(B.) In surveying joists or scantling, it is customary to obtain the fraction of a foot, board measure, for each lineal foot. Thus, a piece of 2 × 4 (inches understood) has two thirds of a foot for each foot in length; a 2 × 6 has one foot, and a piece of 2 × 8 has one and one third feet of lumber for each foot in length of lumber measured. If a joist is 2 × 12, doubling its length gives the number of square feet, board measure, that the joist contains.
(C.) In measuring a common board, the widest parallel piece which can be cut from it is the width of the board being measured; therefore the board should be surveyed at the narrowest place. In measuring more expensive lumber, it is customary to average the width of the board.
(D.) In estimating all kinds of lumber in common use, the lumber scale shown in Fig. 17 is used. It is made of thin, cleft hickory, about three feet long, with one end large enough for a suitable handle; on the other end is a metal head, which is held against the edge of the board while the scale is being read.
The length of the board is marked near the handle, and at the end of the socket of the metal head, as at a.
In using this scale, the hooked end, or head, is held against the edge of the board, as at b; the eye follows along the same line of figures upon which the length of the board is found, reading those figures nearest the width of the board. Thus, a scale laid upon a board 16’ long would, without further measuring or calculating, show that the board contains 17’ board measure. If the board were 12’ long, it would contain 13’; and if 14’ long, by reading the middle line of figures, the board would be seen to contain 15’.
In using this scale, it is customary to read to the nearest figure, and when there is no difference, to alternate between the lower and the higher figures upon different boards. Thus, a board 12’ long and 8¾” or 9¼” wide would be read as having 9’ board measure in it. Two boards 8½” wide, of the same length as the above, would be measured as having 8’ and 9’, respectively, in their surfaces. In short, the fractions of a foot are not considered in surveying the lumber in common use.
Fig. 17.—Lumber Scale.
13. Qualities of wood.—(A.) Certain kinds of wood are adapted for some purposes better than are others; the wood-worker, therefore, should be familiar with the qualities which conditions demand, and the kinds of woods which have these qualities.
Lumber for framing should be strong and durable; it should be cut from trees which grow to a size that will allow large dimensions to be cut from them.