The Technique of FURNITURE MAKING
Carcass dovetails
Where a side rail is grooved or tenoned into a leg or post as in a framed-up carcass, the shoulders of the two dovetails must be offset; moreover in tenoned work the tenon and haunches must be set down by an amount at least equal to the depth of the larger dovetail. Figure 159:1 shows a typical assembly with front rail dovetailed into post and side rail. The side rail and post are assembled first and flushed off,
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159 Carcass dovetails the thickness of the front rail gauged in the post and pencilled in on the side rail if the gauge cannot reach, and the larger dovetail set out, using the same gauging for the smaller dovetail if the shoulders line through, or resetting it if it projects (159:2). Subsequent marking is as for other forms of lap dovetail. Where the carcass panel is either solid wood or plywood, etc. a front rail (159:3B) and intermediate rails (A) are lap dovetailed in, and the latter either dovetailed as (B) or with a single large tail (A) which can be prevented from lifting by a countersunk screw. Continuous tops should be as 154:5 with a small dovetail at front and back to prevent the cheeks from curling. A suitable rake for carcass dovetails is about 1 in 5, and the spacing can be fairly coarse with the width of the tails about two and a half times that of the pins
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161 Solid top of a Scots pine linen chest with a dry dovetailed joint |
(2.5:1); but there are no fixed rules, although the narrower the tails the greater the holding power.
Slot (slip) dovetails
These are cut in the width rather than the thickness and are used in stretcher frames, plinths, cornices, etc. They can be either bare face, i. e. tapered on one side only (160: lA), double tapered (160:IB) or stopped (160:2), with the last more laborious as they cannot be sawn through but must be chiselled out, and are therefore only used where the actual joints must be hidden on one face. In practice, bareface dovetails are sufficient for normal work, and they can be further strengthened with a glue block in the bareface corner.
Another variation on the slip dovetail is when stiff, usually hardwood, members are assembled unglued into dovetail slots under a solid wood table top or lid of a chest. The dry dovetailed joint allows the solid top to move freely in changing humidity at the same time as remaining flat on its top surface. Figure 161 shows such a hardwood member, one of a pair, being fitted into a wide board of Scots pine which will form the lid of a linen chest. The lid will be locked at its centre by a screw which will then allow equal movement from either edge.
