Shrinkage will take place in spite of all precautions, but this is not a serious matter, and does not affect the usefulness of the board.
All boards, it is conceded, should be "built up," rather than consist of one piece. The idea is that the warping of one piece is somewhat counteracted by that of the adjoining pieces in other directions.
[Fig. 206] shows three forms in common use. At a the ends are united to wide cleats by a tongue and groove joint.
In shrinking and expanding with weather changes, the board is free to slide along the joint, being glued only at the centre.
Fig. 206. The drawing board
At b two dovetail-shaped strips are inserted on the under side across the grain. This is more difficult cult to make on account of the shape of the groove, but it is otherwise satisfactory. At c two strong cleats are fastened across the under side by screws. This is the easiest and least satisfactory method, as the cleats are often in the way, making the board clumsy, and furthermore it does not allow for shrinkage, unless the screws are secured in grooves instead of in plain holes.
A good proportion for a small board is 24 × 18 inches. If the first method of construction is decided on, glue up four or five strips of well seasoned white pine, 7⁄8 inch thick, of the width desired, and four inches shorter than the final length of board. Place in clamps for twenty-four hours, and when dry dress down perfectly true to a thickness of 3⁄4 inch. Test for warp and wind, and square the ends.
Square up two pieces of stock 21⁄2 inches wide, with a length equal to width of board. For the tongue and groove joint, a set of tongue and grooving planes will be necessary. Two cutters for this purpose come with the modern universal plane, and if available this may be used. In either case, set the depth gauge at half an inch, and plow a groove on one edge of each strip 1⁄4 inch wide to the full depth, as shown at d. On both ends of the board, plane the tongue same size as groove at e. Coat the tongue at each end of board with glue for a distance of six or eight inches at the centre, fit the end strips in position, and place in clamps over night. When dry, give the surface a final truing up, and also the ends, as the clamps may have made a slight change.