Box joints add flair to your cabinet boxes and give them a professional look. It’s relatively easy to make a simple box joint jig that clamps to a Dado sled and get great looking and consistent results.
Some Useful Tools to Help with this Build – Digital Calipers and Setup Blocks
Here’s how we built ours!
1. Determine the Size of the Box Joints.
We used 1/2-inch. We bought a fancy Diablo dado set and put on the correct combination of blades to get a 1/2-inch cut. We then set the height of the dado blade teeth (with the saw unplugged) to match the thickness of our materials which was 1/2-inch. We ran an uncut piece of wood that would form the guide through the dado stack until we had the correct height.
2. Cut A Box Joint Guide
I took a piece of red oak that I had lying around and cut it down to be the exact height and width of my box joint the dado blade would cut – this involved swapping the blades and throat plate. I bought a set of fancy calipers to help get these measurements right as a few 1000’s of an inch mattered. You could buy machined blocks to save yourself some time and fuss with the spacers provided in a good dado stack to get the widths to be the same. We made a long piece and cut it in half.
3. Install the Guide
We carefully nailed and glued one of the pieces we made into the groove created by the dado – this is the dado jig guide. We then placed the other piece to the right of the dado stack and used it to set the distance from the blade for the jig and clamped it into place.
4. Test and Adjust if Needed
We ran a few scrap pieces of the same material we were using for the drawer boxes through the dado stack and measured using the caliper. We adjusted as needed and kept at it until we got the results we needed.
TIP: Here’s a trick to adjust your box joint spacing on your jig in small increments. You can use playing cards to help you adjust your jig distance in small increments – a playing card is 0.17 mm or 0.0067 inches thick. Place the playing cards against your jig clamped to your back sled brace and clamp a piece of wood to hold them in place. Unclamp the jig, remove the playing cards, and slide it over against the clamped block. Reclamp the jig and test your cuts.
