How do I build a flat, stable tabletop?
I am building a tabletop and wondering if I should alternate the boards' growth rings so the top remains stable. Also, should I use 6" boards and narrower, or is it okay to use 8" boards?
—Nancy Southall, Baltimore, Md.
For stability, alternating the direction of the growth rings helps but matters less than choosing your grain carefully, Nancy. Straight-grained riftsawn or quartersawn wood proves more stable than flatsawn, cathedral-grain patterns. Start with properly dried wood and let it acclimate to your shop for a couple weeks before machining.
Likewise, the width of the planks won't affect the stability of a glue-up if you've chosen your grain carefully. (Keep in mind, though, that the wider the board, the more likelihood it will contain a mixture of stable riftsawn and warp-prone flatsawn wood; see photo). When you are able to acquire ideal, wide expanses of stable grain, you can size the boards for aesthetics and for the capacity of your machines. For instance, if you have a 6" jointer and a 12" planer, 53⁄4 " boards allow you to glue up sub-panels that won't exceed your machines' capacities. If you prefer flatsawn grain pattern or are unable to work around it, 4" or less serves as a good rule-of-thumb board width for a stable glue-up.