Making the spacer boards a few thousandths wider than the router bit would increase the width of the pin, but the router bit and it's cut would remain the same size, so the joint would become tighter, or not fit at all. Reducing the width of the spacer boards by a few thousandths of an inch would narrow the pins and the router bit cut would remain the same width, so this should work, if all of your spacer boards are exactly the same width and just a few thousandths smaller than 2X the size of the router bit. The joints won't need to be pounded together, and there will be just enough room for the glue.
Notice how the work pieces all seem to have been glued together before cutting too. He had to pull them apart before he could assemble them. This is actually a good idea to keep them from moving during the cutting. I'm wondering what the glue choice was, since they were so easily pulled apart after cutting.
Watch the video closely and you will see that the spacer boards are being added between the fence and the work for each of his passes. I have tried this method, and much prefer my Incra I-Box jig on my Unisaw with Freud SBOX8 blade set for making easy and repeatable box joints with nearly no tear-out. You will notice that he doesn't show the back side of his cuts. All you can see is the front side of the work pieces, and he is using pine, a very soft and flexible wood.
I just completed making some "Apple Boxes" from Baltic Birch plywood late yesterday. This is the movie industry name for them. They were made to be used in my photo/video studio. With the capability of making them in my shop, I was not about to pay $2-300 for a set of them, and I made 2 sets for 1/3 of the out-of-pocket cost of 1 purchased set of poorly made and nailed together "Apple Boxes". All of mine, except the 1" high, have box jointed corners that were made using my Incra I-Box jig on my Unisaw, using a Freud SBOX8 blade set to make the 3/8" box joints and all of the joints are very clean with no tear-out. I'll post photos and more detailed information about these boxes later today in a new thread.
He isn't one of the more safety minded woodworkers either. I cringed when I saw him hand feeding the boards through his sliding table saw.
Central North Carolina
Last edited by CharleyL; 04-30-2020 at 10:24 AM.