Join Date: Jan 2019
Location: Central North Carolina
I make a lot of boxes and usually just use clamps to pull the joints together and square up the box, but this only works well when the boards are flat. I don't use cauls, just Bessey clamps for pulling the joints together during glue-up. The box then just gets left to dry. I might check it to assure that all joints are tight and the box is remaining square, but there is no need to leave the clamps on after the glue is setting up. It's easy to box the box sides from too much clamp pressure, so there is benefit to not leaving them on, as long as the wood is flat.
I use an Incra I-Box jig on my table saw to cut my box joints, because I've found that I get the best results, and mostly use a Freud SBOX8 blade set, cutting 1/4 & 3/8 joints, but also a 1/8" FTG (flat tooth grind) blade that I use for 1/8" box joints. I have used my dado blade set for larger box joints, but don't need to do this very often. They don't have as clean and flat of a bottom in the cut, but for larger joints this isn't as obvious. It's very important to move the sacrificial strip in the I-Box jig to a new position just before you begin cutting the joints with the jig. This will minimize tear-out of the edges of the cut. This strip can be used many times and even inverted to the second edge before it needs replacing. I used the original as a pattern and cut about 16 duplicates from a 2' X 4' piece of 1/4" MDF, so I have enough to last me a very long while at a cost of about $6.
Most of my boxes are made from Baltic Birch plywood. I was once told "you can't cut box joints in plywood", but using the combination of the I-Box jig and Freud blade set above I have no problem, as evidenced by the attached photos.
Last edited by CharleyL; 09-23-2019 at 03:48 PM.