Three-Legged Stool

By Rob Spiece March 7, 2024

Custom jigs ensure fool-proof production

Pictured left to right: Jed, Rob, Katie, and Isaiah

Illustrations: Christopher Mills

For a woodworking project that’s attractive, useful, and fun to build, it’s hard to beat this three-legged stool. With its scooped, gently triangulated seat, tapered legs, turned stretchers, and flared stance, it can easily find a home in most rooms or shops. In fact, because one stool is rarely enough, this project provides a great opportunity to jig up for small-scale production, as we’ve been doing for some time at Berea College Student Craft.

Making the jigs takes some time, but it pays off in spades. They ensure exacting joinery and enable you to make a set of stools in not much more time than it would take to make one without jigs. It also provides a great gateway into the kind of angled joinery and round mortise-and-tenon work used in chairmaking. Once you understand the concepts, it becomes a lot easier to translate those skills into seating designs of your own.

A project like this doesn’t cost a lot in the way of materials, especially when using domestic woods. We usually make the seat from cherry. Our legs and stretchers are usually made of ash or oak. Both are tough and inexpensive, with an open grain structure that is nicely highlighted by milk paint, which creates a striking and colorful contrast to the clear-finished seat. The seat wedges are walnut for additional contrast.

Make the seat

Begin by making two seat templates from 1/2” plywood or MDF, referring to the pattern shown. In the mortising template, drill small awl access holes at each mortise center point. Then make the seat blank from 5 / 4 stock. When making multiples, I dress a pair of 8 × 30” boards to 1-1/8” thick, with each length providing one half of two seats. After edge-gluing the boards together for a good grain match, rip the lengths to 14” wide, keeping the joint centered. Then crosscut each blank to 14” long. For each blank, mark the center point on both faces, and drill a 3/8”-dia. hole 1/4” deep into what will be the underside to create a pivot point for jig location. Bandsaw the blank round as shown.

Place the mortising template on the top side of the blank with its center line aligned with the blank’s grain direction. Then poke an awl through the template holes to locate the leg mortises on the blank. Using a drill press ramp as shown, bore a 1”-dia. hole at each location. Next, dish the seat using the jig shown, before moving back to the bandsaw to cut the final triangular profile that you’ve laid out on the underside of the blank using the shaping template. Afterward, sand the edges to remove any irregularities, and then round over the underside using a 3/4” roundover bit and the top side using a spokeshave. Finish up by plugging the center hole and sanding the bottom through 220 grit. Leave the top at 120 grit for now.

Seat pattern. This pattern provides reference for making two templates: one for the leg mortise locations, and one for shaping the seat. For the former, carry all the information shown onto the template except for the seat profile lines. Cut the latter template to the profile shown, and include the center hole. When laying out the shape of your seat, make sure to orient the template as shown here.

Circle-sawing jig. This jig ensures perfectly accurate bandsawn circles. It’s a simple sled outfitted with a runner that’s guided by the table slot, with a 3⁄8”-dia. dowel serving as a pivot point for the blank.

Leg mortise drilling ramp. This ramp locates the mortises for the legs perfectly equidistant from center and at precisely the same angle, ensuring consistent leg splay and interchangeability of parts.

Dishing jig. The curved rails on this jig allow a router on a sled to swoop down across the stool seat mounted on a dowel below. When constructing the jig, carefully lay out and pattern-rout the curved rails to ensure symmetry.

Make the seat

Seat round-up. Mount the blank on the jig, then slide it into the blade, stopping when the teeth are laterally aligned with the pivot point. This allows spinning the blank without deflecting the blade.

Foolproof mortising. With the seat blank on the drill press ramp, align the bit with a mortise center point, and clamp the ramp in place. Clamp the blank down, and drill the first hole. Rotate and repeat for the other mortises.

Controlled concavity. A plunge-router on a sled riding on curved rails dishes out the seat using a 5⁄8” straight bit. The seat blank underneath mounts on a central dowel, which allows rotating it for a series of overlapping cuts that terminate at the very edge of the circle. Make each cut in multiple passes including a very light final pass for best surface quality.

Roundover platform. Holding the shaped seat is tricky when rounding over the underside. To secure it, make a seat-shaped riser of 3⁄4” plywood with 3⁄4”-dia. dowels protruding upward at the seat mortise locations. Screw this riser to a base clamped to the bench. Round over the edges in several shallow passes.

A hand-made touch. Because of the dished surface, a router bit won’t work to round over the top. Instead, spokeshave the edge to a soft, graceful roundover.

Make the legs

At Berea College Student Craft, we make this stool in a 24” and a 26” (counter) height. To create the leg blanks, dress 8 / 4 stock into billets 1-3/4” square by 1” oversized in length (27” for a 26”-high stool). Then mark one blank for a 4-sided taper that extends from 1-3/4” square at the bottom to 1-1/8” square at the top. You’ll use this blank to set up your tapering jig(s). For efficiency, I use two separate fixed tapering jigs, but an adjustable jig will work too. You’ll taper a pair of adjacent faces on every leg first, then switch to your second fixed jig or reset an adjustable jig to saw the remaining two faces. Make sure to mark a bold × on each leg blank face to keep track of the cuts.

Next, chamfer the legs as shown, then cut the tenons on the top ends. An adjustable tenon cutter (See page 62.) is the perfect tool for production work. Because the tool can be difficult to maneuver in a hand drill, I built the very effective lathe-mounted tenoning sled shown. After setting up the jig, test the joint fit on scrap. It should be very tight at this point, barely fitting into a mortise. Finally, drill the mortise in each leg to accept its stretcher. Use a ramped jig on the drill press to establish the proper angle.

Tapering jig. This simple tapering jig has a fixed fence that is dedicated to tapering two adjacent faces of a leg. The jig fence aligns the taper waste with the edge of the base. A screw in the stop block registers against the leg’s trailing end while allowing sawdust to escape. The auto-adjust toggle clamp can be set to secure the leg at different thicknesses, and an integral handle keeps fingers safe.

Tenoning sled. This lathe-mounted tenoning jig consists of a box-shaped sled that attaches via drawer slides to a base, which is fixed to the lathe’s ways from underneath with a cleat. The sled directs the leg straight into the tenon cutter for accuracy. The overall dimensions of the jig suggested here are not critical; just make sure that the top of the sled sits 2” below the headstock center.

Stretcher mortise drilling ramp. This simple ramp made of 3⁄4” plywood holds the legs at the proper angle on the drill press to orient the stretcher mortises parallel to each other in the assembled stool.

Four-sided tapers. Begin by cutting two adjacent faces on each of the leg blanks. Then reset the jig fence (or use a separate fixed jig) to saw the remaining two adjacent tapers on all the blanks. Make sure to mark a bold × on each leg blank face to keep track of cut progress.

Easy chamfer job. Using a large chamfer bit at a router table, cut away the corners of each leg. Make sure to leave enough material at the top end for the full 1”-dia. tenon.

Tenoning on a lathe. This sled turns your lathe into a horizonal tenoner. Chuck a tenon cutter (inset) in the headstock and clamp the leg blank to the top of the platform. Cut the tenon with the lathe on.

Mortise for stretchers. Mark out the stretcher mortise 6” from the bottom of one leg and centered on its width, then mount the leg on the drilling ramp, position the ramp, and clamp it in place. Using a 5⁄8” Forstner bit, drill a 1”-deep mortise.

Stretchers

Mill some stretcher stock to 1-1/4” square, and then bevel-rip it into an octagon at the table saw. Next, measure for the main stretcher as shown, and create a blank that’s 1” over finished length. At mid-point, drill a 5/8” mortise, 1” deep for the cross-stretcher. Then turn the stretcher at the lathe, slightly chamfering the tenon ends to ease their fitting later. Dismount the piece and crosscut it to finished length. To ensure a perfect joint fit, I drive each tenon through a 5/8”-dia. hole drilled in a piece of stiff aluminum. To make the cross-stretcher, you’ll need a “dummy” main stretcher, like the one you just made but with looser tenons. Dry-fit it in place, and then repeat the same measuring and turning processes as for the main stretcher, but skipping the mid-point mortise.

Round joints: Tight makes right

Round mortise-and-tenon joinery isn’t nearly as strong as flat-faced joinery due to the limited long-grain to long-grain surface contact. Therefore, a tight fit is crucial to joint longevity. These stretcher joints should be snug enough that they can only be seated with confident hammer blows or direct clamping pressure.

Gauging stretcher length. After dry-fitting the legs into the seat, place two small sticks against each other, bottomed out in a pair of stretcher mortises. Then draw a reference line across the sticks. Remove them, realign the marks, and measure to establish your stretcher length.

A wrenching experience. When turning a stretcher from your oversized blank, begin by establishing the tenon lengths with parting cuts. Then turn them to finished diameter using a 5⁄8” open-end wrench as a gauge. Take care not to cut into the tenons when tapering the body.

Putting it all together

Mark the seat and the legs to register their orientation to each other, then bandsaw a 1”-deep kerf into the top of each leg. It’s important that the kerfs runs perpendicular to the grain of the seat to prevent splitting it when driving in the wedges during assembly. Saw the wedges from a 1 × 1” blank that’s wide enough for safe handling at the bandsaw. As shown, a bandsaw jig handles the job nicely.

Now you’re ready to put it all together. These tight-fitting joints won’t allow a lot of assembly time, so round up glue and tools and rehearse your procedures, dry-fitting the joints just deep enough to ensure they’ll seat successfully when glued. Assemble a stool in subsections as shown, coating mortises thoroughly but applying scant glue to the tenons. I clean up any squeeze-out with a damp toothbrush before moving on to the next step.

Slicing wedges. This simple bandsaw jig produces wedges quickly and accurately. It consists of a notched sled that rides atop a zero-clearance panel adjacent to the rip fence. A 1 × 1” wedge blank nestles in the 1⁄8”-wide × 1”-long tapered notch that carries it past the blade to slice off the wedges.

Stretchers together. After applying glue to the main stretcher mortise and one cross stretcher tenon, hold the parts square to each other while seating the cross stretcher in its mortise with firm mallet blows.

Initial stretcher seating. With one leg lying on the bench, hold the stretcher assembly in a “T” formation perpendicular to the leg, and glue and seat it firmly into its leg mortise with a mallet. Then glue-up the remaining two stretcher-to-leg joints, initially just seating them a little by hand, as shown here.

Set the splay and drive ‘em home. While the second two stretcher joints are only partially seated, align the legs with their seat mortises to achieve the proper angles. Maintaining those angles, then fully seat the joints with a mallet. Reorient the legs to their mortises during subsequent glue clean-up.

Seat the seat. After applying glue to the seat mortises and leg tenons, firmly drive the legs into their mortises until they stop at the tenon shoulders. Afterward, clean up any glue squeeze-out on the underside, and then invert the stool to install the wedges in their kerfs.

Locked legs. Tap the glued wedges in using a metal hammer while listening to the pitch. When the tapping starts thudding, you’ll know the wedge has seated.

Finishing up

After the glue dries, cut the protruding tenons flush to the seat. I find that using a flush-cut saw on this curved seat often results in scarring the surface, requiring scraping and sanding that can spoil the shape. Instead, I outfit a trim router with a circular auxiliary base made of 3/4” plywood, with an opening that’s wider than the tenon diameter. The small-diameter base of the trim router easily rides the seat curve, allowing me to rout the tenons nearly flush to the surface. Afterward, I sand through 220 grit.

The final step is to trim the bottoms of the legs to the same plane while leveling the stool. I first scribe for the cuts using a wood block drilled out to hold a pencil, guiding it along the benchtop around the bottom of each leg. After handsawing to my scribe lines, I chamfer the ends of the legs for a clean, finished look, then do one final touch-up sanding before applying finish.

Flush-trim trick. Use double-faced tape to attach a 3⁄4”-thick plywood ring to a trim router base, and adjust a straight bit just shy of the work surface. Nibble away the protruding tenon while running the bit clockwise around it.