Box joints are the savvy woodworker’s alternative to dovetails. Strong, great-looking and quickly made, box joints are an especially good choice when you have a large number of items to produce. To make them, you need your tablesaw, a miter gauge, a dado set and a simple shop-made jig (Fig. A, below). I’ll show you how to build the jig and use its micro-adjust system to dial in perfect-fitting box joints.

Box joints have alternating pins and sockets. To fit together, one piece has pins where the mating piece has sockets (Fig. B, page, 70). The challenge is to cut pins and sockets that are virtually the same size, with paper-thin tolerances for fitting the joint. Fortunately, the jig can make paper-thin adjustments. It also automatically positions both pieces so their pins and sockets are correctly offset.

Design Details

Pins and sockets can be wide or narrow to suit your project. To size them appropriately, you merely adjust the width of the dado set. For example, to cut 1/4-in.-wide pins and sockets, use a 1/4-in.-wide dado set. The blade’s height determines the length of the pins and sockets. This length matches the thickness of your box pieces. Flat-bottomed dadoes are a must for good-looking joints.

It’s best to start with your box pieces oversize and trim them to final width after you cut and fit the joints. Box joints usually turn out to be wider than the sum of the pin and socket widths because of the fit-tolerance between each pin and socket. Starting oversize allows you to compensate.

Photo 1: Set the blade height using a piece from your project. Place the piece on the jig’s carriage and raise the blade.

A scrap piece held on top tells you when the blade is exactly even with the workpiece. Before moving on to the next step, make sure the miter gauge bar slides smoothly without any side-to-side play.

Photo 2: Clamp the adjustable fence temporarily to the carriage and cut a slot through both pieces. After cutting, thickness-plane a 12-in.-long piece to exactly fit the slots’ width. Cut this piece into three keys. Trim one key to two-thirds the size of the slot’s height.

Photo 3: Use three hardwood keys to position the adjustable fence on the carriage. Glue one key in the fence slot. Fit the second key in the carriage slot and sandwich the spacer key in between. Securely clamp the fence to the carriage while butting the three keys snugly together. Drill pilot holes and fasten the fence. Remove the clamps and the two temporary keys.

Photo 4: Micro-adjust blocks allow you to fine-tune the jig by paper-thin amounts. Attach one block to the carriage base. Butt the second block against the first, with two pieces of paper between them. Fasten this block to the adjustable fence. The space between the carriage bloc...

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