Reply To: Resawing and cup

#766739
Edmund
Participant

I have trouble producing 1/4″ to 3/8″ thick material when resawing because of cupping. A common situation is to start with 4/4 rough and try to produce two 3/8 thick pieces. Right now, I need to make a pair of pieces 3/8″ thick that are 10″ x 20″ by resawing some 6/4 walnut. The material is plain sawn with some rift on the edges.

In the past, I’d hand plane a surface flat and then resaw. Since the cupping comes from both moisture and tension, I’m wondering if I should try something different and plane *both* faces some amount before resawing. That way, all 4 faces are fresh rather than producing one board with two fresh faces (newly jointed plus newly resawn faces) and one board with one fresh face (from reseawing) and one original rough face. Would that help? Since both halves will cup, usually, I suspect this isn’t going to help much.

Usually, I take as little off of the thickness as possible before resawing to give myself material to flatten after the cupping. Is that a mistake? Should I be taking a heavy amount off of each face trying to get rid of the faces exposed during drying?

Any suggestions / tricks? I’ve done the “cut fat and sneak up on it over days” trick many times. For 1/4″ and 3/8″ final, it hasn’t been reliable. Getting wide quatersawn isn’t really an option.

Hey Ed! Sorry to hear about your troubles. IDK if you listen to the Fine Woodworking podcast, but Mike Peckovich recently addressed this exact issue, and his answer sounded to me a lot like your thoughts.

My recollection is that he said re-sawing 4/4 material is a train wreck of cup/twist/bow/etc, and it’s simply a non-starter for him. He acknowledged with some exceptionally well-behaved stock it is absolutely possible, or with less-than-perfectly-behaved stock there are some tricks with moisture and stickering and weights and etc, etc, that can be employed, but on average, he doesn’t look to 4/4 material.

He said to get thin slices that don’t go crazy, start with properly-dried, 8/4 stock (or thicker), and take your slices from opposing sides. Obviously the outsides will be much closer to (or at) equilibrium moisture content, and in his experience, there is much greater stability in the resulting boards.

It was, I think, in one of the most recent 2 episodes. I’d start with episode STL268 (I won’t include the Youtube link because this site often mis-identifies replies as containing spam if you simply link to other woodworking content, but just go to the Fine Woodworking channel on YT and search for STL268) and if it’s not there, try STL269. Get the info straight from the source in case I’m mis-remembering something.

Good luck!