Friday, August 1, 2008

How-To: Four Board Bench - American classic

The four board bench is an American classic. It has been made throughout history wherever people have gathered. This bench was developed using shaker originals as a model for the proportions, leg shape and stretcher profile. The journey in the bench is a combination of dadoes and wedged through tenons, used by a shaker community in Kentucy during the first half of the 19th centure. Many woods are appropriate for this bench, we chose this walnut for its sap wood sides and edge glued the stock so the sap wood strip ran down the approximated middle of the seat.

1. If you are making a panel to match the width in the cutting list for the seat (A) and legs (B), then choose your stock to make a strong relationship between the members. We organized the heart wood and sap wood, book matching could also make a strong relationship. If you are using 8-1/4" wide stock for the seat and legs, then proceed to step three.

2. If you are edge gluing the seat, apply glue to each interior face and fix them with alternating clamps separated by about 18". Once the glue has cured, run the panels through a planer or level with hand plane.

3. Cut the seat, legs and strecher (C) to the dimensions given in the cutting list. The legs are positioned 5 1/4" from the ends of the stretcher and are secured with lapped dado joints, as located in the drawing on page 35. Cut the 3/4" x 1"deep dadoes into the stretcher using a right angle miter fence on the table saw. The dadoes in the stretcher join with corresponding 3/4" x 2 7/8"deep dadoes in the center of each leg, mark and cut these dadoes. Each leg secures the seat with two tenons that are 5/8" x 3/4" x 11/4" wide. Layout the tenons on each of the legs 7/8" from each leg side and clear the waste using a right angled miter fence on the table saw.

4. Transfer the profiles from the pattern inserts to the seat, stretcher and legs. Cut the profiles just shy of the lines with a band saw. The seat is secured by each leg with a 1/4" x 3/4" dado cut across the width of the underside of the seat 7 1/4" from each end. Check to see that they match the dadoes in the stretcher and cut the seat dadoes with a right angle miter fence on the table saw.

5. The leg tenons are secured in their mortises with wedges pressed into their slots. See step seven for information about the wedges. Cut the wedged shaped slots centered along the length of the leg tenons with a back saw. Layout the the 3/4" x 11/4" wide mortises in the seat by marking up from the dado edges on the seat sides with a tri- square. Mark the mortises in the other direction by using the leg as a guide.

6. Score the perimeter of each mortise on the seat top with a utility knife and drill out the waste. Cut the remaining waste from each mortise with a paring chisel and mallet. Smooth the bandsawn curves with a block plane, spoke shave, rasp or a sharp chisel used as a scraper.

7. Cut the wedges (D) to the dimensions given in the cutting list. Shape a shallow angle into each wedge. Its width should be slightly larger than the width of the leg tenon. When the wedges are fully engaged with the notches in the leg tenons, they should press the tenons into compression between the walls of the seat mortises.

8. Dry fit the assembly and check to see that all joints are true. Disassemble and apply glue to the joints. Reassemble the seat, legs and stretcher and tap the wedges into place. Once the glue has cured, cut the wedges flush with the bench top. Sand the bench through 220-grit sand paper and finish with oil and wax.

Cutting ListQty
ASeat3/4" x 8 1/4" x 40"1
BStretcher3/4" x 3" x 34"1
CLegs3/4" x 8 1/4" x 15 3/8"2
DWedges1/4" x 1 5/16" x 1"4

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