Dovetailed joints are employed for uniting the ends of boards at right angles to each other, as in boxes, drawers, and numerous other works. The dovetails are made of several forms; thus, fig. 601 is a kind of factitious dovetail, in which the boards are first mitred, or their edges are planed at the angle of degrees, and slightly attached by glue or otherwise; a few cuts leaning alternately a few degrees upwards and downwards are then made with a back-saw upon the angles, pieces of veneer are afterwards glued and drawn into the notches. This method is principally employed in toys and very common works, which are then said to be mitred and keyed; the hold is much stronger than might be expected.
Fig. 692 represents the ordinary dovetail joint; p, fig. 693, the pins, and d, fig. 693, the dovetails of which the same is composed. In some cases the pins and dovetails are nearly alike in size, and this makes the strongest attachment; but in joinery and cabinet work, the dovetails are made on the front or more exposed part of the work, and the pins are cut of only one-fourth or less the size of the dovetails, in order that but little of the end wood may be seen. Usually the pins are the first made; as in making ordinary dovetails as well as tenons, the surfaces are left from the saw, this instrument must be well applied to produce the close joints met with in works of the best quality.
In setting out dovetailed works, the sides and ends of the box are first marked across on both sides with the gage or square at g g, which lines indicate both the inside measures of the box and the bottoms of the pins and dovetails; the portions beyond the lines are left a trifle longer than ultimately required. Very little care is taken in setting out the pins; indeed, their distances are usually marked with a pencil, without the rule or compasses, and the two external pins are always left nearly as strong again as the others.
One of the fronts, fig. 694, is fixed upright in the bench-screws, and the pins are sawn as shown at a a. These saw cuts are made exactly perpendicular, and terminate upon the gage lines; but horizontally they are sloped opposite ways, so that every pin is about as wide again on the inner as on the outer side of the front of the box. The wood between the dovetail pins is generally cut out with the bow or turning saw, leaving the space as at b, fig. 694; and the spaces are then pared out with the firmer chisel from opposite sides, as at c, the chisel being placed exactly on the gage lines, but slightly overhanging, so that the insides are cut hollow rather than square, to insure the exact contact at the inner and outer edges of the dovetails.
When the wood between the pins is removed entirely with the chisel, this instrument is driven with the mallet perpendicularly into the wood just in advance of the gage-line, and sloping cuts are then made to form a notch half-way through the wood as at f; and when the space has been thus cleared, a more careful vertical cut is made exactly upon the gage-line itself, as in the former case.
The dovetails are next marked from the pins, and thus become their exact counterparts. In marking the dovetails, the end piece d, fig. 695, is laid upon the bench, and the pins in p are placed exactly vertical, and in their intended positions; and lastly, the scriber is passed along the two sloping sides of every pin. The gage lines are followed with the dovetail saw, the waste of the tool being taken from the hollows, so as to leave the gage lines almost standing: the hollows between the dovetails are now removed with the chisel unless the work is very large, when, as in cutting away the wood between the dovetails, the frame saw may be previously employed.
As the gage lines are almost left in sight, the pins and dovetails are mutually a trifle too large, so that in driving them together, they somewhat compress each other, and produce that close accurate contact to be observed in good works; and which gives rise to so much surface-friction, that the glue might in some cases be nearly dispensed with between the joint; but if the pins are left too large, they split the wood.
Whilst the chisel is being employed in dovetailing, it is usual to lay the several pieces of wood upon the bench, with their ends slightly extending beyond each other, like a flight of steps, an arrangement that admits of every edge being readily seen and operated upon; the pieces are fixed in this position by the holdfast, and when they have been cut half-way through, they are turned over, and finished from the other side.
Figs. 696 to 701 represent in plan, and in one group, the several ways of dovetailing the edges of boxes and similar works: fig. 696 is the mitre and key joint, and fig. 697 the common dovetail joint already spoken of, in which the pins and dovetails are both seen from the outside of the box. In the four other kinds the parts are more or less concealed, and they may be considered to increase in the difficulty of construction, in the order in which they are represented. It is supposed that the pins which are on the upper pieces marked p, are made before the dovetails on the pieces d, and before scribing which latter from the pins, chalk is rubbed on mahogany and other dark woods, to make the lines more conspicuous.
Fig. 698 is the half-lap dovetail, which is much used for the front of drawers. The pins in p, or the front of the drawer, are first marked, and the wood is also gaged at the end to denote how far the pins shall extend inwards: the saw can only be used obliquely, as shown by the dotted line, and the pins are finished with the chisel applied on the lines a and d. When, however, the drawer front is to be veneered, the pins are often sawn quite through on the line d, as the pins may be thus more easily cut, and the veneer conceals the saw-kerfs in the drawer front. The dovetails on the sides of the drawer, or d, are afterwards marked and cut as in the first example, fig. 697, but of their exact lengths.