Part 12 (1/2)

Fig. 266 shows a shutting joint used to prevent permeation of dust to the interior of a drawer. The drawer front is grooved and engages a suitably-formed slip which is screwed to the bearer as indicated in the ill.u.s.tration. Occasionally some difficulty is experienced when fitting the slip to a narrow drawer, but this can always be overcome by putting in the screws from the top of the bearer instead of from underneath.

[Ill.u.s.tration: Fig. 266.--Dust-proof Drawer, showing the Front grooved to engage a Slip which is screwed to the Bearer Rail.]

Shutting joints which are required to be ”light-tight,” such as those used in photographic work, are generally formed by slightly grooving the frame and inserting a strip of black velvet. The friction of the high pile of the velvet prevents the filtration of light through the joint.

When making air-tight showcases, one of the best and simplest tests is to place a lighted candle in the case and close all the doors; if the candle goes out within three minutes you have accomplished your object.

THE DOVETAIL JOINT

Nothing definite is known as to the origin of dovetailing, but a quaint and pleasing little story which is well worth repeating runs as follows: A farmer had called in the local ”joyner” to do sundry repairs at the homestead. One day, whilst enjoying a humble meal, he sat watching some doves as they hopped about the yard. Struck by the movement of their wedge-shaped tails, it occurred to him to joint his timber by the interlocking method; hence we have _dovetails_.

[Ill.u.s.tration: Fig. 267.--A Single Through Dovetail.]

[Ill.u.s.tration: Fig. 268.--Through Dovetails on Carcase Work (P, Pins; T, Tails).]

THROUGH DOVETAILING.--One of the simplest forms of the dovetail joint is shown in Fig. 267, where two pieces of timber are joined by the method known as ”through” dovetailing. This method is used in everyday practice for joining the corners of frames, bracket trusses, and a hundred and one other articles.

Figs. 268 and 269 show the method of through dovetailing as applied to the making of boxes, plinths, and general carcase work; it is used in positions where no objection can be taken to the end grain showing on each side of the finished work. In the case of plinths and furniture cornices the foundation frame is made of yellow pine or other cheap wood, and the more expensive and rare timbers are glued and mitred around in various thicknesses and shapes, thus saving the more costly material and strengthening the construction by the method known as laminating. In many cases all that is necessary is to veneer the face sides, thus covering and hiding any unsightliness.

[Ill.u.s.tration: Fig. 269.--Dovetails for Boxes, etc.]

[Ill.u.s.tration: Fig. 270.--Lap-dovetailing for Drawers.]

LAP-DOVETAILING.--Fig. 270 is an example of lap-dovetailing, such as is used where a drawer side joins with the drawer front. It is not permissible to allow the end grain of the timber to show at the front of a drawer, and this is why resort is had to the lap-dovetail. As the most general use of the dovetail is for this and similar purposes, we shall therefore deal fully with the methods of marking out and the making of this cla.s.s of joint.

ANGLES.--A most important point in the construction of a dovetail is to avoid having the angles of the pins and tails too acute. An inclination of one in eight is considered correct; no hard and fast rule need be obeyed, but the variation should on no account be less than one in six.

[Ill.u.s.tration: Fig. 271.--How to obtain Correct Angles for Dovetail Template.]

[Ill.u.s.tration: Fig. 272.--Squaring and use of Template.]

Fig. 271 shows a simple method to obtain the correct angle. Take a piece of timber and plane up the face edge (A, B) true and straight; mark out a line (C, D) at right angles to the face edge and s.p.a.ce off 8 ins. as shown; now measure a distance of 1 in. (D, E), and join E to point eight.

This will give the correct angle for the dovetails, and it may then be transferred to the joiners' bevel. Many workers who are constantly on dovetail work make a zinc template to the exact angle and keep it specially for the purpose (Fig. 272).

SQUARING.--Another important point to remember is that the drawer sides must be true and squared to an exact length and planed up to thickness; otherwise the finished drawer will be in winding and out of truth.

To true and square the ends of drawer sides, drawer backs and drawer front, a most useful little machine is the mitre trimmer; failing this, excellent results can be obtained by using the shooting board.

[Ill.u.s.tration: Fig. 273.--Method of Marking with Cutting Gauge.]

GAUGING.--After squaring up the timber accurate gauging of the ends is another important point. The gauge used should be a cutting gauge, so that the line is incised about 1/32 in. in depth, thus effectually cutting the cross fibres of the timber.

Fig. 273 shows the method of using the cutting gauge. The stock of the gauge must be held well up to the end of the timber. The gauge is a most difficult tool for the novice to use, and his trouble is generally caused by holding it too flat. Tilt the gauge a little so that the thumbscrew shown in the ill.u.s.tration goes nearer to the floor; the blade will then not bite so keenly, and better results will be obtained. The dotted lines indicate the positions which the dovetails will occupy when marked out.

The gauge is set a trifle less than the thickness of the drawer sides to allow for the thickness of the steel cutter, and a gauge line is marked on the inside of the front and all round the drawer back. The gauge is now readjusted so as to leave a 1/4-in. lap on the front, and a line marked on the ends of the front and all round the ends of the sides which will engage the drawer front. A glance at Figs. 270 and 273 will make this clear.

[Ill.u.s.tration: Fig. 274.--Removing the Waste Wood.]