Edge gluing basics

The first time I glued pieces of wood together along their edges was while building the top for a butler's tray tabletop. It was the first big project that I built to sell, but the instructions on the plans I was following didn't help much. “Glue enough wood together for the top,” it advised, “then sand.” That was it. One measly sentence. I spent more time figuring out how to get through that “simple” step than building the rest of the table. Successful edge-gluing always begins by planing and jointing neighbouring pieces of wood so that they're the same thickness and meet each other gap-free. But that's not all there is to edge-gluing success. A good deal more is required that doesn't get nearly as much attention-including three key techniques.

 

 

 

 

 

 

 

 

 

 

The biggest edge-gluing headache is dealing with board-to-board mismatch. Everything has to be perfectly flat when you're done building a door panel or a tabletop, and getting this result with the least amount of effort and sander time is the name of the game.

The biggest advantage you can give yourself is the technique you use to clamp boards together while gluing. Even if your boards are the same thickness and meet each other gap-free (and they should), a little warping can still cause a lot of trouble. That's why I recommend clamping in three steps.

For step 1, begin by lining up boards (with glue on their edges) on a series of pipe clamps spaced 12" to 14" apart. Tighten them up until the boards begin to come together, then stop. Next, gently tighten some medium-size C-clamps over the joints at both ends of the assembly. This levels up the ends of the boards and holds them that way.

For step 2, push down on any boards that might have been bowed upward as you tightened the main clamps. Board-to-board joints should be quite flat by now, with less then 1/16" of difference between them.

Finally, step 3: Tighten a few more pipe clamps over the top of the assembly, between the ones underneath. This third step directs clamping pressure downward in a way that prevents the boards from arcing upward.

Illustration by Paul Perreault

If you own a thickness planer, there's an edge-gluing trick that will save you most of the trouble of evening up irregular joints. Glue your boards together in two stages, with these first assemblies as wide as your planer will take. When the glue has dried, feed these subassemblies through the machine to level everything up mechanically while it's easy. Only afterward do you complete the final gluing. This approach minimizes the levelling required with handheld sanders. Just remember to remove all hardened glue from the boards before you feed them through the planer to avoid chipping the blades.

If, after all this, you still have some glued boards with steps between them, use your belt sander on the cross-grain with an 80-grit belt. This removes wood quicker than sanding along the grain and yields flatter panels. When the joints are levelled, sand parallel with the grain to remove the scratches.

The best woodworkers are good at edge-gluing solid wood because the results play a large role in project success. You've probably noticed that success depends on understanding a few techniques that aren't always explained as fully as they should be. But no matter. Now you're the kind of woodworker who knows the tricks.