Segmented Woodturning is woodturning where the initial work piece is composed of numerous glued-together wedge shaped segments.
In traditional wood turning, the work piece is a single piece of wood. The size, grain orientation and colors of the wood, will frame how it can be turned into an object like a bowl, platter, or vase. With segmented woodturning, the size, shape and patterns are limited only by imagination, skill and patience.
In addition to design skills, segmented woodturning demands precision woodworking skills as well as turning skills. Design and construction requires angled miter joints cut to tolerances of as little as a tenth of one degree or less.
There are essentially four different techniques for constructing a project; Closed segmented construction, Stave construction, Open segmented construction and Transitional construction.
Closed Segmented Woodturning construction is the most common. Rings (layers) are constructed of individual wood segments and the rings are glued in a cylindrical stack. Each ring commonly contains 8 - 24 pieces, the more pieces in a ring, the more challenging. Individual pieces making up a ring themselves are often assembled from smaller pieces of contrasting or complementary colors to achieve striking patterns in the finished piece. The wood grain in a ring-constructed turning runs horizontally, with joints in the rings overlapping the previous rings segments for stability.
Stave Segmented Woodturning constructions are assembled like barrels/cylinders constructed from multiple long, vertically-oriented pieces. The grain in a stave constructed turning runs vertically, from top to bottom. Quite often there are normal segmented rings added above or below the staved ring for design purposes. In these situations, the ring constructed grain must run vertically as in the stave ring.
Open Segmented Woodturning construction is similar to closed segmented construction but small gaps are left between the segments. Successive rings are offset so the segments interlock with the ring above and below. This type of segmentation seems very delicate and is somewhat transparent but it is generally quite strong.
Transitional constructions are turnings which combine ring construction or stave construction with solid, non-segmented wood such as a burl. However, wood expands and contracts in the direction perpendicular to its grain as a function of its moisture content, itself a function of ambient humidity. In this case, during design and assembly, theturner has to be mindful of the impact on long term structural integrity of assembling the constituent pieces into incompatible, non-parallel grain directions.