Excerpted from Peter Galbert’s “Chairmaker’s Notebook.”
While the softness and flexibility of the green wood is obvious, you might wonder what the advantage is of split wood. Working from split wood can be a tough concept to grasp, even for the experienced furniture maker.
Trees don’t have any flat or square parts, and wood is not a homogeneous material that’s indifferent to the way it is cut. Trees are a bundle of fibers, and once the tools and techniques to split and shave these fibers come into play, hand-tool jobs that would be difficult or tedious with sawn planks become simple and fast.
One way to compare sawn wood to split wood is that a saw blade ignores the fibers and cuts across them. Splits follow the fibers, which yields strong parts that display amazing flexibility without a loss of strength.
But there is more to this story.
Whenever sawn wood is shaped, shaved or cut with hand tools, the direction of cut is of primary concern. A smooth surface can be created by cutting or shaving the fibers in the direction that they ascend from the sawn board. Cutting in the opposite direction, where the fibers descend into the board, will cause the cutter to grab the exposed end grain and lever out small chips. This “tear-out” leaves a rough, undesirable surface and takes more effort to cut.
On sawn boards, the direction can change from one area to another, especially if the tree didn’t grow straight. The showy grain patterns so prized in cabinetwork are the result of milling across the fibers, whereas split and shaved pieces will have uniform – perhaps even boring – figure.
But showy grain can force you to constantly change your cutting direction to avoid tear-out, which slows the process. Plus, when shaving round parts from sawn wood, you will usually have to change direction as you shave around the surface. On the lathe, changing direction is impossible.
But when parts are split and shaved to follow the fibers, the direction of cut is simplified. You always head from the thick area to the thin. On round parts, this allows you to work around the entire piece without changing direction.
This enables you to rely on the shape of the piece to dictate the tool’s cutting direction instead of constantly interpreting the surface for clues.
Split wood can be worked in either direction when shaved parallel to the fibers. Once the fibers are carved across, the direction of cut is always toward the thinner area.
This simplifies and speeds the shaping process. Trying to shave a sawn spindle that has fibers that are not parallel to the axis of the spindle requires a constant changing of the cutting direction, which renders the process impractical.