Fig. 192.—Dowel with Groove.
Fig. 193.—Sawing Groove in Dowel.
To plane off the corners a "cradle" is made and kept for the purpose. The advantage of this cradle is obvious, preventing as it does any tendency of the partly-formed dowel to slip or wobble. A jig, or cradle, is easily made by bevelling the edges of two separate pieces of wood and then glueing and screwing them together as at . A small block of wood is inserted to act as a stop whilst the planing operation is in progress. It is usual to bevel both edges of the timber from which the cradle is formed, thus accommodating all sizes of dowels from 1⁄4 in. to 5⁄8 in. in diameter.
shows a completed dowel with a small groove running along its entire length. The object of this groove is to allow the air and superfluous glue to escape and thus avoid splitting the work on hand; the groove also secretes a certain amount of glue, which increases its hold on the timber.
illustrates the method of marking out and gauging two boards for dowelling. The edges of the boards are first shot to a true joint; then the face sides are placed together and the lines for the dowels are marked across the edges with a fine pencil and the aid of a try square. The boards are then gauged from the face side, thus giving the points indicated in the sketch.
To start the twist bit it is a good plan to prick the board at the point of intersection of the marked lines with a sharp, circular-pointed marking awl. This obviates any tendency of the boring bit to run out of truth and thus cause unevenness on the face side of the jointed board. (See .)
A safe rule for the spacing of dowels when jointing sideboard tops, dressing table and wardrobe ends, etc., is to place the dowels 9 ins. to 10 ins. apart, and place two dowels at each end as shown at . The length of the dowels should be about 7⁄8 in. to 11⁄4 in. long.
shows the two boards prepared ready for glueing. The back one is bored to receive the dowels, and the front one shows the dowels glued in position. It is customary to warm the edges of the boards before spreading the glue, and cramps are required to squeeze the joint tight. These should be left on the jointed board from one to four hours according to the state of the weather. In cases where thick timber (say 2-in. or 21⁄2-in. boards) is to be jointed, two rows of dowels may be used, the position of the dowels being as .
shows the plan of a 3-in. cornice pole made to fit a bay window; the straight portions of the pole are generally turned in the lathe, the corner portions being afterwards jointed and worked up to the required shape. To avoid any difficulty in the setting out of the dowels, a disc of cardboard or sheet metal is made to the same diameter as that of the cornice pole; this disc is called a template. The positions of the dowels are set out geometrically, and the centres are pricked through with a fine-pointed marking awl (see sketch of template, a, ). The template is put on the ends of the straight pole, and the dowel centres are pricked into the wood. The process is repeated on the ends of the corner block (b, ), and if the holes be now bored at the centres indicated a true fit will be obtained.
Fig. 200.—Method of Dowelling Thick Timber.
Fig. 201.—Method of Dowelling Cornice Pole by Means of Template.
shows two portions of the circular pole jointed up to a corner block, and the dotted lines P indicate the direct line of pressure and shows the position for the cramp. When the glue is thoroughly set the corner block is sawn and spokeshaved to the desired shape as shown by the dotted line. This method is illustrated to show that, by the use of a suitable template, dowels may be exactly set out even when there is no straight or square face from which to use a marking gauge, and the method may, of course, be applied to many other examples of dowelling at the discretion of the workman.
Fig. 202.—Dowelling a Mitred Frame.
Fig. 203.—Method of Frame Dowelling. (Long and Short Shoulders.)
Fig. 204.—Table Leaf with Dowels.
Fig. 205.— Block for Twist Bit.
Fig. 206.—Dowelling for Moulded Frame.
Fig. 207.— Cap.
shows one corner of a mitred and dowelled frame. It needs little or no explanation beyond the fact that the dowels should be at right angles to the line of joint, and consequently the dowel at the outside edge of the frame will have to be much shorter than the others. This gives a strong and serviceable joint, suitable for many purposes.