In sawing dimension timber, or “bill stuff,” good judgment is necessary to cut a log so that the greatest amount of marketable lumber can be made from it. This is done by cutting various sizes from a log, if it will not cut all of one size without too much waste.
(D.) In cutting woods which have prominent medullary rays or silver grain, the log is sawed by one of the methods shown in Fig. 16, the object being to bring the rays as nearly parallel to the surface of the board as possible, thus giving the broad silver, or quarter, grain which is so highly prized.
The best results are obtained from sections a, b; this method also gives the most waste. In plain sawed lumber, the boards from the middle of the log will have the quarter grain; these are usually culled and sold as quarter-sawed.
Neither of these methods results in economy of time or material, as about 25 per cent of each is used in excess of that required in plain sawing; hence, quarter-sawed lumber is more expensive than the plain, or bastard, sawed.
(E.) Quarter-sawed lumber (Fig. 16) is preferred not only on account of its handsomer grain, but because it holds its shape better than lumber sawed in any other way, as the annual layers are approximately square with the surface of the board. As the board shrinks in the direction parallel with the annual layers, and very little from the center to the outside of the tree, it is obvious that there is much less shrinking and warping in quarter-sawed lumber than in that which is sawed plain.
The best grades of flooring are quarter-sawed, and stand usage without the surface splintering much better than does the common plain sawed material. Quarter-sawed lumber is known also as “rift-sawed,” “vertical grain,” and “comb grained.”
10. The grading of lumber.—Custom varies somewhat in different localities as to the grading of lumber, but there are generally four grades, which are often subgraded into qualities suitable for various uses.
“Number 1” lumber should be practically perfect, though in large dimensions, small and unimportant blemishes may be allowed. These blemishes in a board are usually restricted to not more than one inch of sap, a small sound knot, or small discoloration, and but one blemish to a board is allowed.
“Number 2” lumber is generally allowed two sound knots, an inch of sap, and one other blemish.
“Common boards” are allowed three or four sound knots, but two thirds of one side must be clear stock.