This section is from the book "An Elementary Outline Of Mechanical Processes", by G. W. Danforth. Also available from Amazon: An elementary outline of mechanical processes.
Wood for general uses is handled commercially in the form of lumber or timbers. Trees are felled, and that part of the lower trunk free of large limbs is sawed into logs usually a few inches longer than an even number of feet. These logs are hauled to the sawmill and sawed into widths and thicknesses as required.
The log end in Fig. 2 is numbered to show the consecutive cuts in the usual method of sawing. Most of these are tangential cuts, i. e., more nearly perpendicular than parallel to the radius of the log end. Pieces 20 and 21 are known as quarter-sawed pieces, as their width is cut along the radius of the log end. Tangential cuts are cheaper because of less handling on the saw carriage and less waste of the log material, but lumber from these cuts warps more, is less durable, and does not show the fineness of grain when compared with quarter-sawed lumber. The upper half of Fig. 3 shows a method of getting more quarter-sawed cuts from a log than are obtained in Fig. 2 without greatly increasing the cost of cutting. The log is quartered and each quarter is sawed into pieces as consecutively numbered, quadrant A giving two quarter-sawed pieces, 1 and 2, and two pieces, 3 and 9, which are nearly quarter sawed. Quadrant B shows another method of sawing, giving pieces 3 and 11, quarter sawed, and but one piece, No. 10, corresponding to pieces Nos. 3 and 9 of quadrant A. True quarter sawing is shown in quadrant D, and approximate quarter sawing, with less waste, is shown in quadrant C, of Fig. 3.