Make a Stable Tabletop

Q:

I wanted a solid wood top for a small pub table. I used narrow oak boards that measured 8 percent moisture content and were acclimated to my shop. I glued and biscuit-joined the edges, and alternated the end-grain rings on adjacent boards. I then glued and screwed a 34 " plywood backer to the solid oak top to keep it flat and stable. Within two days after I stained it with water-based stain, the oak and plywood top had cupped a good 14 ".
—Wayne Oldenburg, Roscoe, Ill.

A:

Bonding plywood to solid stock was this top’s undoing, Wayne. That’s because solid wood and plywood expand and contract at different rates with changes in moisture content, as illustrated above.

Sometimes, simple is better when it comes to glue-ups.  Limit boards in your top to no more than 5" wide, and then plane stock to the thickness you want. Edge-glue the pieces and allow the glue to dry thoroughly before sanding the top.

Instead of using plywood to stabilize the top, attach it to the apron using fasteners that accommodate expansion, such as a figure-eight connector.

Oil-based stain will introduce less moisture to the wood, but you may still be able to use water-based stain if it’s removed promptly and not allowed to pool on the surface. Should the wood warp after staining, allow several days for the wood to dry again before proceeding.

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