Flattening A Warped Board

[daveq]

Please tell me if my information is not correct:

I have a warped quilted maple set (warped meaning both ends point upwards) and they are also cupped. The cupping is not a concern - I know how to deal with it.

If the boards weren't so wide, I could use my 6 inch jointer. I think the way to do it with that is to run the boards with the "U" shape pointing downwards - right?

Anyway, since the boards are wider than what my jointer can handle, I thought I would build a sled for my thickness planer. I ran one baord through with the "U" shape pointing upwards. It came out pretty nice. Not exactly flat but close enough where I can deal with it.

I tried using the sled for the other piece but I think I'm flexing it when it's being held in. When I take it off the sled, the warp returns.

So, am I going about this the right way? I have a little less than 1/4" of play left before I'm going to be in trouble so I don't know if I should continue messing with that sled.

Would I be better off using my 6" block plane? If you think it would work - what direction should I run the plane in? Do I start from the edges and work inward or do I start in the middle and work toward the edges? How would I clamp the board to keep it from moving without flexing it?

If I'm not being clear, please let me know. I may not have internet access until Sat. night so if I don't respond to questions, that's why. I should be able to check tonight though.

Thanks,

DaveQ

[bassman]

First of all... any time that you run a peice of cupped wood through a planer or joiner always place the concave face down, and convex upwards. Once you have a wide enough flat area on the convex side you can flip it over and do it the other way. The idea behind this is that the peice will not rock if two edges separated a distance.

You could put the peice through your planer on a sled like you already tried, yet put it in convex side up, also shim underneath the cup in the middle so that it cannot be pressed flat by the rollers... this should take care of the problem.

Peace and good luck,

Ryan

[Drak]

Well, my way to deal with warped boards (which I have quite often) is to liberally wet both sides and clamp the board between 2 harder and thicker and flatter boards, come back in a day or two, board is flat as a pancake, dry, and ready to work, and you don't lose any thickness.

You may already know this, but it's important to have both sides of your boards treated equally, i.e. if one side is sanded smooth with 220 grit, and the other side is still rough hewn, the rough hewn side will accept moisture faster than the sanded side and it will cup in towards the sanded side, so try to keep your boards treated equally on both sides FWIW.

Like, you said you planed one side of your board. If the other side is of a different texture than your planer treated the one side, it will still warp or cup or twist on you unless you clamp it flat or treat both sides equally.