Tenoning Jig

This essential workhorse is easy to build, accurate, and very efficient to use

Of all the jigs in a furniture maker’s arsenal, a tenoning jig is one of the most useful. It allows you to use your tablesaw to cut tenon cheeks, open-end mortises, spline slots, and other cuts that require standing workpieces on end.

Various commercial models are available, most of which ride in the saw table slots. Unfortunately, I’ve found the ones that I’ve used to be expensive, heavy, and somewhat clunky to adjust. I much prefer this shop-made version, which is designed to straddle the ubiquitous Biesemeyer-style rip fence found on most modern tablesaws.

Unlike the angle-adjustable fence on commercial models, the fence on this jig is fixed at 90°, but that’s fine for the vast majority of joints. In any case, you can outfit the opposite face of the jig with any additional fence configuration you like.

As shown in the drawing above, the jig design couldn’t be much simpler. What’s important is that the fence block is milled perfectly square, and that the face panels are dead-flat. When made properly, and fitted well to the rip fence, the jig produces terrifically accurate joinery. (Check out Twin Blade Joinery to see it in action.)

Faces first. Saw the face panels from 3⁄4"-thick MDF or hardwood plywood. (The MDF used here happened to have a maple veneer.) Clamp the faces to your rip fence, and mark a piece of 3⁄4"-thick plywood to fit between them to make the end panels.

Test for fit. Saw the end panels to size, and clamp them between the face panels to make sure the jig fits snugly on the fence, but slides easily without binding. If it’s too tight, shim it out by applying masking tape to the edges of the end panels. If it’s too loose, trim the edges.

Face panel layout. With face panels cut to size and butted together along their top edges, I mark the location of a carefully milled fence block on one face panel. This enables me to lay out the clearance holes for attaching it to the panel, and corresponding screwdriver access holes in the opposite face panel. Note that I’ve glued 1⁄4"-thick solid wood edging along the bottom edge of each face block. This enables me to joint the assembled unit square later (if necessary) without harming my jointer knives.

Drill clearance holes. Make one 1⁄32" oversize for fine adjustment. With the fence block clamped square to the panel, tap the screws to mark their centers, then bore the pilot holes on the drill press.

Assembly. Drill pilot holes and clearance holes, and then screw the face panels to the end panels, carefully aligning the top edges of the parts to keep the unit square.

Ready to work. With the jig straddling your rip fence, make sure the face panel sits square to the saw table (above). If necessary, run the unit across your jointer to square the bottom edges to the faces. Then screw the fence block in place square to the saw table. (The oversize clearance hole will allow adjustment.) Finally, attach a sacrificial fence to the fence block (right).