The double dovetail puzzle consists of two pieces of wood (usually one dark and the other light) which, upon examination, appear to be dovetailed together from each face. This interlocking arrangement is obviously impo
At are given the diagrams for setting out. Draw the outline of the elevation, plan and end view. The end view in the first instance is indicated by 3, 4, 5 and 6, and it measures 17⁄8 ins. square. A 17⁄8-ins. square is simply used because 2-ins. wood generally finishes this size after it is planed up. Set out a square (A, B, C, D) which stands corner-ways in the larger square (3, 4, 5, 6). Project the lines D A and C B upwards as at 1, and on to this drawing (1), set out the dovetail according to your own idea of length, width and bevel. Project the four points of your dovetail downwards into the end view, and where these lines cut A, B, and D, C draw them downwards and rebate them into your original plan. This will give the true shape of the two dovetails and it is to this shape that you will cut your joint.
The joint is in due course glued up, and next day you will plane and waste off the four corners of your model. The end view shows one corner shaded D, 3, A; this and the other three corners are wasted away. The result is that the dovetails are thrown into a plane different from that in which they were made, showing as .
Fig. 379.— Double Dovetail Puzzle.
Fig. 380.— The Two Parts Separated.
(Note that dovetail is cut on slant, the thickness at front being less than at back. See dotted line on plan below.)
The model calls for very accurate workmanship and the joints must not be undercut during the sawing and chiselling operations. The completed model measures 6 to 7 ins.
The Dovetail Puzzle joint illustrated at has perhaps caused more argument and controversy amongst woodworkers than any wooden joint. It may be neatly made in maple, walnut, or mahogany, and afterwards glued up. The question everyone asks is: How was it put together?
Take two pieces of wood such as mahogany, walnut or birch, about 6 ins. long by 17⁄8 ins. wide and 11⁄4 ins. thick. Truly plane them up and then set out and make the tenon and dovetailed piece . Next mark out and cut the cross bar to fit its corresponding piece. The joint will go together in a somewhat diagonal direction as it is pushed into position from the back; when closed it will appear as at . For guidance, a plan, part elevation and back elevation are added.
An improvement after you have gained experience in the making of this joint is to make a similar joint, leaving the face (B, ) blind; it then does not show the bevelling of the dovetail at the end C. In other words, keep the line C, say, 1⁄4 in. back from the face of B. The joint should be glued up and it will then appear to the average worker that it is an impossible proposition. (See , page 208.)
Carefully note that the edges A, A are parallel to each other in spite of the fact that they slope in one direction.
A further variation of the puzzle is seen in . Here the joint is much simpler, and can easily be followed from the illustration.