Does this happen sometimes or all the time?

[William Lessenberry]

Have some rough sawn 8/4 poplar, 11" wide x 64" long. I need to make a top for a cabinet that's 12" wide x 60". So I rip two pieces of this stock about 5 1/2" wide (have a 6" jointer) and then resaw it on the bandsaw to appx 1" thick. All 4 pieces bowed up 1/2"~3/4" in the middle of the board. I need to get these pieces to ~7/8" thick and straight enough to glue together for the top. Is that going to be possible or do I need to buy more lumber?
Is this an inherent problem when you try to economize by buying thick stock to resaw into thin boards or was this just two odd pieces of wood?
TIA,
BillL

[Mel Fulks]

Yes to “inherent problem”. It’s best to not buy material expecting to save money by re-sawing. But if you already have the material ….it is ,
sometimes …a good idea to re-saw,instead of “ re-buying”.

[glenn bradley]

In my experience it is sometimes. How the lumber is prepared, handled, and stored can contribute. Some properly prepared stock has internal stress that gets released.

[Alan Lightstone]

I'm in the sometimes group. I've had it work great, and a few times had significant bow. I tend to use plan for significant waste when doing it, so that if I need to remove more than I expect on the jointer/planer afterwards, I'm still OK to go. But it can get dicey... When it works great, it's a quick trip to the wide belt and done.

[Andrew More]

Yes to internal stresses being a problem. However, you also have to pay attention to the grain to see what the wood wants to do. Rift and quartersawn wood is less likely to cup on you because that's not the way the grain is running.

[Steve Eure]

If you have the time, you can sticker the wood on a flat surface with weight on top to help flatten it. This may take some time to do. Do not lay it straight on any surface without stickers under it. It has to be able to have air circulating all around it. I've done this with 8/4 lumber that did the same thing. It will work, but takes time. Avoid concrete floors unless it is high enough off the concrete that the moisture will not mitigate into the wood. It's a long shot, but it works.

[Lee Schierer]

There was likely a moisture difference between the exterior surface and the interior. When you resaw a board, you should stack and sticker the pieces with plenty of weight on the stack to hold the boards flat while the moisture levels equalize. A moisture meter will help with this process by telling you when the lumber has equalized. You may be able to save the lumber by doing this step now. Then as you joint or plane the lumber you want to remove equal amounts from each side and then stack and sticker the pieces for a while after planing. It sounds like a lot of work and it is, but it will be more work and cost to get new lumber.

[Mark e Kessler]

You need a moisture meter and buy a good one, how long was it in your shop to acclimate to the conditions? Don’t let it sit on concrete. It can happen period but I let it sit until the mc is the same as in the shop, skip dress it let it sit, rough mill, sticker let rest…of course i have the luxury of time and depends on what i am making if i need 80” bedposts i am more diligent than if with a cabinet door rail that is short

[Maurice Mcmurry]

It is a problem I have with plain sawn lumber. Not so much with quarter sawn. Un-balanced and incomplete drying can cause this too.

[Jim Becker]

Sometimes what you describe happens because of tension in the wood and quite often it's because of moisture imbalance between the original outside of the lumbar and the surface from the resaw that was in the middle previously. Sticker the material for a few days and see if it flattens out. You sometimes have to be patient relative to the moisture thing.

[Mitch schiffer]

This can happen when its dried too fast in a kiln and essentially case hardens to where the out side of the wood is dry but the core is not.

[Phillip Mitchell]

I just had this happen to me in the most extreme case I’d seen yet with some 8/4 walnut that seemed otherwise well behaved until I resawed it. In the photos you can see the extreme bow and how it actually split the wood fibers apart during the last 1-2” of the resaw cut. I thought my carbide blade broke for a split second before I realized what happened. That is about 5/8” bow out of flat (per side)

I’ve noticed this be much more of an issue with kiln dried woods from suppliers than with 100% air dried woods, though there are certainly other factors at play like internal stress from how the tree grew and how it was cut. I have resawn a fair bit of 100% air dried 10/4 walnut (in contrast with this 8/4 board I just got from a reputable supplier) that has literally not moved out of flat at all after jointing/resawing.

Wood is dynamic and often times not predictable.

[Kevin Jenness]

I just had this happen to me in the most extreme case I’d seen yet with some 8/4 walnut that seemed otherwise well behaved until I resawed it. In the photos you can see the extreme bow and how it actually split the wood fibers apart during the last 1-2” of the resaw cut. I thought my carbide blade broke for a split second before I realized what happened. That is about 5/8” bow out of flat (per side)

I’ve noticed this be much more of an issue with kiln dried woods from suppliers than with 100% air dried woods, though there are certainly other factors at play like internal stress from how the tree grew and how it was cut. I have resawn a fair bit of 100% air dried 10/4 walnut (in contrast with this 8/4 board I just got from a reputable supplier) that has literally not moved out of flat at all after jointing/resawing.

Wood is dynamic and often times not predictable.

I concur with all of the above, especially the last sentence.

That "crack" at the end of the cut will really get your attention!

[Richard Coers]

When you buy lumber with the intention of resawing it, rift or quarter sawn is the thing to buy. It is unusual for an issue with poplar, very common in white oak. The lumber dealer is the critical factor here. How it is dried in the kiln and what kind of stress relief they use is the issue. I've taken lumber back when it moves a ton during resaw. My dealer always replaces it.

[Steve Wurster]

I just had this happen to me in the most extreme case I’d seen yet with some 8/4 walnut that seemed otherwise well behaved until I resawed it. In the photos you can see the extreme bow and how it actually split the wood fibers apart during the last 1-2” of the resaw cut. I thought my carbide blade broke for a split second before I realized what happened. That is about 5/8” bow out of flat (per side)


I had a very similar experience recently with a 8' long piece of 8/4 white oak. It was completely fine until the very end of the resaw; and then, boom, huge bow in both pieces just like you had.

I left the pieces out to acclimate for a few days but they didn't fully return to flat. It ended up okay in the end though as I was able to cut one of them into shorter pieces and individually flatten those. Thankfully I had a few other 5/4 pieces sitting around that I used for the long pieces that I needed.

[Brian Tymchak]

Have some rough sawn 8/4 poplar, 11" wide x 64" long. I need to make a top for a cabinet that's 12" wide x 60". So I rip two pieces of this stock about 5 1/2" wide (have a 6" jointer) and then resaw it on the bandsaw to appx 1" thick. All 4 pieces bowed up 1/2"~3/4" in the middle of the board. I need to get these pieces to ~7/8" thick and straight enough to glue together for the top. Is that going to be possible or do I need to buy more lumber?
Is this an inherent problem when you try to economize by buying thick stock to resaw into thin boards or was this just two odd pieces of wood?
TIA,
BillL

That's a lot of movement.

If you didn't let the lumber acclimate to you shop for as few days, that could part of the problem. I acclimate lumber for a couple of weeks if I can. Also, you don't mention if you face jointed and planed before resawing. If not, that could also be contributing to the movement. Jointing/planing exposes fresh surfaces on the other side from the resawn face, which somewhat counters the overall movement by balancing the drying from side to side. If you didn't expose that fresh face, then jointing the rough face, then sticker/stack for a few days with weight might help.

[William Lessenberry]

The board was in the shop over a week. I jointed one edge so that edge would ride smooth on the bandsaw table when I cut it, but I didn't joint or plane any other surfaces before cutting. I'll sticker and weight these boards for other projects, but I'll need to go to the blue store and buy a couple of 1 x 8's ($$$) so I can get this job finished.
Thanks for the help, always living and learning.
Here's a pic
BillL

[Andrew Seemann]

Generally, the more closely-sized the rough board is to the finished size, the better. The more rips, resaws, passes on the planer or jointer, the more chance of warping there is from internal stress, moisture differential, and general cantankerousness in the wood.

It's pretty rare for me to resaw boards that don't warp afterwards. I've had boards that have been in the shop for a decade warp after cutting, so acclimatizing only gets you so far. Even if you do everything "right" sometimes it still doesn't work. That said, if you want 7/8 stock, you are almost always better off starting with 4/4 or 5/4. Trying to use 8/4 will almost always warp, at least in my experience in my climate.



That said, for your table, I would probably plane the boards to 7/8, alternate the warp up and down, and use biscuits to hold them together/in line for the glue up. 1/2"-3/4" warp on boards for a table top isn't horrible, and the glue up will probably cancel out the warp just fine as long as you can flatten them relatively easy when you put them together. If you can joint and plane them down to having only 1/2" warp, that would be even better.

[Mike Wilkins]

Sticker them for a few days/weeks with some weight on top and see if they equalize and flatten. Resawing will open up the moisture inside the lumber after it is open. Might work.

[Anuj Prateek]

I resawed 8/4 soft maple sometime back. It started cupping and bowing within minutes. Like an idiot I flattened and laminated them right after. Overall glued panel cupped badly. At this point boards were ~3/4" thick.

It was sitting in shop for last 2-3 weeks. Day before yesterday I ripped the panels. Flattened them back again, and ended with 5/8" thick boards. Yesterday I found them slightly cupped and bowed again. This was disappointing, most of CAD 100 has turned into saw dust.

I guess it's the tension in wood that others have pointed towards. I have 10' of 8/4 maple left. Not going to resaw them.