Make a table-saw box joint jig from a short piece of 3/4-inch plywood and a fitted hardwood indexing pin. Once you position the pin to match your blade kerf, the pin registers each cut so the fingers interlock. The method below follows David Picciuto’s Make: project; its example uses a standard blade to cut 1/8-inch fingers.
Choose a finger width and blade
Box joints, sometimes called finger joints, can be cut with a router or a table saw. This jig is designed for a table-saw sled or miter gauge. Choose the blade and finger width before making the jig, because the hardwood indexing pin must match the kerf.
| Choice | What it does |
|---|---|
| Standard table-saw blade | The Make: example uses a standard blade for 1/8-inch fingers. |
| Flat-kerf joinery blade | Recommended by the project author for a flat-bottomed cut. The author cautions that rip, crosscut, or combination blades may work but will not give the same clean, classic look. |
| Dado stack | An option when you want wider fingers; the example jig is set up around a 1/8-inch kerf, so size the pin to the cut you intend to make. |
For a balanced pattern, the project suggests making box height a multiple of the finger width so the edges do not end with partial fingers. Its sample box is 12 inches long, 9 inches wide, and 2 inches high, with two extra pieces for test cuts. Those are demonstration dimensions, not requirements.
Gather the jig materials and tools
The example jig blank is 3/4-inch plywood, 3 1/2 inches wide by 14 inches long. The author notes that blank length and width are not critical. The pin is made from hardwood, with glue to secure it.
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- Table saw and flat-kerf blade or dado stack
- Sled or miter gauge with a backing board
- Clamps
- 3/4-inch plywood and hardwood
- Wood glue or CA glue
- Sandpaper and an orbital or disc sander
Make the indexing jig
- Cut a kerf near the center of the plywood blank with the saw blade set 1/2 inch above the table.
- Prepare a hardwood strip 8 inches long, 1/2 inch high, and 1/8 inch wide for the example’s standard-blade setup. Test its fit in the kerf; it should fit snugly. Keep the blade and pin dimensions matched to the actual kerf you will use.
- Trim a 1 1/2-inch piece from the strip for the indexing pin. Glue it into the kerf, flush with the rear edge of the plywood. Keep the longer cutoff as a spacer for positioning the jig.
- Round the pin’s top lightly with sandpaper to help workpieces slide over it. The project author also suggests wax to reduce friction.
Position the jig and calibrate the fit
- Place the jig against the sled or miter-gauge backing board. Put the saved spacer between the saw blade and the pin so the pin is offset from the blade by one kerf.
- Clamp the jig in place. Make sure it is secure before cutting test pieces.
- Cut a test piece, then index the next cut by placing the previous kerf over the pin. Repeat to make a matching test piece and check whether the parts interlock.
- If the joint is loose, move the pin away from the blade. If it is tight, move the pin toward the blade. Make small adjustments, reclamp, and repeat the test. The project says an adjustment about the thickness of a business card should be enough.
A good fit interlocks without much force. Do not skip the test pieces: a small change in pin position affects every finger in the joint.
Cut matching box sides
- Mark the top edge of each of the four box pieces so you can keep their orientation consistent.
- Set blade height just above the thickness of the boards. This leaves the fingers slightly proud for sanding flush after glue-up.
- Cut both ends of each long side, keeping the top-edge marks toward the indexing pin as you make the cuts. After each cut, advance the board by fitting the previous kerf over the pin.
- Use a completed long side to establish the matching pattern on a short side. Keep the orientation marks facing inward toward the pin while cutting the mating sequence.
- Repeat for the other short side, then dry-fit the four pieces to check that the pattern closes and the joint fits.
Glue up and finish the box
Apply glue to the joints and assemble the sides. The project author notes that a correctly cut box self-squares; clamps can hold it together while the glue sets. Afterward, sand the proud fingers flush. Small gaps from blowout or chipped fibers can be filled with sawdust mixed with glue.
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Safety and project expectations
Clamp the jig to the sled or miter-gauge backing board, and keep each workpiece registered against the fence and pin. The project also suggests clamping and unclamping a board between cuts if you are uncomfortable holding it. These instructions are not a complete table-saw safety procedure: follow your saw manufacturer’s guidance and established shop safety practice for your equipment and operation.
Make: labels this project “Moderate,” estimates 1–3 hours, and lists a $51–$150 price range. These are the page’s own project estimates, not a current cost or independently measured build time. Picciuto also says that, after gaining experience, he can build another jig in about 15 minutes; that is his stated experience, not a general time estimate.
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Quick Recap
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