Resawing frustration.. Anybody?

[Rick Fisher]

This is my frustration..

I buy premium wood.. No borg punky crap.. I buy 100 bf lots of 8/4.. Fir, Maple, Oak, Sapeli, whatever..

This example is QS Red oak, 8/4, Kiln dried from a reputable hardwood wholesaler. I have to say, it doesnt matter what species..

This is one of todays peices..

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1150169.jpg

I cut it to roughly the appropriate length.. Then face joint and edge joint. This one is 49" long.. for a matched table top..

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1150171.jpg

Then I resaw..

Every time, the wood warps inwards.. EVERYTIME...

Usually its 2x6 thru 2x10..

So I ask myself.. What was the point in Jointing that ???

This example is not too bad. most of them, if I make them perfectly flat, they will be 1/2" thick..

I have been to the new suppliers warehouse, its heated, inside.. I changed suppliers because of this.. its always been this way..

It occured to me tonight.. am I doing something wrong?

This wood sat in my shop for 10 days.. I face jointed it 48 hours ago and let it sit... Everything is fine until I resaw..

I know .. I know .. releasing the tension in the wood.. but gimme a break .. Everytime its the same tension.. same inward bow..

[Rick Fisher]

I should add.. I have measured the stock between the fence and blade.. its consistent thickness.. I use featherboards..

Usually, I make these table tops as flat as possible, while maintaining thickness, glue up all the warps the same way and use pocket screws to make it flat to the aprons..

Is this just the way it is?

I use 8/4 stock because I like to match the grain up.. it makes table tops more attractive IMO.. In this case, the whole table top is from the same board.. So the color and grain are consistent .. If there is any figure, I book match the nicest figure in the center of the table. For that reason, I dont buy flat 4/4 stock .. I buy flat 8/4 stock and make my own warped 4/4 stock.. :)

(Gotta admit.. venting like this makes ya feel better.. maybe the women are onto something ??? nah.. )

[Simon Dupay]

8/4 stock is going to have more stress in it then 4/4 stock and with all that heat from resawing it's going to warp no matter what. It's better just to use 4/4.

[Joshua Layne]

Using 4/4 - maybe starting with 10/4 and resawing for where you really want the book-matched pieces (the extra thickness adds cost, but also adds some stability (I would think) and gives a bit more leeway in jointing the boards and getting a thick 4S board at the end) and using 4/4 other places where it doesn't matter (lower cost here, in my experience - 8/4 commands a premium)

[Bruce Page]

Rick, what kind of saw? What blade? What tension? What HP?
These all have a bearing on resawing. The only time I have had bowing problems is when I used a dull blade.

Here’s a resawing thread I did when I was making the back panels for a cabinet. I cut them down to 5/8” and finished them at ½”.
http://www.sawmillcreek.org/showthread.php?t=61089

[Rick Fisher]

Rick, what kind of saw? What blade? What tension? What HP?
These all have a bearing on resawing. The only time I have had bowing problems is when I used a dull blade.

Here’s a resawing thread I did when I was making the back panels for a cabinet. I cut them down to 5/8” and finished them at ½”.
http://www.sawmillcreek.org/showthread.php?t=61089

The blade is a nearly new 1" Lennox Trimaster, 3 Tpi.. The saw is a 24" SCMI with a 5hp motor.. It will resaw 2x6 Oak as fast as you feel like pushing.. under 45 seconds for a 4' length..

I agree that the 4/4 stock is straight.. but somebody made it into 4/4 stock !!! lol. Why did it not warp when it was cut origionally..

I wonder if its the humidity in my area? I live on Vancouver Island.. Rain capital of North America.. This oak was likely cut and dried in Kentuky or some other place?

I have been reading much of the night.. if the surface of the oak picked up a bunch of humidity.. but he center stayed bone dry.. the outside would swell, but not warp because it would be swelling all the way around??

when the board is ripped, the swollen outside would finally be able to move and the dry side would not ...

This could be rubbish.. but it happens with every species..

[Faust M. Ruggiero]

Rick,
Sorry for your frustration but what is happening to you is not a result of bad wood purchases, poor blade choice, improper technique or anything else within your control. It is all about the nature of wood. There are always going to be stresses within wood that cause movement when you release them. Re-sawing thick lumber releases stress. Some of that stress is pronounced by the process of drying. Our job as woodworkers is to understand the wood and know how to deal with wood movement. An 8' table top is almost impossible to joint dead flat and hold flat, especially at a finished thickness of 3/4".
You have to choose your boards carefully to even have a chance. Your first misstep was deciding to re-saw from thick stock. I am sure your intention was to book match but I can't think of a wood specie I would trust to remain flat when being re-sawn from thick stock. You should have bought 5/4 stock with the intentions of finishing somewhat thinner. The thicker you make the top, the better chance you have of keeping the planks straight and true. You should have hand chosen the boards by sorting through the suppliers stock. Find boards that are already somewhat flat. Believe it or not, stresses will be relieved when you joint the first face. That's why it is a good idea to remove as much stock from each face when surfacing the boards.
Your choice of wood is important. Oak, though fairly stable, has a lot of stresses due to the rings of early as versus late season growth. Where the board came from in the tree has a lot to due with how flat it wants to remain. Especially, look at the direction of the growth rings. Quarter sawn wood is less apt to move than plain sawn.
I know you want to make a solid wood top but if book matching the boards is your major goal, you will have the best luck resawing into 1/8" veneer and laminating to a substrate like MDF. Of course, that process opens up another can of worms.
You can't fight the wood. You have to learn it's behavior and work with the movement.
fmr

[Ben Abate]

Rick,

Funny you post this, I have been using quite a bit of poplar for a substructure lately. I have been resawing quite a bit also with mixed results. It seems that your end result would frustrate me also. I have been getting some warping but mine has been more of a cupping than a warping end to end. Now, this is what I noticed with the poplar. I have resawn 6/4 into 5/8 thickness and it warps, then I had to resaw some pieces into 7/8 inches and they were flat. I have been gluing up large blanks to be turned into 3 ft columns. 6x6x36. after flattening I ended up needing a bit more for when I did the final squaring so I added these pieces.

As I said earlier, mine was cupping and not warping like yours. Don't know what to tell you. I have with good results resawn very wide Spalted Maple and Quarter Sawn White Oak into very thin slices. I use the same blade as you do and I have a 24 inch Laguna with 7.5 hp. I don't think speed has any bearing on the warping results. As you and everyone else has said, tension in the wood has to be it. But you would think, if the wood was dryed properly it would not hold that tension. Don't you????

Sorry I have no solution for you but I hope someone here will confirm what we are talking about.

take care
Ben

[John Keeton]

Rick, have you tried resawing the stock, then stickering it up to "rest" for awhile before you further machine it? I have found that pieces that warp like you say - and many do - will often straighten back out over a couple of weeks.

[Ken Higginbotham]

Hum... I am by no means a woodworking expert but it seems as though the outside edges have more moisture content than the inside which would make it bow in as in the pictures. The only thing I can think of to solve this would be to try cutting it as soon as you get it or let it sit in the shop for longer periods of time. Hope that made sense... If somebody already pointed this out I apologize :)

[Mark Philippi]

I am no expert but I have an idea of what mey be happening. When you get your 8/4 boards the moisture level in the center is higher than it is on the faces. When you resaw it the wood which was the core is now a face only these "new" faces are wetter than the original fasces. As they begin to dry the face shrinks pulling in the curve you are experiencing.
I don't have a ready solution for this maybe longer acclimatization or begining with thicker stock, so that both faces are "new" and the original faces are scrap mmay help.

[Phil Thien]

If the wood bows immediately after resawing, then that is the result of internal stresses in the wood being released. My experience has been that maple is more reactive in this regard than other species, but they all do it to a degree.

If the wood bows several hours to days after resawing, then that is the result of moisture imbalance (still wet on the inside). You can try to find a supplier that does a better job w/ the kiln. I've also found air-dried lumber (stuff that has been air-dried for 2-3 years) resaws better than much kiln-dried stuff I've worked.

[Keith Harrell]

I have the same problem with walnut and trying to use some 8/4 lumber for 4/4. The boards were 8" wide and it really popped apart as I cut the last 1/4" of the board. As pointed the internal stress is hard to read.
These boards had been in my shop for 3 months before I cut them.
Not much help other than it not you that's creating the problem.

[Mike Wilkins]

I don't think it is your technique nor the timber. I have seen the same thing happen when I resaw something of that thickness here in NC. A thicker stick will release tension due to different moisture levels on the interior. Someone has already suggested letting the wood sticker for a few days after resawing.
Let me offer another suggestion: since you like to book-match the table tops,
why not resaw the material into veneers in the 1/8" range and laminate some stable substrate?? May be worth a look. More work but less chance of the bowing/cupping you are currently experiencing.

[glenn bradley]

Your report that the cut line is reasonably straight and that the resulting thicknesses are consistent says you are doing everything right on the cut. I try to cross cut my pieces to rough length to minimize the bow and therefor minimize my loss at the jointer and planer.

For instance, your pic shows you may have an 1/8" between the table and your board if you set it on your bench allowing it to arch up like a bridge. If you cut that length in half you may only have 1/16" of rise which might be acceptable to joint out.

Just to help set your expectations, I generally expect to lose 1/8" of thickness (more in pesky material) to final milling of rough lumber. That is; I expect to get two good 1/2" thick boards out of a piece of 5/4 material. Sometimes I do much better, sometimes not.

[James White]

The reason there are so many opinions on what is happening is because it can be caused by many factors. The worst being it was dried improperly and has case hardening. This is when the outside of the board dries with the cells of the wood stretched because the center of the board did not dry with it. That will cause exactly what you have. The next is you are getting the boards dried from 6-8% MC and bringing it into your shop that has an equilibrium greater than that. Say around 10%. So the outside of the board is acclimated and swelled but the inside is dryer and still in a shrunken state. This will be relieved as John suggested by letting it rest for a few days after resawing. Or you can put a dehumidifier in your shop along with a inexpensive Hygrometer and control your shop humidity so that this doesn't happen in the first place. Tension in the tree from growing on a slope usually will not show up symmetrical the way it did for you on this board. Heat generated by the saw blade could also do this. So what you need to do is play detective and eliminate as many of these variables as possible. I am betting on the BC humidity as the culprit or poorly dried wood (case hardened).

James

[Lorne Steed]

Hey Rick; I live just down the road from you in Nanaimo and i have had the same problem. It is because a lot of the wood is just absorbing moisture from its kiln dried state to the ambient moisture level which is around 11 to 13% around here. As John said, try just letting it rest and have the cut pieces settle to the moisture content of your shop for a few days, and then proceed to your machining. It seems to mitigate the loss somewhat. You could also lightly mist the culprit side before resting the wood- it might help to relax a bit by evening out moisture content.

[guy knight]

allot of your problem can be attributed to difference in mostisure content from the outside to the inside as others have said try stickering it and on wider boards sticker and clamp the ends with some cauls and leave it so equalize for a few days and when surfacing try to take some of each side to keep the moisture the same on both sides

[Mike Cruz]

Everybody is WRONG. The solution is to buy your stock from a BORG and it will already be exactly 3/4" and warped without all the hasstle of resawing. Man, you guys make this stuff difficult!

[Jeff Willard]

:confused: Don't the pre-warped stuff cost more tho'?

[Wayne Hendrix]

:confused: Don't the pre-warped stuff cost more tho'?

Around here yes, even more if the forklift driver dinged the ends of the boards when unloading them.

[Alan Schwabacher]

If the concave side of the curve is always inside, it looks like your wood storage space is more humid than your supplier's. The outside part of the wood wants to expand compared to the inside, and was in balance before cutting. Moisture would expand the wood, and if you let it stand in your shop, it will take up or give off water until it matches the humidity of the shop. It would take quite a while for thick stock to become the same water content throughout, and that might never happen if the shop humidity changes with season, providing a moving target. That's why the easy solution to keeping stock pretty stable is to take the same amount off each face.

A dehumidifier might help, or stacking and stickering the resawn stock to see if it stabilizes after moisture equilibration.

[James G. McQueen]

Unfortunately wood is not the perfect medium. We want to manipulate it to do what we want but sometimes the wood has the last word. We take a product of nature and expect it to cooperate. As far as I can tell it was never intended to be made into furniture but we make it happen.

Your frustration is not uncommon. Trust me I have been there. If it wasn't for my stubborn disposition I would have given up this game a long time ago. My profession is in the wood business and I have spent the last 15 years learning all I could about wood and woodworking.

The stresses in the wood could be from drying or from the tree itself. Regardless of the reasons for this. You need to find a way around this.

If You are keen on bookmatching see if You can find someone who will sell You a whole log that has been flinch sawed to the thickness you desire. Flinch sawing is when the log is cut in pieces starting from the top and working to the bottom. The pieces are reassembled and dried exactly as they were in the log. It forms a perfect bookmatch and this may give You better colour match.

If You are dealing with these boards that are bowed You can also try a trick I discovered a long time ago. It seems to work most of the time but not always. Feed the boards through Your planer with the bow or hump up(your resawed surface down)Take a few passes then look down the length and see if the board is straighter. (A great deal of the time it will help to relieve the tension) If it straightens then leave enough thickness to do the bottom side. I've seen red oak many times bow the other if you take off to much. Check it every pass and remember to keep the bow up.

Good Luck

[ian maybury]

Another 'non expert' here but some thoughts.

If as seems likely the problem is variable moisture content through the as purchased kiln dried timber then that's the issue that needs investigation.

It may very well be the case that machining after resawing will bring the board straight, but if it's got an uneven moisture distribution then it probably going to warp again anyway as it equilibriates.

It would be interesting to test one of your freshly resawn boards immediately with a moisture meter to see if the moisture content of the freshly resawed face is much different (and in which direction) to that of the one that has been outside for quite some time. (if the fresh face is wetter, then the problem is likely that the core did not dry well in the kiln, if the fresh face is dryer then it's probably picking up moisture in your shop)

Measuring again at intervals as it assumes the curve would maybe say whether it's drying or mositure gain that is subsequently taking place.

Either way it seems to me that for this reason that there's not much point machining it until it has equilibriated.

What i can't hazard a guess at is whether resawing, then sticking it straight until it equilibriates, and then machining it will do the trick - this would need to be the natural 'straight' condition of the wood, or else it would need to 'take a set' (straight) during sticking.

I'm guessing that if the moisture distribution was not even when the freshly rough sawn and as a a result straight appearing timber went into the kiln that it would have warped badly as it dried and the moisture distribution changed - which would suggest that if the rough sawn kiln dried timber is pretty straight when received that any moisture imbalance is symmetrical and likely due to faster drying in the kiln at the outer surface than at the core.

I recently had a look at sourcing well equilibriated oak in about a 4 in thickness for a possible project, and was told by more than one source that it wasn't feasible - except perhaps by extended air drying followed by kiln drying - and that commercial kilns (that usally seek to accelerate the drying process to the max) were unlikely to get into that sort of work on cost grounds. It was also said that it would be tough to avoid cracking/checking during such a process....

[Rick Fisher]

I am in the building supply business. On this part of Vancouver Island, we have a lot of woodworkers.. So while on the floor today, I asked a few..

This is the response I got.. :)

"That wood was dried to 6% - 8% ..
We live in a rain forest.. the humidity here is 12%...
The outside has swollen and the center has not.. "

He also said

"If you sticker it after it cut and let the dry side swell as it reaches 12%.. the wood will go sorta straight..
He also said if I dont sticker it .. it could twist as different parts of the board will absorb humidity faster than others.. "

This guy lives on one of the gulf islands and is what we call .. a hippie woodworker.. lol.. Most smoke a lot of pot, own grow-op's and do a lot of woodworking.. lol..

I think all you fellas who suggested this where right.. I think this guy knows what he is talking about..

Thanks for all the replies..

As suggested by others.. the cupping is always as depicted in that picture.. always cupping toward the dry side.. Everytime..

So it makes total sense.. For some reason, understanding it makes it less frustrating.. When I dont really know why, I tend to blame myself..

[Ken Higginbotham]

So here is a followup question for the group; Do some woods warp more than others? I would think not but the only thing I have worked with to any extent is pine.

[Sean Nagle]

This guy lives on one of the gulf islands and is what we call .. a hippie woodworker.. lol.. Most smoke a lot of pot, own grow-op's and do a lot of woodworking.. lol..

I want to be a "hippie woodworker" :)

[Chris Friesen]

So here is a followup question for the group; Do some woods warp more than others? I would think not but the only thing I have worked with to any extent is pine.

Absolutely. As humidity changes, wood will expand or contract differently tangential to the growth rings that it does radially outward from the core of the tree. The difference between the tangential and radial dimension changes is what causes warping.

The link below has radial and tangential shrinkage values for a bunch of wood species. The larger the numbers the larger the dimension change, and the closer the two numbers are to each other, the less likely the wood is to warp. For extreme examples, compare Overcup Oak (5.3/12.7) to Honey Locust (4.2/6.6).

http://www.woodcentral.com/bparticles/woodmove.shtml

In addition, quartersawn lumber will generally warp less than plain-sawn lumber because the radial shrinkage is less than the tangential shrinkage. By quartersawing it, the radial direction is oriented across the larger dimension of the board, reducing overall dimension changes.

[Rick Fisher]

So here is a followup question for the group; Do some woods warp more than others? I would think not but the only thing I have worked with to any extent is pine.

In the last year, I have mainly worked with Fir, Maple, Oak and Sapelli..
The Maple and Sapelli are IMO much worse than Fir and Oak..

Having said that, the Fir and Oak have both been only quartersawn..

Fir is actually not bad at all.. My gut feeling on the fir is that since its from the Island I live on, its more comfortable with the humidity..

No idea if that's true.. lol.

[Ken Higginbotham]

Thanks for the info Chris.

I like working with 2x pine from HD because it's easy to get. I cut it down to whatever size I need & joint & plan it square. But I've learned not to stock pile too much because it warps pretty bad after seral days in the shop.