A woodworker wants advice about how to biscuit join a skirt to a table top to achieve perfect alignment. He wonders if he should cut a slot for a #20 but use a #10 to allow for movement?
Ellis Walentine: I don’t recommend using biscuits to attach tops to tables. Not only is it tough to line things up, there’s no way to allow for movement, unless the top is so small or narrow that you don’t expect much movement. Plus, there’s no way to remove the top if you ever need to for any reason.
If you’re itching to use your biscuit joiner, use it to saw slots every foot or so around the inside perimeter of the apron and make some hardwood button blocks with tabs that fit in the biscuit slots. Make the shoulders of the button blocks a little shorter than the spacing of the slots from the top of the rails, so that when you screw down the blocks, the tabs pull the tabletop tightly to the apron assembly.
Rob Johnstone: Without seeing the table, it is a little difficult to answer. My favorite way to join a skirt to a table top is with table top fasteners. They’re little pieces of hardware that use a kerf sliced into the skirt and an L shaped metal tab, which is then screwed into the table top. The L of the tab is inserted into the kerf and holds the top tight. I would not use a small biscuit in a larger opening, as it works against the design of a biscuit joint.