The dovetail (Figure 2.24) is the strongest joint for joining pieces of wood together at right-angles in their thickness (side-grain to end-grain) and is widely used at corners for box, drawer and carcase construction. It consists of interlocking tails and pins that resist tension along the tail member but not along the pin member. In drawers, the joint is therefore oriented with the pins in the front and back of the drawer and the tails in the sides while in carcases the tails should be in the top to prevent the sides from moving outwards. The joint relies on the wedging action of pins and tails to hold it together in tension and on glue between side-grain to side-grain mating faces of tails and pins to hold it together. Therefore, the factors that affect both the strength and appearance of the joint are the number and size of the tails and pins and their slope. Provided that an adequate amount of wood remains across the narrow part of the tail, increasing the number of tails will increase the strength of the joint by providing an increased side-grain to side-grain gluing area. It is common to make the tails at their widest part about twice that of the pins but for the strongest work they can be equal. The slope or rake of the tails is a compromise, if it is too small the wedging-locking action will be lost but if too
Figure 2.24 Examples of angle joints: dovetail joints: (a) through dovetail; (b) lapped dovetail; (c) double lapped dovetail; (d) secret mitred dovetail. Joints used in carcases: (e) cross rails dovetailed into solid side; (f) cross rails dovetailed into framed side; (g) top dovetailed to side; (h) top dowelled to side; (i) top rebated; (j) housing; (k) tapered dovetail housing
great then a fragile component of end-grain will be introduced at the splayed tips of the tails that will also impair the side-grain integrity of the gluing surfaces. A slope of 1:5 or 1:6 for dovetails in carcase work, where appearance is of little consequence, is recommended whilst for show work such as drawer sides a slope of 1:7, and for very fine decorative dovetailing a slope of 1:8, has been suggested (Joyce, 1970).
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