The seat of a sack-back Windsor chair is best cut from a single plank. As shown in the photo at left, the blank is roughed out by hand with a frame saw or bowsaw. Then the seat is given its basic shape using a variety of hand tools—the edges are rounded over by a drawknife (page 85), the top surface is scooped out with an adze and an inshave (page 86), and some final touches are etched with a veiner (page 87).
The final step is to bore mortises into the seat for the legs, spindles, and arm posts (page 90). As shown in the anatomy illustration below, the arm post mortises are the largest: / inch in diameter; the leg mortises are / inch in diameter, while the spindle mortises must be drilled with a H-inch-diameter bit. Refer to the diagram for the seat’s dimensions and for the location and spacing of the mortises.
1 Outlining the top surface of the seat
Saw your seat blank from a piece of 2-inch-thick pine (page 84), then outline the area to be scooped out. Start by marking the center of the blank’s front edge. Next, mark a line 2% inches in from each side of the blank; the lines should be parallel to the front edge and 43/ inches away from it. Draw a curved line that joins the two side marks and parallels the sides and back edge of the blank (left). Finally, draw two curved lines that connect the side marks and the center mark at the front edge of the blank; these lines indicate where the top surface of the seat slopes toward the front edge and are represented by the dotted lines in the illustration.
Clamp the blank in a vise and use a drawknife to round over its edges. To begin, smooth the circumference of the blank and round over its underside, pulling the drawknife with the grain (above, left)-, reposition the blank in the vise as necessary. If you
encounter a knot in the wood, cut around it gradually, rather than trying to hack through it with a single stroke. Then use the drawknife to form the flat lip on the top surface along the front edge of the blank, angling the cut at about 40° (above, right).
4 Smoothing the seat
Secure the seat between two bench dogs on your workbench, protecting the sides with wood pads. Start with an inshave to smooth the rough surface left by the adze. Working from one side of the top surface to the other, hold the inshave with both hands and pull it toward you; always follow the grain (right). Use a convex spokeshave, or travisher, to refine the smoothness of the seat (photo, page 71).
Dishing out the seat
Once the circumference of the seat has been shaped, rough out the waste from the top surface using a gutter adze. Wearing steel-toed boots, step on the edges of the blank to hold it steady and chop out the sitting area from one side of the outline to the other (left). Try to cut with the grain, using short strokes. Make sure your feet are not in the path of the blade. Continue until you have cut about % inch deep in the center of the seat with a gradual slope from the center up to the sides and front and back edges.
5 Shaping the lip
The lip at the front edge of the seat has a slight downward bevel. Working on one side of the seat’s front edge at a time, use a small drawknife to cut the lip (right). For maximum comfort, the transition between the dished out portion of the seat and the bevels should be smooth and gradual. The same should be true of the transition between the bevels and the flat section around the circumference of the seat. Finish smoothing the lip with a spokeshave.
Carving the channel
Use a Yt-inch veiner to carve the channel that separates the seat’s scooped-out top surface from the flat section around its circumference (left). This is a decorative groove designed to sharpen the transition between the curved and flat portions of the seat.