ANATOMY OF A FRAME CHAIR

Подпись: Greet rail (page 32) Anchors tope of elate. Shaped to fit the back; upper edge can be curved Подпись:Подпись:Подпись:Подпись:ANATOMY OF A FRAME CHAIR

Pear leg (page 23)

Cut from a single length of solid stock. Shaped to suit the shape of users back and balance the chair visually, top ends may be chamfered for decorative effect. Section of rear leg above seat sometimes referred to as a stile

Side seat rail (page 33)

Supports the seat. Angled inward at the back; joined to front and rear seat rails by angled tenons. Bottom edge may have a bead for decoration

Front seat rail (page 36)

Supports the seat. Joined to the front legs by blind mortise-and-tenons; bot­tom edge may have a bead for decoration

ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIR

ANATOMY OF A FRAME CHAIRShop-made templates for frame chairs are like wooden blueprints drawn to scale, providing the exact dimensions of all the frame pieces as well as the positions of their mortises and tenons. Four main templates are typically required for a chair: one for the legs and rails, shown below—called the seat template—one for the rear legs (page 28), and two for the back rails (page 32). After the tem­plates are drawn, they are cut to shape on the band saw. The leg template shown at left will be used to shape the rear legs. Finished templates can be set aside and kept for future projects.

MAKING THE SEAT TEMPLATE

1 Outlining the legs and rails

ANATOMY OF A FRAME CHAIRMark out the seat template on a piece of plywood or hardboard. Start by drawing a rectangle to frame the seat, making its length equal to the width of the chair at the front—typically 18 inches. The rectan­gle’s width is equal to the chair’s depth, which should be slightly less than the chair width; in this case, the chair depth is 171^ inches. As shown at right, a frame chair seat is usually trapezoidal; make the back narrower than its front; in this example, 15 inches. In the front corners of the rectangle, draw in the two front legs, 1 Ya inches square. Then draw in the rear legs, making them wide enough to accommodate the tenons in the back and side rails; stock that is 1 inch thick by 2 inches wide should be sufficient. Next, connect the legs with reveal lines offset Vi inch from the outside edges of the legs. The lines represent the outside faces of the rails. The offset makes the chair more visually appealing than if the parts were flush. Draw in the inside faces of the rails so the pieces will be 1 inch thick.

2 Outlining the tenons

Due to the trapezoidal form of the chair seat, the tenons joining the side rails to the legs must be angled. Start by drawing in the tenons between the side rails and the rear legs. Mark the center of the contact area between one of the side rails and rear leg. Then, assuming ^-inch – thick tenons, mark the tenon cheeks, locating each one inch from your cen­ter mark. As shown at right, make the tenon cheeks parallel to the faces of the leg; this will allow you to rout straight mortises in the legs. Make the tenon % inch long. Repeat to draw in the angled tenon at the end of the other side rail. Mark the angled tenons joining the side rails to the front legs so they will be the mirror-image of those at the back end. If, for example, a tenon cheek is V* inch from the outside face of the rail at its back end, it should be % inch from the inside face of the rail at the front. Next, draw in standard blind tenons joining the front and back rails to the legs. The tenons in the back rail should be centered in the rail, whereas those in the front rail must be offset toward the rail’s outside face to avoid contacting the angled tenons in the side rails. Make sure that there is at least % of space between the tenons in the front legs.

ANATOMY OF A FRAME CHAIRFRAME CHAIR CUTTING LIST

Подпись: PART QUANTITY DIMENSIONS Front legs 2 IK' X IK* x 16# Rear legs 2 Front seat rail 1 1-х 2-х 16’ Back seat rail 1 l‘x2'x 14# Side rails 2 ічг'х is# Crest rails 1 1# X 3# X 14# Back rail 1 1# x 2’ x 14# Slats 4 # x 1# x 18# Making a cutting list

Once you have completed the seat template, you can begin compiling your cutting list for the chair (left). As shown, the cutting list should list the individual chair parts, how many of each is needed, and the dimensions of each part. Since the template is drawn to scale, you can take the measurements of the rails directly from it. The crest and back rails (page 24) will be the same length as the back seat rail and a little thicker. The crest rail is also wider than the other rails. You will not be able to determine the precise size of the slats and the length of the legs until the leg templates are done (page 28). Refer to page 16 for information on using a cutting list to determine how much lumber you need to buy.

MAKING THE TEMPLATE FOR THE REAR LEGS

ANATOMY OF A FRAME CHAIR

1

Marking the angle of the back rest

Cut a piece of plywood or hardboard to the length of the rear legs—in this case, about 42 inches. Start by marking the locations of the seat and side rails on one edge of the template. The top of the seat should typically be about 17& inches from the bottom of the leg. Make the seat 1 inch thick and mark the 2-inch-wide rail directly below it. These marks define a flat section along the leg where the rails and seat will be joined to the leg. Extend the length of the flat section by % inch above and below it. This will help you avoid curving the flat section—and creating imprecise joinery—when you later sand the leg (page 31). Then use a protractor and a pencil to draw a line for the angle of the back rest above the flat section (lefth a 10° angle will yield a chair back that most people find comfortable, but any angle between 0° and 20° is acceptable. Extend the line with a carpenter’s square to the top of the template (as represented by the dotted line in the illustration).

ANATOMY OF A FRAME CHAIR

.

ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIR

Completing the rear-leg template

Complete the top half of the template by drawing a curve roughly parallel to the one you made in step 2. To define the beginning and end of the curve, mark a point directly opposite the rail mark 2 inches from the front edge of the template (mark A in the illustration above). Since the leg tapers toward the top, mark a point at the top that is only 1 inch from the first curve (mark B). Join the two marks using the same method shown in step 2. For the bottom of the leg, start with the curve at the back. Mark a point at the bottom (mark C) that is 1 inch closer

to the front edge of the template than mark B; this ensures that the back of the leg at the bottom will not extend beyond the top and trip up someone passing the chair from behind. Join points A and C. Finish the template by drawing the curve for the front of the leg at the bottom. For balance, esthetics, and strength, mark a point at the bottom (mark D) so the leg’s width at the floor will be midway between its width at the rail and the top, or 1V£ inches. Use a pencil and the springy wood strip to draw the curve (above).

A blank for one of the front legs of a frame chair is trued on a jointer. Push blocks are used to safeguard the opera­tor’s hands from the cutterhead knives. The stock for chair legs should be free of defects like knots, checks, and splits.

 

ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIR

MAKING FRONT LEG BLANKS

Gluing up the leg blanks

Подпись: /// r .'. *-v' If the front legs of your chair will be thick­er than the stock you have on hand, you can make leg blanks by face-gluing boards together. Cut the stock so the blanks will be slightly larger than the final size of the legs. In this case, the legs will be 1% inches square; their length, from the floor to the bottom of the seat, is typically 17^ inch­es. Glue up both blanks in a single setup. Spread glue on the mating surfaces of the boards, then use as many bar clamps as necessary to support the stock at 4-inch intervals, alternating the clamps between the top and bottom of the stock. Tighten the clamps (right) until there are no gaps between the boards and a thin bead of glue squeezes out of the joints. After the adhe­sive has cured, joint an edge and face of each blank, plane or rip them to their final width and thickness, and crosscut them to length.

ANATOMY OF A FRAME CHAIR ANATOMY OF A FRAME CHAIR

ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIRMAKING THE REAR LEGS

ANATOMY OF A FRAME CHAIR

MAKING THE BACK-RAIL AND CREST-RAIL TEMPLATES

 

Trammel point

 

Centerline

 

Crest rail tenon

 

Designing the templates

Since the back and crest rails of the frame chair share the same curvature, make templates for both pieces on a single piece of plywood or hardboard clamped to a work surface. Start with the back-rail template, drawing a rectangle as long as the gap between the rear legs and as wide as the rail stock thickness— about Г/ to 2 inches. Then mark a line down the center of the rectangle, extending it across the template and your work sur­face. Mark the thickness of the back rail on the centerline, in this case 1 inch from the top of the rectangle. Next, use tram­mel points to draw an arc on the template that intersects your rail thickness mark and the bottom corners of the rectangle. Draw a second arc parallel to the first, outlining the back rail (above). You will use this outline to cut both the back and crest rails to thickness (page 36). Then draw a third arc outlining the top of the crest rail (right). Complete the templates by drawing in the sides and bottom edge of the crest rail outline, and the tenons for both rails. (These elements are represented by dotted lines in the illustrations.) Cut out the templates and trace their outlines on your rail blanks. Trace the back rail outline on the top edges of both the back and crest rail blanks. Trace the crest rail outline on the face of your crest rail blank. Finally, saw blind tenons at the ends of both rails (page 36), then cut the rails on the band saw (page 33).

 

ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIR

ANATOMY OF A FRAME CHAIR

CUTTING THE CREST RAIL

 

ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIR

Подпись: Greet rail __ top outlineПодпись:1 Cutting the top edge of the rail

ANATOMY OF A FRAME CHAIR
ANATOMY OF A FRAME CHAIRANATOMY OF A FRAME CHAIR

Подпись: Sawing the crest rail to thickness Turn the rail blank so the marked outline on its top edge is facing up. Cut along both marked lines (above). This time, complete the cut, letting the waste fall away. (This same cut is used to saw the back rail to thickness.) Подпись: Severing the bridge Rotate the crest rail blank so the first face you cut is facing up. With the saw turned off, feed the blade into the kerf. Then turn on the saw and cut through the bridge to release the waste piece (above).

Set the crest rail blank face-up on the band saw table, aligning the blade just to the waste side of the cutting line for the top of the rail. Feed the stock into the blade, turn off the saw about halfway through the cut, and remove the work – piece. Then cut along the same line from the opposite end. To avoid detaching the waste piece from the blank and losing the marked outline on the top edge of the rail, stop the cut about / inch from the first kerf, leaving a short bridge between the two cuts (left).

Подпись: баск rail markANATOMY OF A FRAME CHAIRПодпись: MAKING THE SLATS
1 Determining the curve of the slats

Cut a blank wide enough to yield the number of slats you need for the chair. The thickness of the blank will determine the width of the slats, so make it 1 to 2 inches thick. Plan on producing an even number of slats so there will not be a single slat in the middle of the back rest exert­ing pressure on the chair user’s spine. Use the rear-leg template (page 29) to mark the curve of the slats. Mark the locations of the crest and back rails on the template, and add marks A inch beyond the first two to represent the ends of the slats that will fit into mortises in the rails. Next, place the template on the blank so the top ends are flush and mark the curve of the template on the blank with a pencil (left). Then cut along your marked line on the band saw and smooth the cut edge (step 4).

ANATOMY OF A FRAME CHAIR

ANATOMY OF A FRAME CHAIR

ANATOMY OF A FRAME CHAIRПодпись:

ANATOMY OF A FRAME CHAIR

4 Smoothing the slats

Sand the slats by hand or with a spin­dle sander (right), using progressively fin – er-grit sandpaper sleeves until the slats are smooth. With your right hand, feed the slats against the direction of the sanding drum’s rotation while applying pressure with your left hand.

5

Shaping the slats

Once all the slats are smooth, round their edges using a Me-inch piloted round – over bit mounted in a router table. To pro­vide a bearing surface for the slats, install the same fence and bit guard you used to shape the rear legs (page 31). Set the height and depth of cut using a piece of stock the same thickness as your slats. Then round the edges of each slat, feed­ing them into the bit with your right hand while applying pressure against the fence with your left (left). Keep your hands well clear of the bit throughout the operation.