Hardwood Lumber Grades in the United States
In the United States, standards for grading hardwood are set by the National Hardwood Lumber Assn. The standards are voluminous, replete with exceptions, special rules for certain species, and many details. Here we will only try to illustrate the principles behind the grading, with a few indications of how the home woodworker can use them. For details, contact the association.
Unlike softwood, most hardwood is used in applications where appearance is crucial, such as furniture. Hardwood being a natural product, no two boards are alike, and almost all contain defects like knots that would be unacceptable in a piece of fine furniture. In most cases, however, only one side of the board will show. The grading of hardwood reflects that; it is based on the number and size of the “clear face cuttings”–rectangular pieces free of defects on the graded side–that could be cut from the board being graded. The other side of a clear face cutting may contain defects, as long as they don't affect the strength of the cutting. The fewer and bigger the clear face cuttings, the higher the board's grade. Grading a board doesn't involve actually sawing the clear face cuttings from it; they are purely conceptual.
The three top grades are
The remaining grades–2A, 2B, 3A and 3B–rarely reach the retail market; manufacturers make flooring, pallets and similar products from them.
The best way of grasping the puzzle-like nature of grading hardwood is to consider a real example. Here is one from the Wood Handbook, by the Forest Products Laboratory of the U. S. Department of Agriculture (Washington, 1974).
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