One of the most exciting things about chairmaking is the seeing the transformation of a rough board into a bent chair leg. This morning I was preparing a pair of rocker legs for a student who is coming here in October for a class. Because the rocker is such a complex chair I do all of the steam bending and most of the rough milling of parts beforehand, so that the student will have time to work on the numerous hand shaping, mortising and assembly steps.
Below are three walnut boards from a log I had custom milled specifically for chair parts. The log was very straight and there was no discernible twist in the pattern of the bark as it moved up the tree — twist would indicate that the wood within might be twisted as well. The sawyer aligns the log so that he is cutting parallel to an imaginary line running from center to center. This results in boards with the vertical grain running parallel to the board. These boards are cut to 9/4 thickness which allows for efficient milling of various chair parts.
Every chair part has its own requirements for end grain orientation. These requirements generally have to do with optimizing the natural wood movement in each part relative to the part it is joined with. For rear legs I am looking for rift sawn end grain — 45° or less. As you can see from the photo below the center of this board is rift sawn. On the right is sapwood which will be discarded. On the left is generally flat sawn grain which is perfect for the rocker arms. I will also be able to get front legs from the flat sawn side. For turned parts, like the front legs, end grain orientation in the board is immaterial — simply rotate the part at assembly to the desired end grain orientation.
The photo at right shows how I rough milled the board. The rear legs, which will be steam bent, have the most demanding requirements and need to be free from defects, especially in the area to be bent. Since the grain on the lower part of this board flairs out dramatically toward the bark edge I decided to move about two feet up the board before starting the cut for the rear legs which need to have very straight vertical grain. The rear legs are about four feet long, rift sawn, and cut as parallel to the grain as possible. The bark edge, which is mostly sapwood, will be discarded. On the left side of the board, which is flat sawn, I have cut both arms and both front legs. The remaining pieces, top and bottom right, will be suitable for rungs or possibly front legs for another chair. When I saw the piece on the lower right I will make my cuts parallel to the grain rather than parallel to the edge of the board so that the vertical grain runs as straight as possible within the part. The only remaining parts, slats and runners, will be cut from a quarter sawn board.
Once the rear legs are rough milled I look at each leg to determine its orientation in the chair — top and bottom, front and back, and left side or right side. Then I mill the legs to the correct width, thickness and height using the band saw, jointer, and thickness planer.
The last step before steaming is to cut a taper on the top, front face of each leg. I use a dedicated taper jig on my table saw to make this cut. This is the only milling step I do on the table saw, but it can also be done freehand on the bandsaw and then cleaned up with a hand plane.
Now I’m ready to steam the rear legs. I use a simple plywood box that is 48” long and about 7” x 7” square. The rocker legs are a bit over 49” long so I made an extension that slips into one end of the steam box. I use two Veritas kettles that produce plenty of steam. Unfortunately these are no longer available. In the near future I will be experimenting with wall paper steamers to see if I can get similar results. After placing the legs in the box and turning on the kettles I wait until the interior temperature reaches 200° before I start timing. Walnut of this thickness requires two hours in the steamer. In order to maintain that temperature I always preheat the water before refilling the kettles.
And, here I have temporarily removed the legs from the bending forms prior to putting them in drying forms. The drying forms are identical to the bending forms except they are missing the bending strap and strap clamp. Although moving the legs to the drying form is not essential, this will expose the front of the leg making the drying a bit faster and more thorough. Next I put the legs, in their drying forms, into a small, insulated closet heated with a ceramic heater to dry. In about a week the legs will be ready to work.
There is still much work to be done — post-bend milling, slat mortising, hand shaping, and rung mortising — before the rear legs are ready for assembly. But in those first few hours, seeing a rough board transformed into a bent chair leg, never ceases to amaze and excite me.
Jeff Lefkowitz | September 18, 2012