Thickness Sanding Warped

[sgodbe]

I have a walnut bookmatched back that I need to thickness sand/plane. I don't have a drum sander, usually use the Wagner Safe-T-Planer. The pieces are a bit warped, and I wonder if I should try and flatten before planing, or plane through the warp. Fear abounds. Plane through the warp may result in way too thin sections. Whaddya think?

[Joey Herscovitch]

Unless they are thick enough to remove enough material to flatten them I would definately not plane through the warp. If the warp is slight then the back braces you glue in should hold them flat, or actually curved. You could actually use the warp in the direction you would normally arch your back. Anyway, at the finished thickness of the back the pieces should easily conform to your braces & hold its shape.

[Mark Dobbins]

try ironing the boards with your clothes iron to flatten then clamp between two boards to cool

[sgodbe]

Mark, thanks for the idea. I'll use my heating blanket and a board sandwich clamped down.

[FRANK]

ARE YOU IN CA I HAVE A PLANER AND 24INCH GRIZZLY SANDER

[sgodbe]

I'm in WA. Thanks for the offer. This morning, Rockler had an obscene sale on a 12.5" benchtop planer for $99. I'm gonna flatten the warp using my silicon heating blanket, clamped between two thick boards, then try the new planer. Thanks Mark for the idea of heating to flatten, and thanks Paul for the offer.

Do you love your grizzly sander?

[Matt Hayden]

Another thought - if the pieces are warped, the convex side is likely more damp than the concave side. Maybe you could dampen the concave side and see if the pieces flatten out....I've done that more than once.

[Bob Webster]

Yeah, Matt. At least get it flat for the amount of time it takes to thickness it. Roy McAlister, a master luthier here in Gig Harbor and former Chief Designer for Santa Cruz Guitars, has an appealing method if you have a concrete garage or shop floor handy.

Roy places the warped piece cup side down directly on the concrete, puts a piece of plywood over it, and then about 50lbs of whatever on the plywood and leaves it for a week or so. Swears by it. It seems that moisture is easily transported in the concrete. I wouldn't load it up fully immediately if the wood is really badly cupped Brazilian or some other really splitty stuff just because you might break it. However, the walnut should be just fine.

Cheers,
Bob

[sgodbe]

Bob, the walnut is now on the concrete floor and will sit for at least a week. I'll let you know the results.

[sgodbe]

Your suggestion worked beautifully. The warp wasn't relieved 100%, but flat enough now to rejoint, glue up and add the bracing. Thanks for the suggestion.