Build a Table Saw Box Joint Jig

Perfect box joints depend on one thing above all else: accuracy.

Even a small amount of play in a jig or a slight error in the spacing between the blade and index key can turn a good-fitting box joint into one that's too loose or too tight.

That's the idea behind this Adjustable Box Joint Jig. Instead of continually compensating for variables in the setup, the jig is designed to eliminate as many of them as possible from the start.

Eliminate Play in the Box Joint Jig

Many box joint jigs attach to a table saw's miter gauge. The problem is that any play between the miter gauge bar and slot can affect the jig's position — and ultimately the fit of the joint.

This jig takes a different approach.

Instead of relying on the miter gauge, the sides of the jig act as runners and ride directly in both miter slots of the table saw.

Using both slots provides stable travel and prevents the jig from racking as it's moved across the saw.

The result is a solid platform designed to move through each cut consistently.

Removable Fences Make the Jig Adjustable

The runner system takes care of one potential source of error. The next challenge is indexing the individual box-joint cuts.

A traditional box joint jig often uses an adjustable index key. That works, but changing to another size of box joint means fine-tuning the relationship between the key and blade all over again.

This jig uses a different system.

The jig accepts removable fences, with each fence equipped with its own fixed index key for a particular box-joint size.

Rather than repeatedly adjusting one key, you can set up separate fences for the box-joint sizes you use.

Return to the Same Setup

Interchangeable fences wouldn't help much if you had to reposition them from scratch every time. That's where another small detail comes into play.

A stop at the end of the jig establishes the fence position. Remove a fence, reinstall it later, and the stop allows it to return to the same location.

This combination of fixed index keys, interchangeable fences, and a repeatable fence position eliminates much of the fine-tuning normally associated with changing box-joint sizes.

A Box Joint Jig Built Around Accuracy

There's nothing particularly complicated about the individual features of this jig. What makes the design work is how they function together.

The dual runners provide stable movement across the saw. The fixed index keys eliminate repeated key adjustments. And the removable fences and stop make it possible to return to an established setup.

Together, those features create a table saw jig designed to make accurate, repeatable box joints without starting the setup process from scratch every time.

Build the Adjustable Box Joint Jig

Ready to add one to your shop? The complete woodworking plan walks you through building the jig, removable fences, index-key system, and other details.

LEARN HOW TO MAKE BOX JOINTS → Get the Adjustable Box Joint Jig plans