Resaw waste

[lou Brava]

I'm fairly new to resawing thin veneer and wondering if I'm doing it wrong or is it to be expected & how to remedy what I see as a problem & at $11.00 a BF will get expensive. Problem is the board I'm resawing ends up super bowed & cupped after it's down to about 1" to 7/8" thick. I'm resawing 8/4 x 7 1/2" x 26" Walnut the MC is about 6-7% 1 face & 1 edge joined perfectly flat & sq.
I'm reaswing at 3/32" thick for a bent lamination. I noticed after sevaral cuts there was gap at back of fence, made a few more cuts gap getting worse. I stop & see that the board now about 3/4" thick is bowed so I start again with pressure very close to the blade and just let the back of board float & can still get a decent cut until the board cupped and than it's game over. Board is now aprx. 1/2 thick & good for nothing. I'm thinking maybe 8/4 stock was bad choice should have used 5/4 ? Or flip board & alternate cut face every time ? Or live with it and expect this to happen. I've done some White Oak 8/4" & 5/4 Cherry & didn't have this happening.
Thanks
bow.jpg

[al ladd]

In my experience it's hit or miss with this sort of thing. Starting with thinner stock makes it less likely to be a problem. Every cut releases tension--sometimes a lot. You might simply put the board under weight and wait a few days (but waiting is often not an option for people). Cutting off alternate faces, to reduce the chance of a moisture gradient developing, will possibly help. Sometimes a cup or bow will resolve in just a few hours as the newly exposed face(s) reaches equilibrium. With a powerfeeder or other powerful "flattener" or with a "point fence" you might get away with additional cuts as is, convex side to fence. Your veneers don't need to be flat, and a planer or drum sander will make them uniform thickness.

[Cliff Polubinsky]

One possible cause is that the surface and the inside of the board are not the same moisture level. So if you keep slicing off the same side the difference between moisture levels of the outsides of the board drift farther apart with each slice causing the board to bow.

It might help to alternate the side being sliced so the moisture level of the two sides will be closer. Worth a try in any case.

Cliff

[Mike Cutler]

Yes, it happens. Sometimes even after you pick the perfect q-sawn board, and do everything right, it still does. Tropical hardwoods do it also. The wood is going to do what it does.
If you're going to keep doing this type of work, it may be time to consider a bandsaw. It's much more forgiving than a table saw, and the waste is considerably diminished.

[Andrew Hughes]

If your resawing with your tablesaw im impressed you got that far.
A tablesaw blade creates a lot of heat inside wood.

[Jamie Buxton]

I start by gluing the veneer stock to a backer board. The backer board goes on the face which is away from the fence. The backer has no effect on the first slice, but as I take more slices, it keeps the stock flat and straight.

Also I use a tall fence that goes only a couple of inches past the bandsaw blade. If the veneer curls up as it comes off the blade, the short fence doesn’t let the veneer try to push the stock away from the fence.

[Lee Schierer]

I recently resawed a scrap piece of treated lumber that was 3/4" x 5-1/2 x 30. As soon as I finished the cuts, I put the outside faces against one another and clamped them tight along the length. I left them clamped for a week or two. Then I ran them through my planer to clean up the sides that had saw marks. Again I clamped them flat against each other. The pieces are now 1/4" thick and completely flat even with out the clamps. They were damp to the touch when they were cut apart. The hay been un-clamped for several weeks now and are still flat.

[lou Brava]

No chance I'm using a TS the stock is 7 1/2" tall ! I also use the fence Derek Cohen came up with (forum poster) that's in the latest issue of Fine woodworking mag. I think it is a moister thing as I'm getting higher readings in center of board.
James that gluing to a backer board sounds like a good way to go, it seems it would be near impossible for the board to bow or cup.
Thanks everyone

[John TenEyck]

6 to 7% MC sounds good, but not if the board has a large gradient or the EMC of your shop is somewhere else. Wood goes wonky when you cut it because of a moisture imbalance or because it has internal stresses. IME, it's more often due to a moisture imbalance. There's no substitute for the stock to be at EMC with your shop. Having said that, you usually can slice veneer from a board that's not at EMC as long as the MC of that board is pretty constant AND you bring it into your shop and slice it immediately, before it has time to develop a gradient. A tablesaw is a poor choice for slicing veneer, and even worse if trying to do it on a board that's not at EMC with your shop. But if that's what you have, then that's what you use. In that case, I would prep the board so that it's 4 square, and then alternate taking slices of each face to try to keep the gradient as uniform as possible. I would do all this as quickly as safely possible.

John

[Richard Coers]

What does the wood moisture really scale at, if you say it's ABOUT 6-7. What moisture meter do you use and do you just measure the outside of the 8/4 or do you measure when you get to the inside. Is it kiln dried? Walnut is easy to dry, so it would really be a bad kiln operator to screw it up. One thing about table saw resawing is that there is more heat involved in the cut and if the walnut isn't stress relieved in the kiln, you get your issues.

[Jim Morgan]

No chance I'm using a TS the stock is 7 1/2" tall ! I also use the fence Derek Cohen came up with (forum poster) that's in the latest issue of Fine woodworking mag. I think it is a moister thing as I'm getting higher readings in center of board.
James that gluing to a backer board sounds like a good way to go, it seems it would be near impossible for the board to bow or cup.
Thanks everyone

Folks were misled by the photo in your original post.