Keeping it flat

[tlempicke]

I just did a 3d carving of a piece 9 inches by 11 inches. Started with 1 inch lumber (Red Oak)

The piece is a top for a jewelery box for my Granddaughter.

When finished it is beautiful but has a "Cup" to the underside.

I can figure out how to clamp it to remove the cup, How to I KEEP it flat?

[phil_o]

Was the wood flat before machining?
If the oak was flat before machining was the grain fairly straight or highly figured? Oak that is highly figured is more subject to movement. That is why straight grain is preferred for door frames and figured grain is used for door panels.

Phil

[Ken Sully]

TJ had an on line training on flattening wood. Take a look in the on line videos.
Might give you an idea

[cowboy1296]

When you figure it out let me know.
First I start with wood that is dry. Then it is cut into strips and glued back together mix matching the grains. Then it is sanded smooth. Every 3-d carving that I do warps a little. But mine are wall hangings and do not show, as a lid I am sure it can be frustrating.

[tlempicke]

Where might I find that on line training video? Could you please post a link or just a cut and paste of the url?

[cowboy1296]

The video was about taking a wood stock and making it flat. It did not address the issues of warping boards after the cut. But I did learn some stuff watching it.

[srwtlc]

If you have room (thickness) enough, you can try hollowing out the back side some to relieve or balance the tension. If that doesn't work and you have some wiggle room, after hollowing the back side, you could lap it flat on a flat surface with some sheet sandpaper adhered to the flat surface.

[supertigre]

Start with quartersawn wood and carve into the edge grain. The part "may" be straightened by machining the other side of the wood. The board you started with had some stresses in it, when you machined it you removed some of the material that was balancing the stress and the part moved to re-balance the stress, machining the other side of the material may relieve the stress on that side allowing the part to straighten.

[Ken Sully]

Here you Go. Hope it helps!



http://www.shopbottools.com/Training/Videos/WarpedBoards.wmv

[chiloquinruss]

"try hollowing out the back side some" Works for me! :D Russ

[myxpykalix]

Tom
I had this same issue on a glued up lid for a toybox of dried walnut and the problem is by removing so much wood from the carving you relieve some of the stresses of the wood (the part that keeps it straight) that the curling occurs.

I had to start over and the only way i cured it was to have more on the bottom that is uncut and can hold the pressure of the cut part.
So if you are using say a 1/2 piece of wood, try again with a 3/4 piece or add at least 1/4 to the original size to start with.

I tried even gluing pieces crossgrained together to give me the thickness i needed, that helped some.
Here is something else i did as an experiment. I took and routed a small groove across several boards and "implanted" a small rod. I would say that it was a success but you have to be very careful about placement within and depth of cut. It may have been that the extra thickness helped too so i can't be definitive about it. I don't know if i would reccomend this though.:eek:

[Chuck Keysor]

Tom, maybe I missed it, but did you finish the back side of your lid the same way you finished the front? That is hugely important to minimizing your lid bowing. Though as I noted in the following examples, it will not eliminate the problem, but it may be a big part of it.

1) Dry quarter-sawn white oak won't necessarily eliminate your problem: I did some V-carving in a piece of quarter-sawn white oak, and had cupping similar to yours, though probably I had less. My stock was about the same size as yours, and I think it was 5/8" thick, with a bevel on the edge. The grain was perfectly vertical, and the wood had been in my attic for about 10 years as dimensional lumber. I brought it into my basement workshop, and let it acclimate for at least a week. It was close to flat before I even touched it, but I surfaced it and got it perfectly flat. But somewhere between the varnishing (which I did equally to all surfaces) and the time I did the V-carving, I developed a little bow. Each line of text was perfectly flat, but it bowed up, such that had I not re-zeroed the bit for each line of text, the middle line would have been too deep. Mine was just a wall hanging, and the bowing was slight, but even with dry, quarter-sawn white oak, this was still a problem.

2) Did you finish the back side of your lid the same as the front?:
I have a beautifully chip carved box that my grand father brought back from Europe right after WW2. The lid on that is 6 1/2" x 10" and 3/16" thick. That lid piece was attached to the edge of 4 vertical boards of the same thickness, to create the lid for the box. With that frame of the 4 boards to fight warping of the top, the top still warped, and even cracked the frame. In this case, the flaw I THINK, was that the back side of the lid was NOT painted or finished in anyway. That is a number one no-no.

Good luck, Chuck

[bleeth]

You can't take the cup out at this point, although if you carve a pocket in the back it might help, but don't count on it. If this is a relatively small box I would put it in a bench vise and hit the back with a hand plane to flatten it in a few minutes.
The issue is simply the nature of wood. A perfectly planed piece will change shape over time.

[Roy Harding]

If you've got the thickness to spare - use a jointer on the bottom face of the lid - then ensure that all six sides are finished the same.