Gluing up box joints can be a tedious job, but there are a few things you can do to make the task easier. The first is making sure the joint fits together well. Joints that are cut properly should come together smoothly. The big advantage of box joints is the large amount of gluing surface the interlocking fingers create. So it only takes a small amount of glue to create a rock-solid joint. In fact you don’t need to put glue on every surface. I like to use an acid flux brush to apply a small amount of glue to the top of each finger. As you assemble the joint, glue spreads to other surfaces. But there are a couple of ways to control it. You can place masking tape next to the pins before you glue. This will trap any squeezeout on the inside corners where it’s tough to get at.
Then just pull it off with the tape after it’s skinned over and it’s easiest to remove. Also, lightly sanding the ends of the fingers with 220-grit sandpaper will help keep glue from seeping into the end grain where it’s more difficult to remove. Another option is to cut the fingers slightly longer. This way when you trim them flush, any excess glue is removed.
The last step to success in making a perfect box joint is clamping. This can be a little tricky, but there is a step to take to make it easier. If the fingers stand proud of the sides, as I mentioned earlier, you can’t really apply clamps directly on the corners to pull them tight. The answer is to use clamping blocks positioned near the joints. (For small projects that don’t require much pressure, you can wrap a band clamp around the whole assembly.)
