PROJECT: DIY Table Saw Tenoning Jig

PROJECT: DIY Table Saw Tenoning Jig

The cleanest way to cut tenons on a table saw is with workpieces standing vertically. To do it safely, you need a tenoning jig that holds parts upright and securely as you run them through the blade. The jig should also offer precise adjustability so you can cut tenons of many sizes and then trim them for a perfect fit in the mortise.

Adjustable tenoning jig in use on a table saw

This jig satisfies both goals in spades. Its upper carriage slides back and forth across the base on a pair of beveled guides, and the lateral travel is simple to fine-tune with a carriage bolt and knob in back. A toggle clamp and backstop anchors the workpiece. To save the backstop from blade carnage, I’ve added a replaceable strip that fits onto a sliding dovetail. All in all, it’s a must-have jig for any shop, so here’s how to build one for your saw.

Assembling the Base and Carrier Plate

Using paper shims as spacers when creating tenoning jig sliding guide
Screw one guide to the base, then slip a pair of paper shims between the other guide and the carrier plate before attaching the second guide. The shim space will ensure smooth sliding action.

Cut the base, carrier plate and guide strips (pieces 1 through 3) to size, following the Material List at right. Plow a 3/8″-deep dado along the length of the base that matches the width of your saw’s miter slots exactly — it will house a runner, later, that guides the jig. Drill a 5/16″-diameter bolt hole through the base at its centerpoint.

Routing hold-down bolt slot in tenoning jig
Rout a 2-1/4″-long slot through the carrier plate for the hold-down bolt. Use a 5/16″-diameter straight bit to mill this slot in a series of passes, raising the bit about 1/8″ with each pass.

Now, switch back to your standard blade, and tilt it to 20°. Bevel-cut the short ends of the carrier plate and one long edge of both guides. The Drawings will show you that the complementary bevels on these parts form a big sliding dovetail joint that holds the carrier plate against the base. Screw the guides to the base with the carrier plate in place, then shift the carrier over so one edge is flush with the edge of the base; we’ll call this the “front” edge. Extend the bolt hole in the base up through the plate. You’ve now created a starting point for routing a 2-1/4″-long slot toward the back of the carrier plate. The slot will house a carriage bolt and hold-down knob (pieces 4 and 5) that lock the carriage in place during tenoning operations. Step to your router table and complete that slot. Then, drill a 3/4″-diameter shallow counterbore into the bottom of the base to recess the carriage bolt head.

Next, follow the Drawings to make and attach two fence braces (pieces 6) to the carrier. Their 7-1/2″-long edges should be flush with its front edge. Slide this carriage assembly back onto the base. Cut and fasten the fence (piece 7) to the fence braces; align its bottom edge with the bottom of the base.

Installing the Carriage on the Base

Marking centerpoint for adding adjustment bolt to tenoning jig
Insert a 15/32″ bit through the hole in the support bracket to mark the centerpoint for the bolt that will move the carriage. Drill a 5/16″- diameter hole and bolt-head counterbore in the back block only.

Cut the support bracket (piece 8) to shape, and drill a 15/32″ through-hole where it’s indicated on the Drawings. Fasten the bracket to the top of the base right behind the guides. Now make up two bearing blocks (pieces 9). Slip them between the support bracket and the fence braces. These blocks will capture the head of the carriage bolt (piece 10) that moves the carriage back and forth.

Carriage bolt altered for attaching to tenoning jig
Grind or file away the flat areas under the carriage bolt head so it will turn freely in its counterbore.

Mark the centerpoint for this bolt hole by sticking your 15/32″ bit through the hole in the support bracket and pricking the back bearing block. This block receives a 5/16″ bolt hole and a counterbore for the bolt head (see Drawings). Drill those holes now.

Gluing adjustment bolt into bearing blocks of tenoning jig
Then capture it between the bearing blocks permanently with glue and screws.

The long carriage bolt will spin inside the bearing blocks if you grind or file off the “flats” under its head. When that’s done, fasten the front bearing block to the fence braces, slip the bolt through the rear block and glue and screw the two blocks together. I smeared a dollop of paste wax into the bolt head counterbore first, to help it twist easily.

Adding carriage bolt and knob to adjustable tenoning jig
A long carriage bolt and threaded insert provide the mechanical action that moves the carriage across the base. Lock the adjustment knob and jamb nut onto the bolt with two-part epoxy.

Your last step to installing the carriage is to screw a threaded insert (piece 11) into the support bracket hole you drilled earlier. Slide the carrier onto the base, and engage the carriage bolt and insert. Wind the bolt far enough through so you can spin on a jamb nut and the adjustment knob (pieces 12 and 13). Test the action of the carriage by turning the knob in both directions. If things work smoothly, remove the carriage, sand the parts and apply finish.

Finishing Touches

Routing a sliding dovetail on adjustable tenoning jig
Connect the edging strips and workpiece stop with a sliding dovetail joint, milled on the router table. Here, the author routs, then rips two edging strips from a wider piece of stock.

While the finish dries, make up the workpiece stop and edging strip (pieces 14 and 15). I routed a dovetail pin along the front edge of the stop and a corresponding dovetail slot in the edging strip so these parts fit together. Make up a bunch of edging strips while you’re at it — they’ll get chewed up by the blade during tenoning. You can trim off the damaged portion and reuse the edging several times, sliding it farther down the stop. When it gets too short to work properly, switch to a fresh strip.

Attaching adjustable tenoning jig to a table saw
Square up the workpiece stop to your saw table and tighten the knobs. Fasten a toggle clamp to it with short panhead screws.

Use a pair of carriage bolts and knobs (pieces 16) to mount the stop on the fence, and slide an edging strip into place. Wrap up your handy new tenoning jig with a hardwood runner (piece 17) for the miter slot — attach it with short screws driven down through the base. I used hard maple because it is so dense that it wears well in this sort of situation. Test the piece in the miter slot to be sure that it slides freely along the length of the slot. The last task that you have is to fasten a toggle clamp (piece 18) to the stop about midway along its length.

Once that work is done, you’re ready to start cutting tenons, safely and accurately, with your hands well away from the saw blade.

Click Here to Download Drawings and Materials List.

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