Crappy Stock?

[protectedvoid]

So, I had two boards of 8/4 hard maple, each 12" wide by 66" long that I purchased a few months back. I had them pre-milled, S4S, to 6/4 x 11.5"W x 50" L. That was my first mistake. I got them home, and they moved...badly. Cupped, bowed, AND twisted. I also had some checking on one end of one of the boards. This weekend, I decided to rip each board in half (lengthwise), mill them flat & square, then re-glue to create a flat surface. While I was successful, I lost another 2/4 thickness. I was able to get them glued up, and they "appear" to be stable at this point.

So, I paid for 8/4 stock and ended up having to drastically reduce it to get it flat and stable. Final dimensions: 4/4 x 9.25"W x 45"L -- Now, a couple caveats...this was the first 8/4 lumber I had ever purchased, and was my first purchase from my hardwood dealer. I now know the stock my dealer supplies is supposed to be kiln dried to 7% - 12%. I have purchased other stock from them that has been very stable...but for some reason, I seem to get quite a bit of movement in the hard maple & curly maple I've purchased.

What I'd like to know is, is this a common experience with 8/4 stock? Is this a more common experience with Maple vs. other Hardwoods? Is there anything I can do to mitigate this type of loss or drastic movement in the lumber?

*** Edited to fix the final dimensions from 2/4 to 4/4 ***

[iSawitFirst]

You never know how much tension is in a piece of wood until you open up the faces or rip it. Whenever I rip 8/4 boards I cross my fingers that I'll get two 3/4 boards out of it especially if its not quarter sawn, straight grain. That gives only a quarter inch of material on each board to make corrections.

There may have been a moisture content issue as well. Initially taking only 1/8" off of each face would have caused any inherent movement that hopefully could have been corrected with the second 1/8". I'm guessing though that most of the movement was caused by internal stresses.

Did you lay the milled piece flat on the floor or did you sticker it? I once made a serving tray out of 1/2" Mahogany. I took care to mill it to thickness in layers to prevent warping and ended up with a perfectly flat 16" x 12" piece. Unfortunately, after my final planing I laid the piece on my table saw and left it there overnight. The next morning it had cupped about 1/6 ", just enough to wobble on a flat surface.

Wood is tricky.

[protectedvoid]

Did you lay the milled piece flat on the floor or did you sticker it?

Actually, those pieces were stored on end angled against a wall, so that both faces could "breathe", and that's how they've been stored after each successive cut. Actually, that's pretty much how I store all the lumber I get since I don't have the storage space to sticker / lay them flat.

It is rather disappointing to lose that much lumber, though. But, live and learn.

[Guest Trace]

I would guess that it is not the maple. We make propellers from hard maple, some of which lays in the racks for years. The process starts with a rough 5/4 milled to about .9", and 8"-10" wide. Then glued and clamped to dry. The production is a start to finish in one continous operation, taking about three days. We do have some waste, but very little from checking, warpage or cupping.

[protectedvoid]

I would guess that it is not the maple. We make propellers from hard maple, some of which lays in the racks for years. The process starts with a rough 5/4 milled to about .9", and 8"-10" wide. Then glued and clamped to dry. The production is a start to finish in one continous operation, taking about three days. We do have some waste, but very little from checking, warpage or cupping.

So then, I'm thinking what I should take away from this is that I shouldn't mill anything until I'm ready to do whatever lamination / assembly is going to be required from start to finish. Which makes sense. On the other hand, this particular batch of maple moved within hours after being cut / planed and sanded flat...as in it was straight when I picked it up at 4:30pm, and when I went to cut it to final length at 9:30pm that same day, one board had already cupped & bowed (slightly), while the other had severely twisted, with some bowing as well. From that point forward, that was that.

I can, at least, confirm that now that it's at 4/4 and a two stage glue up, it has remained stable and flat.

[Bob Rozaieski]

My guess is internal stress in the board, not a moisture issue. A board that has little to no internal stress that is kiln dried properly should stay relatively flat, regardless of length/width/thickness. However, if there is significant internal stress, or if the board was dried too quickly causing case hardening, it will move almost immediately (or within a couple hours) upon cutting/planing. Sometimes there's just no way of knowing if the board has internal stress until you start working it. In my experience, boards like this just don't stay flat, no matter how much you plane off or how many times you re-flatten. If there's a lot of built up stress, removing more material only serves to release more stress and make the board less stiff, therefore, less able to resist the stress. If you have to use these boards, it's best to cut, plane and assemble all in the same session. If you can't do a full assembly, make parts and assemble the parts dry until you can finish other parts and assemble the entire thing. The dry assembly will help to keep things from getting too out of whack. Still, sometimes you just get unlucky with a board and it's best to just bite the bullet, buy a new board and use the "bad" one for other things.

[protectedvoid]

My guess is internal stress in the board, not a moisture issue. A board that has little to no internal stress that is kiln dried properly should stay relatively flat, regardless of length/width/thickness. However, if there is significant internal stress, or if the board was dried too quickly causing case hardening, it will move almost immediately (or within a couple hours) upon cutting/planing. Sometimes there's just no way of knowing if the board has internal stress until you start working it. In my experience, boards like this just don't stay flat, no matter how much you plane off or how many times you re-flatten. If there's a lot of built up stress, removing more material only serves to release more stress and make the board less stiff, therefore, less able to resist the stress. If you have to use these boards, it's best to cut, plane and assemble all in the same session. If you can't do a full assembly, make parts and assemble the parts dry until you can finish other parts and assemble the entire thing. The dry assembly will help to keep things from getting too out of whack. Still, sometimes you just get unlucky with a board and it's best to just bite the bullet, buy a new board and use the "bad" one for other things.

Ok. Thanks for the additional explanation. That makes sense. As of now (9:04pm), these boards are still flat, so I'm going to assume the glue-ups I did are what's helping to keep them that way. So, I picked up about 9bf of 5/4 big leaf maple yesterday. I'm going to face laminate those to these "flattened" boards, making the big leaf the actual workbench surface, and these "troublesome" boards the substrate. They're also going to be reinforced with 3 pieces of 5/4 x 2" Jotoba dadoed into them on the bottom (width wise) to give some additional strength and prevent flex.

See any problems gluing two larger 5/4 boards to these to get my 2" thick top given that the big leaf maple hasn't moved at all since I brought it home?

[Bob Rozaieski]

The glue up will probably go fine, but try to pay attention to the end grain when you glue the boards together. Laminating boards face to face introduces a lot of moisture to one wide face of each board, which can cause both boards to cup due to the unequal moisture gradient through the boards. If the boards cup before the glue dries, they'll stay that way and you'll have to plane a lot of material off both sides to get them flat again. Try to glue them together so that the bark side of each board is the joinery surface. So if you stand the assembly up on edge, the rings on the end grain should look like this ))((. Arranged in this way, the boards will tend to cup toward each other rather than away from each other (which will pull the edges of the lamination apart) or in the same direction (which will cause the entire lamination to take on a permanent cup that will have to be planed out of both sides). Gluing with the bark sides touching should help to resist the cupping until the glue dries and hopefully result in a flatter lamination. Use plenty of clamps and cauls across the lamination so that the center of the lamination doesn't bulge out while the glue is drying. Also, if you can, try to do the glue up and let it dry on a flat surface to prevent the lamination from taking a bow as it dries.

Laminating can be fussy because of the moisture imbalances introduced, but if you arrange the boards like I mentioned and do everything on the flattest surface you can, you should be able to minimize any major distortion. You will likely still need to reflatten the lamination some after the glue dries and the lamination's moisture level re-equilibrates (I'd say give it a week after glue-up), but if you arrange the boards as above, and do things on a relatively flat surface, the additional amount of flattening required should be minimal.

[protectedvoid]

The glue up will probably go fine, but try to pay attention to the end grain when you glue the boards together. Laminating boards face to face introduces a lot of moisture to one wide face of each board, which can cause both boards to cup due to the unequal moisture gradient through the boards. If the boards cup before the glue dries, they'll stay that way and you'll have to plane a lot of material off both sides to get them flat again. Try to glue them together so that the bark side of each board is the joinery surface. So if you stand the assembly up on edge, the rings on the end grain should look like this ))((. Arranged in this way, the boards will tend to cup toward each other rather than away from each other (which will pull the edges of the lamination apart) or in the same direction (which will cause the entire lamination to take on a permanent cup that will have to be planed out of both sides). Gluing with the bark sides touching should help to resist the cupping until the glue dries and hopefully result in a flatter lamination. Use plenty of clamps and cauls across the lamination so that the center of the lamination doesn't bulge out while the glue is drying. Also, if you can, try to do the glue up and let it dry on a flat surface to prevent the lamination from taking a bow as it dries.

Laminating can be fussy because of the moisture imbalances introduced, but if you arrange the boards like I mentioned and do everything on the flattest surface you can, you should be able to minimize any major distortion. You will likely still need to reflatten the lamination some after the glue dries and the lamination's moisture level re-equilibrates (I'd say give it a week after glue-up), but if you arrange the boards as above, and do things on a relatively flat surface, the additional amount of flattening required should be minimal.

I have a large piece of granite (2' x 4') that will give me plenty of flat surface to do the lamination on. And I had definitely planned on using plenty of clamps & cauls to make sure the boards stayed flat across their width until the glue dried. So, here's another question. I'm not sure I'll have enough cauls, though. I also cannot spare any extra scratch at the moment to purchase anything like bow clamps, etc. Do you have a solution for making 30" cauls out of random hardwood, and what the dimensions might need to be?

[Bob Rozaieski]

I have a large piece of granite (2' x 4') that will give me plenty of flat surface to do the lamination on. And I had definitely planned on using plenty of clamps & cauls to make sure the boards stayed flat across their width until the glue dried. So, here's another question. I'm not sure I'll have enough cauls, though. I also cannot spare any extra scratch at the moment to purchase anything like bow clamps, etc. Do you have a solution for making 30" cauls out of random hardwood, and what the dimensions might need to be?

No specific dimensions needed. Just take whatever you have available, scrap hardwood, 2x4s, whatever, plane them to a slight convexity so they clamp a little tighter in the middle, and have at it. Just a few swipes with the plane should suffice. The curve does not need to be dramatic, just slight, almost not noticable.

[protectedvoid]

No specific dimensions needed. Just take whatever you have available, scrap hardwood, 2x4s, whatever, plane them to a slight convexity so they clamp a little tighter in the middle, and have at it. Just a few swipes with the plane should suffice. The curve does not need to be dramatic, just slight, almost not noticable.

That works for me.