How to Make Dovetail Joints
Instructions and tips on how to make a dovetail joint.
We now come to the consideration of the method of corner-jointing known as the dovetail; but, on account of the trouble and difficulty attending its satisfactory execution, it is not likely to be much resorted to by the amateur joiner. Under this conviction, we have entirely avoided introducing the joint in the construction of the articles of furniture represented in the plans of this manual. At the same time, it must be acknowledged that no treatise on joinery, however elementary, would be passable without containing some instructions in the methods of forming the dovetail joint.
In the diagrams here given are shown the two treatments of the joint in ordinary use. That represented, in its divided state, in diagrams A and B is called the lap-dovetail, which shows when complete the jointing on one side only: and that represented, in a similarly divided state, in diagrams C and D is the common-dovetail, which displays its construction on both sides of the corner.
Types of Dovetails
The lap-dovetail joint is invariably used in the fronts of properly made drawers or furniture of a similar and well-finished character. The common-dovetail is used where strength is required and appearance is of less importance in the furniture: it is quite suitable if closely made for work that is to be painted. It may be said, however, that from an artistic point of view, and when the display of truthful construction is desired, there is nothing to be said against carefully made dovetail joints of this common form. This form may be described first.
Common Dovetail Joint
When the boards to be dovetailed have been dressed to the required thickness, and their ends properly planed true and square, a marking-gauge must be set so as to scratch a light line along each side of the ends of both pieces, about a twentieth of an inch farther from their edges than the thickness of the wood : this excess is to allow a final dressing off when the joint has been glued. The next process is to carefully draw on the piece D the forms of the dovetails, setting out the measurements uniformly, and using a try square & mitre square, the mitre being adjustable, in marking the lines for the saw-cuts. When this has been done, the piece must be fixed vertically in the bench-vise, and the cuts accurately made with the dovetail saw, down to the gauge marks on both sides.
The piece must now be removed from the vise, laid flat, and the proper portions cut out with a small firmer-chisel. Should any irregularities obtain where sawn, they must be pared true with a chisel.
The other piece of wood (which has to be cut as shown at C) must now be fixed in the bench-vise, with its edge about level with the top surface of the bench, and the dovetailed end of the piece D laid accurately in position upon it. The shapes of all the dovetails must now be closely scratched on the end of the uncut piece with a sharp marking awl. When all the additional lines have been scratched, down to the gauge marks on both sides, using the try-square as a guide, the cuts may be made, and the larger pieces removed with a firmer-chisel. Care must be taken in sawing to keep free of the dovetail lines scratched on the end of the piece, otherwise a loose joint may be made, without any means of altering it: on the other hand, a too tight joint can very easily be put right with the chisel.
In forming the lap-dovetail joint exactly the same process must be adopted in forming the end of the piece B as described above in connection with the piece D, with this exception, that the gauge marks must be made at a distance from its edges equal to the thickness of the piece A, less the thickness of its lap, as clearly indicated in the diagram. The same gauge that marked the depth of the cuttings in the piece B must now be drawn along the end of the piece A, so as to define its lap, and the limit of its dovetail sinkings.
The finished dovetails of the piece B must be accurately adjusted upon the end of the piece A, and their forms scratched thereon, in the manner already described for the piece C. After-scratching the inner straight lines of the sinkings, down to a gauge-line marking the depth of the sinkings, a trifle more than the thickness of the piece B, the sinkings (or "pockets", as they are sometimes called) can be cut out. A certain amount of the cutting may be done with the dovetail-saw, but the chief amount must be done with firmer-chisels, care being taken to secure a neat and tight joint. Glue both pieces, and gently drive the joint tight, using a piece of flat board between the hammer and the joint. When the glue is dry, the end of the piece A must be carefully dressed off flush with the face of the piece B.
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