Cut out cupping


I would like to make a box with a top that’s 13" wide using a 14"-wide mahogany board. Will there be a problem using a single board for the top?
—Jim Curtis, Longboat Key, Fla.


A board that wide will most likely cup unless the grain is riftsawn or preferably quartersawn, Jim. Imagine the end grain’s growth rings as curved bands under tension to straighten out. The wider the board and the more the grain runs parallel to the surface, the more likely that tension will be released with time or after you joint and plane the pieces. For a panel as wide as your box top, we prefer to glue-up boards no wider than 5" and preferably 4". If there’s a riftsawn or quartersawn grain section at the edges of your 14" boards, cut away the flatsawn cathedral-grain section and edge-glue the straight-grained pieces.

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