Grading of Lumber

Abstract The grading of lumber starts with the growth of the tree. As the tree develops from a seedling branches are formed, some of which become large and remain in the tree as long as it lives, others die or are broken off and the stub eventually becomes covered by the wood of the tree. During the lifetime of the tree it may go through periods of drought, which affect the wood produced during that period; it may be affected by wind storms producing shakes, which are longitndinal separations of the wood fibers, and it may be attacked by fire. Pitch pockets and other variations of growth may be formed. As a result, the lumber produced from a log will vary from that which is clear and without defect to that having many defects. In addition, certain accidents of manufacture, machine damage, overstressed wood due to rough handling, cracks, broken pieces, etc., also appear in the lumber. All of these things affect the grade of lumber sawed from the tree.