How to Make a Box Joint Jig
Take your woodworking to the next level with this simple jig. All you need are some miter gauges, plywood and careful measuring.
An hour or less
Less than $20
IntroductionTake your woodworking to the next level with this simple jig. All you need are some miter gauges, plywood and careful measuring.
- dado stack
- Miter gauges
- Table saw
- 3/4-in. plywood
Set Up Tips
- The blade setup determines how deep the pins and sockets are on your joint. Box joints look best when they are cut to match the thickness of your stock.
- Make a test joint before cutting into the material you plan on using for your enclosure. Your jig will likely have to be fine-tuned after its initial setup.
- Using a framing square, check that the blade is 90-degrees to the tabletop and 90-degrees to the miter gauge sled.
- If the joint is too loose, the pins are too small, so make the space between the blade and the peg bigger by sliding the jig along the fence, moving the peg away from the blade.
- If the joint is too tight, make the pins smaller by sliding the jig to move the peg closer to the blade.
Project step-by-step (4)
Set up the dado stack
Set the dado blade height a hair taller than the thickness of your material. The dado blade should be stacked to 1/2-in. thick to match the width of the peg stock.
Building the box jig
Before you start, be sure all your parts are cut to size and then swap your table saw blade to a correctly-sized dado stack. This includes trimming the square stock to the exact same width as the dado stack for the peg. This post is written for 1/2-in. x 1/2-in. notches in 1/2-in. thick stock.
With the miter gauges in the miter slots, fasten the fence through the back of the miter gauges with 1-1/4-in. screws to make a sled. Clamp the second piece of plywood flat against the fence and push this setup through the dado blade. Unclamp the piece of plywood and glue a 2-in. length of 1/2-in. square stock (remember to match to your specific dimension) into the cut you just made. Create a space between the peg and the blade using the remainder of the 1/2-in. stock; this makes the pins and sockets the same size. Clamp the jig to the miter gauge sled.
This is an incredibly important step, so be careful to avoid mistakes that could ruin your project.
How to Make Box Joints: Making the cuts
With the jig adjusted, make a test joint to check the fit. The initial adjustment may need to be dialed in to get the fit nice and snug. If the joint is loose, the pins are too small (slide the peg away from the blade). If they don’t fit, they are too big (slide the toward the edge of a top/bottom part flat to the table and against the peg and make a pass. Make a reference mark on the front and back of this pin to help set up the cuts, fit the socket over the peg, hold it in place and make each pass slowly.
Box Joint Jig: Cut the inverse sockets
Flip the first board to the other side of the peg so the reference pin is between the peg and the blade. Push the edges together and make the rest of the cuts.