The Technique of FURNITURE MAKING

Secret (double lap) dovetails

These are used where open dovetails would be unsightly, but as one lap must show end grain the jointing method could be entirely hidden with secret mitre dovetails, which are not much more trouble to cut. The double lap dovetail does, however, have certain applications, and 155:1 shows two forms: (B) side lap and (C) top lap, according to the use. In working the joint the projecting lap piece is rebated/rabbeted out (A) to the depth of the secret lap (the laps are usually made square in section). The pin piece is then set out and cut in the normal manner, and the tail piece set out from the pin piece as in secret mitre dovetailing (155:3), using an awl point as shown. A variation of this joint is shown in 155:4 where the carcass top is

Dovetails need not necessarily follow the traditional pattern, and the writer has used other forms, of which 155:5 is an example. The dovetail is cut and trimmed and marked round for the socket in the end grain. Holding power is as good if not better than the usual form of dovetail, providing the width of the tail is not too great.

Rebated/rabbeted or mitre box corner dovetail joints

Small boxes, trays, etc. are often rebated/ rabbeted for a lid (157:1 A) and if through dovetailed in the normal way may show a small gap on one piece at the end of the rebate; the half pin is, therefore, laid out below the rebate, and the shoulder of the pin piece brought forward to close the gap. Figure 157:2 is an alternative form where the gap is sealed by the tail piece. If the top of the box or frame shows a mitred edge (157:3) the top pin is not cut through at X, and if the sides are rebated then the depth of the mitre should equal that of the rebate.

Canted dovetails (bevelled work)

If one piece is canted as in a drawer front, the dovetails must not be set out at right angles to the cant but equal either side of a line drawn parallel to the long edge, or weak grain will result and loosen the joint. If the front is upright and the side canted then the tails are set out in the usual way, but the shoulders are sawn parallel to the bevel of the long side edge and not at right angles. Whichever piece is canted must be cut full to allow for the bevelling, and the bevel clearly marked or part of the half pin may be lost if the allowance is insufficient. (See also Double bevel dovetail joints, below, and Canted fronts, pp. 249-50.)

Double bevel dovetail joints

These joints are sometimes used for bevel-sided hoppers, knife-boxes, etc., and although rarely used are worth describing for the sake or the principles involved in setting or laying out bevelled work. A full-size drawing is necessary from which the true length (A) and the true width (B) can be obtained (158), also the edge bevel in the thickness of each piece shown by the arrowed line (c). All the bevels are marked and worked holding the bevel at right angles to the edges of the sloping ends and not parallel with the sides. A marking-gauge cannot be used for setting out the dovetails, and depths etc. must be marked with pencil and adjustable bevel, while the dovetails are cut to slope equally either side of lines drawn parallel with the sides (see Canted dovetails above), but the pins are, of course, parallel. In cutting the dovetails above the piece should be canted to bring the cuts vertical, as in 158D but marking
the pins by drawing the saw point through the tail kerfs is difficult owing to the slope, and therefore it is better to chisel out the dovetails and mark around them on the pin piece with an awl.