To obtain the thickest true lumber from cupped rough stock, which procedure is recommended?

• A. Rip the rough stock, then face the pieces cupped upside down on a jointer
• B. Face the cupped pieces upside down on a jointer after ripping
• C. Joint the pieces to remove cupping
• D. Use a thickness planer on the cupped side

Answer: (A)

The important idea is how to turn cupped rough stock into true, thick lumber by using the right sequence and the right tool orientation. To keep as much thickness as possible while making the board true, you want a flat reference face and a straight edge, then you flatten the opposite face without excessive material removal. Ripping first gives you workable, straight edges to feed and supports good control on the jointer. By placing the cupped face down on the jointer and running the piece, the cutter shaves a flat surface on the opposite face, while the cupped face becomes the reference that remains in contact with the bed. This minimizes how much material you have to remove and yields a board with flat, parallel faces and square edges, which is what “true lumber” means in practice.

Using a thickness planer on the cupped side would not reliably flatten across the width and can waste material or leave uneven thickness. Jointing to remove cupping without addressing the overall planing can also waste more stock and fail to produce two stable, parallel faces. So the best approach is ripping first, then face the cupped stock on the jointer with the cupped face down to establish a true surface while preserving thickness.