Fig. 9.—Testing Surface with Winding Laths.
The boards are then put on the top of one another as at [Fig. 1] and tested with a straight edge; they should appear true as shown at [Fig. 3]; if they show faulty as at [Fig. 4] the joints must be again fitted until the required degree of accuracy is obtained. Difficulties may be avoided by care in selecting timber suitable for jointing, and it must be remembered that timber shrinks circumferentially (the heart side becoming curved) as dotted lines in [Fig. 10]. If the timber be jointed with all the heart side one way as at [Fig. 10], the tendency will be for it to cast as shown by the dotted line. If the timber be alternated as at [Fig. 11], the tendency will be to cast wavy, whereas if quartered timber can be obtained it will stand practically straight as the tendency to shrink is in thickness only. The grain of quartered timber is shown in [Fig. 12].
Fig. 10.—Showing Heart side of Timber one way.
| Fig. 11.—Heart side of Timber shown alternated. | Fig. 12.—Grain of Quartered Timber. |
Fig. 13.—Boards showing uniformity of Grain.
Judgment should also be exercised to avoid jointing in which one piece of timber is wild and large in the grain, and the adjoining piece of a mild-grained nature. Jointed boards should always be glued up with the grain running in the same direction if possible; this we show at [Fig. 13], and nothing looks worse than a dressing chest end or similar piece of work in which the grain runs haphazard. When jointing thin timber (say, 1⁄4-in., 3⁄8-in., 1⁄2-in. and 5⁄8-in. boards) the best method is to use a shooting board ([Fig. 26]). It must be noted, however, that a shooting board and plane practically never give a true right angle, owing to wear and the grinding of the blade. Therefore, the boards should not all be laid with the "face mark" on the shooting board whilst the edges are shot, because any inequality would be multiplied by the number of pieces jointed. A better method is to alternate the boards, face side up, then face side down, whilst shooting the edges; this will prevent convexity or concavity on the face of the jointed board, because any slight error in the angle is neutralised (see [Fig. 8]).