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My simple tenoning jig produces flawless tenons in minutes— even haunched tenons. The jig consists of a sled with a glued-on support block and a screwed-on sacrificial backstop. The sled and support block are flush on the work side and square. The backstop protrudes by the thickness of the workpiece, minus 1/16-in.
Before using the jig, install a spiral bit and set its height to the tenon’s length. Position the fence and clamp a spacer that’s the same thickness as the workpiece against the outfeed end.
To rout the tenon cheeks, clamp the workpiece flush against the jig’s support block and backstop. Then rout from right to left, while pressing the sled against the outfeed spacer and the workpiece against the infeed fence (above). I usually make a light scoring pass before routing full-depth: I bear the sled against the spacer, but pull the workpiece away from the fence and guide it freehand through the cut.
To rout the tenon ends, I install the workpiece behind the stop. To create a haunch (picture above), I place an appropriately-thick shim beneath the workpiece before I clamp it to the stop. –Joseph Scharle
