Perfect Box Joints - on a Small CNC

This is a project I've been thinking about for a while. I love the look of crisp box joints but have never been pleased with cutting them out by hand. I have a small CNC, however, making crisp corner joints with a CNC requires a jig of some kind. Simply cutting out pins and tails on a flat board will cause the inside corners to be rounded.

After a good amount of testing, I made a little jig that mounts on the end of my small 3040 CNC. The jig holds the wood vertical so the joint can be cut cleanly. The jig is explained in the video, but is simply a piece of square stock bolted to the end of the spoil board.

The other "trick" to making the cuts crisp is to make a pocket cut that is larger than the wood your're using. I used Inkscape to design the joint and then ran the tool paths through Jscut (www.jscut.org); both free programs.

The box joint came out very tight and clean. This opens up all kinds of possibilities for other projects too!

Video Link:

Thanks for taking a look!