Jigs make mortising a snap
A set of simple jigs aligns with the mortise layout marks for quick and accurate routing of the leg mortises. For the mortises on the faces of the legs, make a mirrored pair of jigs: one for the back left and front right legs; the other for the back right and front left.
For each jig, glue up four pieces of 3⁄4" plywood, leaving a 21⁄2"-long slot in the center [Jig Drawings]. Mark centerlines on the top of all three jigs and extend them down the inside edges of the slots to make it easier to line up the jig with the centerlines on your workpieces. Cut the cleat for each jig, but don’t attach them just yet.
Clamp one of the face-mortising jigs to the inside face of a back right leg, lining up the jig centerlines with those of the mortise. Place a strip of double-faced tape on one of the cleats and attach it to the underside of the jig butted up against the edge of the leg [Photo,
below]. Unclamp the jig from the leg and drive a couple of screws through the cleat to secure it. Label the jig according to which legs you’ll use it with. Repeat the process for the other jig, but using a back left leg.
To rout the mortises on the edges of the legs, screw (don’t glue) a cleat vertically to the edge/end-mortising jig, 3⁄32" from the edge of the slot. Use the same jig later to rout the mortises for the back by simply repositioning the cleat [Edge/End-Mortising Jig Drawing].
Tie it all together
1 Cut the rails (C, D) to size [Materials List, Exploded View]. Bevel the ends of the side rails (C), then lay out centered mortises on the ends [Drawing 3, Exploded View]. Cut the splats (E), but don’t taper the edges yet.
2 Using the edge/end-mortising jig, rout mortises in both ends of the rails (C, D) and one end of each splat (E) [Exploded View].
3 From 10/4 stock, cut blanks for the crest rails (F). Lay out the rail profile and the mortise on each blank [Drawing 4].
4 Reposition the cleat on the edge/endmortising jig and attach it to rout the mortises in the crest-rail blanks. Bandsaw the crest rails to rough shape, beginning with the front profile and then the top profile [Drawing 4]. Sand the rails to final shape.
5 Cut two 3⁄8×21⁄4×20" blanks for the loose tenons (one blank per chair). Rout 3⁄16" round-overs on the edges and cut 111⁄16"-long tenons from the blank [Exploded View].
6 Dry-assemble the chairs, and scribe the curve of the crest rail (F) onto the top of the back legs (A) [Photo G]. Extend the marks down the faces of the legs [Drawing 1].
Set the splats and crest rails aside for now. 7 With the table tilted, bandsaw a notch for the crest rail in each right back leg, stopping at the layout line [Photo H]. Tilt the table in the opposite direction and cut a notch in the facing legs. Cut the end of each notch [Photo I].
8 Round over the legs where shown [Drawing 3]. Finish-sand the legs and rails, and assemble the sides [Photo J]. With the glue dry, glue the front and back stretchers (D) between the side assemblies.