Kerf and Wedge a Twisted Board Flat Before It Meets the Jointer

The Problem

A board with real twist is a jointer's worst customer: to get one flat face, the machine has to cut down to the lowest point of the twist, and everything above that becomes chips. On a badly wound board that can mean losing a centimeter of thickness — a board bought as eight-quarter effectively becomes five-quarter, and sometimes the flat board left over is too thin for the part it was meant to be.

The Technique

This furniture maker relieves the twist before flattening instead of machining through it:

1. Rip a kerf down the middle of the board's length — about two-thirds of the way through its thickness. The kerf lets the two halves of the board move independently, releasing most of the twist's spring.
2. Clamp the board dead flat to the workbench so it lies fully seated along its bottom face.
3. Measure the kerf's width and depth as it sits clamped open, and cut a wedge-strip to match.
4. Glue the wedge into the kerf and leave it clamped until dry. The wedge locks the board in its flattened state.
5. Joint and thickness-plane as usual — the board now needs only cleanup passes, not a full de-twisting, so the material loss is a fraction of what brute-force flattening costs.

His comparison on the same stock: conventional jointing would have eaten a full centimeter; the kerfed board cleaned up losing far less.