Q: I have been using biscuits to edge join stock when making the panels for my projects. With the excellent glues available today, I wonder if the extra step of using biscuits is necessary. My question, then: When is it necessary to use biscuits in edge joining and when is regular gluing sufficient?
A: While you can almost never go wrong adding a biscuit to a joint, I’ve found from talking to woodworkers in my classes that biscuits are often overused. In an edge-to-edge glue-up, such as for a raised panel or tabletop, two well-jointed edges with adequate glue will create a joint stronger than the surrounding material, even without a biscuit. When I taught woodworking with the Peace Corps in Africa, the kids would hand plane edges, apply glue and, because we didn’t have bar clamps, simply rub the two edges together and lean the assembly gently against a wall. By the next morning, the glue-up was rock-solid: a great testimony to nice straight edges and good glue.
My number one reason for adding biscuits to an edge-to-edge glue-up is registration. Biscuits keep the faces of the boards aligned as you close the clamps — helpful on a large glue-up.
It’s also a huge benefit when working with a solid wood to plywood combination, such as when a solid-wood band is used to cover the edge of a plywood shelf. Good alignment means less sanding, which means less chance of sanding through veneer.