' chewed out with repetitive cuts. You will see pretty quick if your material is casehardened or not. The difference between working properly dried material and improperly is like night and day. Drying lumber is a science - perhaps less than perfect science, but science nonetheless. If the material is not dried properly it is not the wood's fault. There is no reason why anyone should accept poorly dried lumber on a commercial basis. To do so is to accept the slide towards mediocrity that we all should be actively resisting. Dave S
http://www.acornwoodworks.com
TM ,
The fact is some species move more then others . When resawing ,the moisture content is no longer centered in each piece maybe except the one from the center if there is one . They seem to cup . When you don't have a good selection of extra boards to choose the right board for the right place it is tough .
When you have a edge curved board or a banana chances are it will always be a banana so if you need runners for a rocker or an arched board these are a good choice . Have you ever seen a stack of 2X4s fresh they look decent when you leave them and let them sit in the sun they may turn to pretzels but if you frame the wall right up and put your drywall or sheeting up they stay put much better , well the same is often true for some hardwoods as well . I may rip stock ahead of time stack it flat while still in 10' lengths keep it out of the sun , maybe a week before I mill it up for a set of doors , some movement will occur but generally I can cut around it and make it work.
regards dusty
"I guess I'm just at my wits end in terms of how to avoid re-milling stock and I'm not sure what the real problem is."
You can avoid many problems by buying seasoned rough sawn timber in standard thicknesses , like they do or did in furniture factories. This reduces waste and having to produce 1/2" thick boards from 8/4 stock which is a shame.
Wood moves, some species more than others, as already pointed out, but very often the movement seen after machining returns to normal or at least within acceptable/manageable proportions if the stock is set aside /stacked so that air can circulate as evenly as possible all round- especially if the timber is of higher grade and reasonably acclimatised.
If you use random "run of the mill" stuff with wild grain running out at the edges , tension, knots etc then there is going to be warping , twisting, cupping and the rest. So choice of timber and grade is important. Are you using stuff that has just come into your shop or is "wet" ?
If you live with wood you find that trying to work it like metal doesn't work very well . There are so many species all with definite characteristics-and no two pieces are exactly the same - which makes it interesting.
Dat's my sixpence worth.
I really wish I could find a supplier that had reliably dry stock.
Does anyone have a positive recommendation on the Peninsula in the (San Francisco) Bay Area? Global Wood Source has good material, but I'm looking for 5/4 cherry and they don't carry it.
Assuming you're buying roughsawn stock:
That said, also sounds like you've bought lumber with some drying defects.
Re-sawn stock will move a lot. You need to resaw with plenty of allowance for flattening. Set resawn stock aside for two weeks before final milling.
Edited 7/3/2008 9:42 am ET by TaunTonMacoute
All -
Thanks for the quick and valuable responses. I will be sure to start frequenting this site to take advantage of the expertise you all provide to those of us who are in the meat of the learning curve.
If I can sum up what I've heard so far it would look like this:
1) Wood that has been dried improperly, or stored poorly after it has been dried is the most likely and severe contributor to my issues.
2) Wood is after all wood and some movement is expected, more so from the more dense and wild grained species/pieces but this should be manageable if properly dried.
3) Selecting wood that has a more uniform grain pattern will help for pieces that need to be long and straight (like the 2" x 2" x 45" corner posts, or the 1/2" x 6" x 40" long back panel slats on that cabinet I just finished!).
4) If the wood has a certain curve to it when it's purchased, you should expect that to re-appear (at least a little) after it's been milled, since it's an indicator of the wood's internal tension.
5) Buying rough stock that's as close to your finish-milled dimensions is best, since the less wood you remove, the less the board will adjust.
All this seems to explain my experiences pretty well. For example, after building most of that Jatoba cabinet I needed one more piece that had a certain color/grain pattern to match another already finished. Well, none of the remaining rough stock i bought for the project really matched what I needed. So I was sifting through my scrap pile and noticed a 4/4 board I had bought already surfaced from my local WoodCraft store. It had been sitting in my garage (in Florida, mind you!) for about a year. It had the right color and grain so I held my breath and slapped it down on the cabinet saw to see if it was close enough to true that I might be able to use it. To my shock and awe it was almost dead flat. Very minimal flattening and it was probably the best board in the whole project to work with. The rough stock I purchased for the rest of the project was from a lumber yard that stores their wood outside under tarps in Florida humidity. I understand now that it had been out there for the better part of a year before I picked it up.
On my previous project, I used American Cherry from the same yard, but that stock rotates every month or so because it's a popular wood. It's also stored under an overhang and gets less direct moisture when the wind and rain blow. On that project (FWW Country Hutch project from the cover earlier this year) I milled almost every piece in the entire project in one week and had them all stacked under my workbench for a couple months as I finished up the project. Almost no issues with warp, expect for some wide (12")boards for the table top that ended up getting a LOT of hand-planing and eventually bread-board ends.
I guess it all comes down to the raw material, and careful planning. Yea, seems obvious to me now too...
One additional thing to keep in mind; it's been addressed indirectly in some of the previous posts: Resawing is about the most difficult test of good drying and uniform moisture content that there is. If the wood comes out straight after resawing, you can be confident that it's in good shape. That said, if it doesn't come out straight after resawing, it doesn't necessarily mean that you have a problem. It could mean that there is some transient moisture imbalance in the wood (e.g., it had been stored in a dry environment for two years, and then moved to a humid environment for the last month). This is why it is important to let the wood "rest" after cutting, and especially after resawing. You want to let it do it's thing to get an understanding of where it wants to go, so to speak.
-Steve
One thing some old timers explained to me might apply here, and I've found it to be true. Just stacking a pile of boards on the bench overnight will often leave you with the top pieces cupped or warped the next morning, the lower pieces being protected by the top pieces, which lose or gain enough moisture on their unprotected side to change shape. The solution is to never leave a stack uncovered, either with some junk wood or a chunk of ply big enough to completely cover the pile. This can be especially important when doing a job with a big cut list, as you can't afford too many culls, but it applies to the four aprons for a single table as well.
Stickers.
My experience has been much in favor of keeping parts stickered.
It often takes more time/work and sometimes more space but at least all sides of each piece are experiencing any/all fluctuations in conditions and thus have a better chance of remaining flat.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
In today's economy it is very difficult to find properly dried/well seasoned wood. It is too expensive for the supplier/retailer. Toyota developed just in time invetory delivery to squeeze out excess carrying costs. Wal-Mart took it up a notch and applied the concept to the entire retail delivery chain.
With costs rising and margins thin wood suppliers/retailers had to adapt or die. The wood they sell now can't be dry or well seasoned. The carrying costs are too high, and the volume is too low.
The end result is the wood worker pays the carrying costs. Buy lumber now. Depending on type, width, your location, where you store it, time of year, and a couple of other factors, it might take 3, 4, 12 or 18 months to dry.
The down side is you have to design, plan and buy well before you start cutting. The up side is you get to look a beautiful wood for a long time (unless SWMBO starts complaining that you work too slow).
There's a couple of other possibilities that haven't yet been mentioned:
1) You could have branch wood, or wood from a tree that was leaning or growing on a hill. Such wood will never stop moving, even when well dried and in a stable environment. Sooner or later, every woodworker runs across this stuff, and the best thing to do with it is cut it into small pieces and feed it to the wood stove. Potentially, you can make small projects out of it that don't require dimensional stability (like a small box), but building large pieces of furniture out of it is going to be extremely difficult.
2) Your shop humidity could be wildly fluctuating. I don't know how close to the ocean your location is, but San Francisco goes through wild swings in humidity daily, with fog in the morning (100% relative humidity), to warm and sunny in the afternoon (30% humidity). Unless you're a house carpenter, you can't do good work in an un-conditioned shop in this sort of environment. It would be very wise to install whatever you need (generally a combination of a dehumidifier and temperature control) to keep the relative humidity within +/- 5%, and stack and sticker your rough wood in that environment for at least 2 weeks before you work it.
Point #2 is really important. There will likely be others that chime in on this thread and insist that they build furniture all the time under wildly varying humidity conditions, but trust me, you will get far fewer gray hairs if you follow this advice. This is particularly true if you have a day job other than woodworking and you have to build a piece over a three week (or three month) period. This is my situation, and I can reliably plane and joint a board within 1/16" of its final dimension, stack and sticker it, and have it remain within those dimensions for a couple of months, largely because my shop humidity is pretty much constant at 50% r.h. during the summer, and 40% r.h. during the winter.
Others have addressed the cause of the problems you're experiencing. I'll add a few solutions to the one or two already mentioned.
First, if you're not going to assemble the cut pieces right away, sticker them, put some type of cover wood on the top, and put some weight on the cover wood. Cinder blocks are an easily managed and obtained source of weight. This is not too time consuming with furniture parts and doesn't require too many blocks.
Second, if you do get warping, try this trick. Wet the "inside" of the warp and set the board on a reliably flat surface. Let it dry. Minor warp can be corrected that way. I've corrected severely warped panels by wetting the inside of the warp and then clamping the panel to a flat surface, with the outside of the warp to the surface. This weekend, I took the warp out of two panels by wetting the inside and then clamping them together, outside to outside. Check your progress and continue to wet the inside of the warp until its gone. Of course, you should be checking once the board or panel had dried out. I haven't done this with anything like a table leg, but it works great for wide boards and panels.
I would even try the second suggestion on twist. May not work, but it won't hurt to try.
EDIT: Once the warping is gone, keep the lumber or panel clamped (or stickered and weighted) until dry.
Good luck.This is my personal signature.
Edited 7/7/2008 3:30 pm ET by MKenney
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