To cut the joint: First make with the knife a triangular groove on the waste side of each line, as indicated in Fig. 91, p. 66, and starting in the grooves thus made, saw with the back-saw to the gaged lines on both edges. The waste may now be taken out either with a chisel or with a router, Fig. 122, p. 83. The second member, Y, should just fit into a dado thus made, but if the joint is too tight, the cheeks of the dado may be pared with a chisel. In delicate work it is often wise not to saw at all, but to use only the knife and chisel.
_No. 26. A dado and rabbet_, Fig. 266, is made by cutting a dado in one member, X, and a rabbet on the other, Y, in such a way that the projecting parts of both members will fit tight in the returns of the other member. It is used in boxes and gives plenty of surface for gluing.
_No. 27. A dado, tongue and rabbet_, Fig. 266, is a compound joint, made by cutting a rabbet on one member, Y, and then a dado in this rabbet, into which fits a tongue of the other member, X. It is used in machine-made drawers.
_No. 28. A dovetail dado or gain_, Fig. 266, is made by cutting one or both of the sides of the infitting member, Y, on an angle so that it has to be slid into place and cannot be pulled out sidewise. It is used in book-cases and similar work, in which the shelves are fixed.
To make this joint, first lay out the dovetail on the member to be inserted, called Y, thus: Across one end square a line (A B, No. 28), at the depth to which this member is to be dadoed in. Set the bevel-square at the proper angle for a dovetail, Fig. 250. Score this angle on the edges of the member, as at C D. Cut a groove with a knife on the waste side of A B. Saw to the depth A C, and chisel out the interior angle A C D.
Then lay out the other member, X, thus: mark with the knife the proper place for the flat side of Y, square this line across the face and on the edges as for a simple dado. Lay out the thickness of Y on the face of X by superposition or otherwise and square the face and edges, not with a knife but with a sharp pencil point. Gage the required depth on the edges. Now with the bevel-square as already set, lay out the angle A C D on the edges of X, and across the face at C score a line with knife and try-square. Cut out grooves in the waste for the saw as in a simple dado, and saw to the proper depth and at the proper angle. Chisel or rout out the waste and when complete, fit the pieces together.