Single Blade Box Joint Jig Plans

I was really happy with the way the first version of this jig turned out, so when it was time to rebuild it in a more accurate and efficient way, I decided to film the process too. The results were great, pretty much perfect fitting box joints straight off of the tablesaw. I think this may be a really helpful jig for a lot of woodworkers like myself who have no dado set, but still want to create strong joints on the tablesaw very quickly.

How does it work? It works by having your work pieces clamp to a sliding fence which follows a cutting template. You make your cut, slide the fence over and make another cut. A ‘key’ limits the range of movement based on the cutting template you have setup. You are able to create multiple joint designs and cut them all out as easily as the standard one shown below.

The jig was made from scrap MDF, a short 2×4 offcut, and a small length of 19mm (3/4in) pine for the building blocks. It took just over an hour to make and cost me nothing, I had enough scraps on hand. It’s saved me a huge amount of time and money already; I’ve put together 6 drawers with it now, faster than ever before, and I didn’t have to use a single screw or purchase a dado stack to do so.

Click here to download the SketchUp file for this jig (compressed in a zip file)

Building the actual jig is fairly straight forward. I put it together using pocket holes to save time, but you can build it anyway you like. (My MDF did split in a couple of points but nowhere critical.) The plans have measurements in them but they are just a guide, they don’t need to be followed perfectly. Just build it to the size you require and to the stock you have on hand. I’ve used this version to make drawers that are around 1 meter in length. I cut all four sides at the one time, no issues at all.

The first step is simply making a sled with a 90 degree fence that slides on your tables mitre tracks. I used the 2×4 to provide strength, a platform for the joint building blocks and as a blade guard.

The most crucial part of the setup is the object you use as your ‘key’. The key is the part that registers against the joint blocks, limiting your movement. The key must be exactly the same size as the kerf that is left by your saw blade. Because the blade travels back and forth with the jig, if your key is off by 1mm, your joints will be 2mm off. If you are off by 2mm, your joints will be off by 4mm. It is super important that you find a key that is the same width as your kerf.

It took me 5 or 6 attempts to find the perfect key to use. I started with a screwdriver, then various screws and even an Allen key at one point. Eventually I used a bolt with the perfect diameter, which I drove right through the fence so that it wouldn’t wobble or waver. Don’t fret if your joints aren’t perfect at the start, just grab your callipers and look through your junk screw and bolt buckets for a better key.

The joint building blocks are the parts that create your cutting template. They are setup in what looks effectively like a castle turret style, one tall, one short, one tall, one short, etc. The leftmost piece is cut to fit in tightly and lock the rest in place. Literally use it to jam the rest in. This way the pieces are nice and tight for cutting, but can still be removed easily when you wish to change the joint design.

The key can move freely above a short block, but stops when it reaches the edge of a tall one. Once you have cut all of that block out, you lift the slider and key, travel to the next short block and continue cutting. This means that the width of your finger, will be whatever the width of your tall blocks are. The longer a key, the more chance it will wobble, use something short and stiff.

If you decide to make a different pattern than the traditional box joint, you can. You could cut joint building blocks from different thicknesses of wood for example. You could have a 19mm finger, then 9ml, then 19mm again for example. All of these can be cut using just the one blade and require no other setup once you have them jammed in place on the jig.

As for cutting, it’s pretty simple. You position two of your box sides to the sliding fence. Then offset the other two by the width of your first joint. This is easily done by cutting a building block to use as a spacer. Insert it the spacer, clamp it all up and then remove the spacer. Then make your cuts.

In writing, it seems like a lengthy process. If you watch my video you’ll see it actually takes no time at all. The jig is essentially always setup. Cutting 4 lengths of a drawer at once takes maybe a minute to clamp, 2 minutes to cut. Repeat that for the other 4 ends, and you are done in around 5 minutes.

What do you think? Be sure to leave me a comment here or on youtube with your thoughts. If you’ve made one or have improved the design, please let me know.

Disclaimer: I know it’s not better than a dado or stacked blade set. But I don’t have one of them. Feel free to send me a couple of hundred dollars and I will purchase a dado set and throw this jig away!