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The lathe and slicer produce different grain patterns regardless of the wood species involved. A rotary grain pattern is produced on a lathe and consists of large, swirly patterns. These are not consistent in either size or pattern, and as noted earlier, are typical on many of the pre-finished panels seen in every lumber yard.
A large advantage of the slicer is the ability to produce selected grain pattern types with a predictable degree of consistency. The patterns produced are termed plain-sliced and quartered. Variations of these grain patterns called half-round and rift are produced on a face lathe. We will examine each of these in more detail, since they are the basis of the industry.
This is also called flat sliced, and plain sawn. If one imagines a log from the end with its concentric growth rings, the knife passes through the log on a plane tangential to these growth rings. The resulting grain pattern on the face of the leaf is a series of cathedrals, ellipses, and ovals. Though the variations are infinite, the basic grain pattern remains the same from log to log and species to species.
As the cant is prepared in the sawmill, the logs are quartered. This provides a surface which is a radius of the log. When sliced, the plane of the knife cut follows this radial direction. In theory each knife cut or slice would be a radius of the log. The result in this method is a straight line grain pattern.
This is a variation of the plain sliced pattern produced on a face lathe. The cant is mounted off center on the lathe and the plane of cut is in an arc tangential to the growth rings. It is used primarily to add width to narrow stocks by increasing the plane of cut, or to enhance a particularly wild grain pattern.
Oak has a particularly large medullary ray which runs in a radial pattern in the log. When quartered, these rays produce a large, splashy, "flake" patch. Since these flakes are not well liked at present, a technique was developed with a face lathe to manufacture straight-grained oak with a flake -- or rift. In this, the plane of cut runs on an arc approximately perpendicular to the growth rings.
The preceding grain patterns described are those produced through manufacturing techniques. There are other grain patterns that are produced by genetic "freaks" in each species. The most prominent is called cross-fire and is caused by interlocking and twisted grain fibers. When the knife cut passes through these in a straight plane, a series of highlights results. These can take the form of blocks, ripples, curls, and small patches, in almost infinite variety. They can show up superimposed on both a plain sliced or quartered grain pattern.
Another natural grain pattern is a burl. Classically this is produced from a large, knobbly growth on the bole of the tree. The grain pattern typically resembles a series of fish-eyes, laid side by side. These are also "freaks." Obviously the veneer leaf sizes are generally small and additionally are defective. While producing beautiful patterns burls are difficult to work.
The crotch pattern is another natural grain, and exotic in appearance. It is produced from the wood just below the first major branching of the tree trunk. The wood fibers here are so twisted and interlocked that the resulting grain patterns are infinite in variety. The classic crotch pattern much resembles a feather duster seen from the side. The mahogany crotch was much liked and often used by the 18th and 19th century cabinet makers.
Perhaps the most bizarre of the natural grain patterns is that produced by the stump. Here the grain pattern is always swirly and twisted, and is often accompanied by cross-fire and patches of burl. Again, the sheet sizes are normally small.
There are other lesser known and used patterns, but these are the most frequently seen. They form the basis of the many exciting patterns that can be produced from wood veneer.
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Last Updated: Friday, April 5, 1996
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