Paragraph 72. In making up wide boards, such as table tops, drawing boards, or any other cabinet construction in which it is impractical to use one wide board, dowels are frequently used. The purpose of the dowels is to reinforce the glued joints. Dowels may be placed in the joint at any distance apart. In work subject to great strain the dowels are frequently placed within a few inches of each other. In other work they are placed farther apart. This must always be a matter of judgment. The size (diameter) of the dowel depends upon the thickness of the board to be joined. In 7/8" or 1" material, 1/4" or 3/8" dowels are commonly used, extending l 1/2" or 2" into the edge of each board. Dowels are usually covered with glue, thus when the edges of the board are glued together a very strong joint is made.
See Chapter II., Paragraphs 18 and 13. Saw short pieces of dowels just long enough to fill the depth of the holes in board A and extend enough to fill the holes in board B. Put some glue on the dowels and drive them into board A. Then to make sure that the dowels are not too long, measure the distance they extend and measure the depth of the holes in board B. Cover the dowels with glue, also glue the edges which are to join. Make sure that the face side of the two boards are turned in the same direction; drive the boards together. After the boards are driven together they should be clamped very tightly with a steel clamp. If you have no steel clamp, substitutes may be made by nailing some blocks at convenient distances apart on any rough piece of material and tightening with wedges. Dowel joints should be clamped twelve to twenty-four hours to give the glue a chance to harden.