Converting a log into lumber requires certain compromises. Most logs are sawn in one of three basic ways. The simplest method squares the log and slices it into boards straight through from one side to the other. This technique, known as through-and-through sawing, results in stock cut tangentially to the annual growth rings. A second method, plainsawing, is similar, except that the log is rotated as it is cut, and the low-quality pith is set aside for items such as pallets. Plain-sawn lumber is also known as flatgrained lumber.

The third method. called quarter-sawing or edge-grain sawing, divides the log into four quarters and cuts every board more or less radially. Quarter sawn boards have their annual growth rings perpendicular to the face.

This orientation of the growth rings accounts for the dimensional stability of quarter sawn boards. Wood shrinks and expands roughly twice as much tangentially to the rings as its does radially. When quarter sawn boards swell or shrink they do so mostly in thickness, which is minimal, whereas a plain-sawn board changes across its width. A dining table made from plain-sawn pine boards, for example, can change as much as 1 inch in width a similar table made from quarter sawn boards would only swell or shrink by one-third as much.

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Quarter sawing also offers an esthetic advantage: It exposes the medullary rays that radiate from the heart of a log like the spokes of a wheel. In most species the rays are only one cell thick, but in a few species, such as oak, the ray ceils are thicker and appear as vivid streaks scattered along the grain. Sycamore, poplar and basswood are also ideal candidates for quarter sawing.

Quarter sawn lumber is not always cut perpendicular to the grain, and some through-and-through cut boards close to the center of a log will have quarter sawn grain. Therefore, no matter how they are actually cut, boards with growth rings at angles between 45′ and 90′ to the wide surface are classified quarter sawn, while boards with rings at 0o to 45o angles to the wide surface are termed plain-sawn. Boards with growth rings at a 30′ to 60′ angle are also called rift-sawn or bastard-sawn.

In actual practice, sawyers use a myriad of sawing patterns, depending on the type of machinery being used, the intended use of the lumber,log diameter and the type of tree. For example, in virtually all trees the pith or central core of the heartwood is less desirable than and not as strong as the rest of the heartwood. Plain-sawing “boxes out the heart” by cutting around it to eliminate it.

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