No. 25. A dado or grooved joint is made by cutting in one member a groove into which the end or edge of the other member fits. Properly speaking a groove runs with the grain, a dado across it, so that the bottom of a drawer is inserted in a groove while the back of the drawer is inserted in a dado. Where the whole of the end of one member is let into the other, such a dado is also called a housed dado. Treads of stairs are housed into string boards.
Fig. 266-25 Dado
To lay out a dado joint: After carefully dressing up both pieces to be joined, locate accurately with a knife point, on the member to be dadoed, called X, one side of the dado, and square across the piece with a try-square and knife. Then locate the other side of the dado by placing, if possible, the proper part of the other member, called Y, close to the line drawn. If this method of superposition is not possible, locate by measurement. Mark, with a knife point, on X, the thickness thus obtained. Square both these lines as far across the edges of X as Y is to be inserted. Gage to the required depth on both edges with the marking-gage.
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 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.
Fig. 266-26 Dado and rabbet