Dovetailing
Also called: cutting dovetails
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Dovetailing joins two boards, usually at a corner, by cutting a row of wedge-shaped projections on the end of one board and matching sockets, or hollows, on the other, so the two boards interlock when pushed together. Tredgold (1871) defined it as "the joining two boards by indenting them together, the sections of the projection and hollows being in the form of a dovetail." Because each projection, usually called a pin, is wider at its tip than at its root, the joint grips against being pulled straight apart even before any glue goes on.
Kinds of dovetail joint
Not every dovetail joint looks the same. The plainest form, through dovetailing, is cut so the pins and sockets pass right through both boards and show on both faces at the corner; Fairham (1920) calls it one of the simplest forms of the joint. Where the joint has to close a corner but end grain must not show on the front face, as on the front of a drawer, the pins are cut only part way through the front board instead of all the way through it. Fairham (1920) explains that lap dovetailing exists for exactly this reason, since "it is not permissible to allow the end grain of the timber to show at the front of a drawer." Hasluck (1897) describes the same arrangement worked out in a real drawer: the sides and back joined with dovetails cut right through both boards, but the front cut only part way through its thickness so the joint does not show from outside. Tredgold (1871) draws a further distinction by where the corner sits: at a re-entrant angle, the inside of an L shape, he judged common, through dovetailing best, calling it strong, cheap, and hidden except where the pins show on the outer face; at a salient angle, the outside corner of an L, that same showing of end grain is unwanted, so a concealed form is used instead. Tredgold also describes lap dovetailing as hiding the dovetails themselves while still showing, on the return side, the thickness of the lap, "which appears like the edge of a thin board." A third named form, mitre or secret dovetailing, hides the joint completely on both faces; Ellis (1908) records it being used on the salient angles of plinths, cornices and desks in high class work, and notes that cutting this form calls for the pins to be cut first. Ellis also states that there are three types of dovetailing in general, differing mainly in the size and spacing of their pins, variations which are sometimes used to name the type.
Cutting the joint by hand
Before any sawing starts, the ends of the boards are squared up and a line is gauged across each, marking the exact thickness the pins and sockets will be cut to; Fairham (1920) treats this squaring and gauging as the first step in dovetailing a drawer or box. Bird (2004) recommends marking the cut lines by scoring them into the wood with a knife or gauge rather than drawing them in pencil, since an incised line is easier to saw and chisel to accurately. When the pins are sawn out, the saw itself removes a thin slice of wood, the kerf, so Hasluck (1897) points out that the waste must be cut away exactly on the marked line, or the saw's own kerf will leave the pins loose in their sockets instead of a tight fit. A dovetail saw, thin bladed and finely toothed, is the tool traditionally kept for this work; Disston (1923) lists a further pattern of saw made specifically for it. Holding the work is part of the difficulty: Landis (1987) notes that a narrow-jawed vice with its screw set in the middle leaves little room to hold a board upright while it is sawn, which dovetailing usually requires. Frid (1979) warns that a common mistake for someone new to the joint is to cut the pins deliberately oversize, meaning to fit them later by paring down with a chisel, rather than sawing accurately to the line in the first place. Rogowski (2002) is more encouraging: in his view, anyone who can already saw to a line and handle a chisel can learn to cut a through dovetail by hand with practice.
Cutting the joint by machine
A dedicated dovetailing machine, guided by a template, can cut a full set of matching pins and sockets faster than they can be sawn by hand, and Joyce (1987) notes that such machines can even dovetail a curved drawer front, which hand work would struggle with. For a workshop that only dovetails occasionally, Joyce describes accessories and attachments, including some offering several different pitches, or spacings, of pin, as an alternative to owning a full machine. A router guided by a template achieves a similar result on a smaller scale; Hylton (2005) notes that a half-blind dovetail jig, which produces the lap-style joint that hides the joint from the front, is the one most often reached for when dovetailing a drawer. Duginske (1999) points out one practical difference this makes: because a template-guided machine or jig cuts every joint to the same fixed pattern, the boards need not be individually marked and matched to each other the way they must when dovetails are cut by hand, where each pin is fitted to its own particular socket. For very large numbers of joints, Frid (1979) describes cutting dovetails on a circular saw instead.
Practical notes
Hodgson (1902), writing at the start of the twentieth century, thought hand dovetailing was already becoming rare among general carpenters, observing that "the art of dovetailing is almost obsolete among carpenters," with the work passing to cabinetmakers and to specialist workers in factories. He nonetheless urged every young workman to learn to cut a good dovetail, insisting it was not a difficult operation once learned. A newly cut dovetail joint also needs a little time before it meets veneer: Jones (1920) advises leaving several days between dovetailing a carcase and veneering over it, because the end grain exposed in the joint shrinks less than the surrounding wood as it dries, and if veneered too soon the outline of the dovetails will eventually show through the veneer as that shrinkage happens. Because the joint calls for accurate sawing to a fine line, Bird (2004) suggests reserving a workshop's sharpest chisels for cutting dovetails and fine joinery generally, rather than everyday use.