Woodwork Joints Part 8

To saw the tenons, place the rail in the vice as at Fig. 179 and, with a panel, tenon, or hand saw, according to the size of the work, cut down the outside of the tenon line as shown. Reverse your position and cut as shown at Fig. 180, then place the rail in a vertical position, and you will find little or no difficulty in sawing down square with the shoulder line. Repeat the above methods of sawing until all the tenons are sawn.

Next saw out the pieces at the side of the tenon by the following procedure. Place the rail against the bench stop, or in the vice, and cut a small channel in which to run your tenon saw as shown at Fig. 181. If you have scored the line deeply with your knife when you were marking out the work, you will have little difficulty in removing a small portion with the chisel. The amount removed in the ill.u.s.tration is, of course, exaggerated. In the small channel thus made place the tenon saw and, guiding the saw blade with the finger so as to keep it upright or square (Fig. 182), saw away the waste material. Remove the waste material at the sides of the tenons in a similar way, and then saw out the portion marked H, Fig. 177, lower sketch.

THE MORTISING of the stiles may next be taken in hand by putting the stiles edgeways in the vice and boring away the bulk of the waste wood from the mortise with a suitable-sized twist bit and brace. This method will save a great amount of noise, as to a great extent it does away with the use of the mallet. Take the mallet and chisel and chop down about 3/8 in. as shown at Fig. 183; then turn the chisel to the position shown at Fig. 184 and remove the small piece as shown. Continue these two operations until you are about half-way through the wood and then start in a similar manner at the line _a_, Fig. 183, after which turn the other edge of the timber uppermost and repeat the methods shown.

[Ill.u.s.tration: Fig. 182.--Sawing away Waste Material.]

[Ill.u.s.tration: Fig. 183.--Using the Chisel and Mallet for Mortising.]

Fig. 185 shows the sketch of a mortise which has its side removed so as to show the method of successive cuts with a chisel when removing the core from a mortise; this, in conjunction with the other sketches, clearly shows the methods of working. In many woodwork examinations the examiners insist that the mortise shall be removed by successive cuts with the chisel, but we certainly advise the removal of much of the waste wood with a boring bit, provided the worker can keep straight and well within the limitations of his gauge lines.

[Ill.u.s.tration: Fig. 184.--Removing Waste of Mortise with Chisel.]

REMOVING HAUNCHING.--After removing the mortise hole, the small portion which is called the haunching will require to be removed with a chisel.

This calls for no special remark, as it is clearly shown in Figs. 187 and 188. Fig. 186 shows an everyday type of mortise and tenon joint separated; it is used in cases where a straight joint is required on the upper or lower edge of the work, whereas the upper rail of Fig. 176 shows the full haunch on the top edge. In cases such as Figs 187 and 188, where the edges of the frames are grooved to receive panels, etc., the width of the tenon is reduced by the width of the groove.

[Ill.u.s.tration: Fig. 185.--Mortise with Side Removed.]

[Ill.u.s.tration: Fig. 186.--The Joint Separated.]

[Ill.u.s.tration: Fig. 187.--Removal of Haunching.]

[Ill.u.s.tration: Fig. 188.--Haunching with Groove above.]

This must be remembered by the worker when marking out his stiles with the marking knife. Fig. 187 (right-hand sketch) shows the haunch, tenon, and groove G at the bottom. Fig. 188 (left-hand ill.u.s.tration) shows G (groove) at top, and HH (the haunch) at the bottom. Tenons may be glued together and wedged as shown at Fig. 176 if for inside work; but if for outside work they are generally smeared with thick paint and wedged up.

For light-cla.s.s cabinet work it is usual to cut the mortise about seven-eighths of the distance through the stile and make the tenon to match it; the edge of the finished work does not then show any indication of the joint, and it leaves a nice clean surface at the edge of the work for polis.h.i.+ng or varnis.h.i.+ng.

[Ill.u.s.tration: Fig. 189.--Interlocking Joint for Seat Rails of Chair to Leg.]

INTERLOCKING CHAIR JOINT.--A joint designed with a view to strengthening the construction of chairs at the point where they are weakest is shown in Fig. 189. The joint is an interlocking one so arranged that, once the chair is glued up, no motion of the side rail can be possible. The groove in the side rail tenon is cut in such a manner that, on the insertion of the back rail tenon, the joint actually draws up and, having done so, is locked in position. The exact location of this groove is obtained in a similar manner to that used in marking out tenons for drawbore pinning, _i.e._, the tenon is inserted in its mortise and the position of the back rail mortise transferred to it, after which the lines are set back by 1/64 in. (approximately) to cause the joint to draw.

From the ill.u.s.tration the construction of the joint should be clear. The method is particularly adapted to a section of rectangular form where one side is longer than the other, such as the back leg of a chair, as this shape allows for the accommodation of the extra length of tenon required.

THE DOWELLING JOINT

Dowelling is the term generally given to the method of jointing timber and other materials by wooden or metal pegs, which are called dowels. For cabinet-making and similar work straight-grained beechwood dowels are mostly used; these may be bought by the gross, in lengths of about 36 ins., and of any desired diameter.

[Ill.u.s.tration: Fig. 190.--Steel Dowel Plate.]

MAKING DOWELS.--Many, however, prefer to make what they require for the work in hand, and the following is the method that is generally employed.

Pieces of straight-grained wood are wrought to a square section, after which the corners are planed away to form an octagonal section. The sharp corners are now planed away, and the roughly formed dowel is driven through a steel dowel plate, Fig. 190, by the aid of a heavy hammer, thus giving the necessary roundness and finish to the dowels. When hammering dowels through a plate the hammer should on no account be allowed to come in contact with the face of the dowel plate, or the cutting edge of the hole will be spoilt. Simply drive the dowel to within 1/8 in. of the plate and knock it out with the next dowel.

[Ill.u.s.tration: Fig. 191.--Cradle for Planing Dowels.]

[Ill.u.s.tration: Fig. 192.--Dowel with Groove.]

[Ill.u.s.tration: Fig. 193.--Sawing Groove in Dowel.]

To plane off the corners a "cradle" (Fig. 191) 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 s.c.r.e.w.i.n.g them together as at Fig. 191. 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.

[Ill.u.s.tration: Fig. 194.--p.r.i.c.king the Centres ready for Boring. Also showing how Brace is used in conjunction with Try Square.]

Fig. 192 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.

Fig. 198 ill.u.s.trates 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.

[Ill.u.s.tration: Fig. 195.--Countersink.]

[Ill.u.s.tration: Fig. 196.--Dowel Rounder.]

[Ill.u.s.tration: Fig. 197.--Twist Bit.]

To start the twist bit (Fig. 197) it is a good plan to p.r.i.c.k 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 Fig. 194.)

A safe rule for the s.p.a.cing 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 Fig. 198. The length of the dowels should be about 7/8 in. to 1-1/4 in. long.

Fig. 199 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 2-1/2-in. boards) is to be jointed, two rows of dowels may be used, the position of the dowels being as Fig. 200.

[Ill.u.s.tration: Fig. 198.--Marking and Gauging Boards for Dowelling.]

[Ill.u.s.tration: Fig. 199.--Dowelled Joint ready for Glueing.]

Fig. 201 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 p.r.i.c.ked through with a fine-pointed marking awl (see sketch of template, _a_, Fig. 201). The template is put on the ends of the straight pole, and the dowel centres are p.r.i.c.ked into the wood. The process is repeated on the ends of the corner block (_b_, Fig. 201), and if the holes be now bored at the centres indicated a true fit will be obtained.

[Ill.u.s.tration: Fig. 200.--Method of Dowelling Thick Timber.]

[Ill.u.s.tration: Fig. 201.--Method of Dowelling Cornice Pole by Means of Template.]

Fig. 201 _c_ 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 ill.u.s.trated 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.

[Ill.u.s.tration: Fig. 202.--Dowelling a Mitred Frame.]

[Ill.u.s.tration: Fig. 203.--Method of Frame Dowelling. (Long and Short Shoulders.)]

[Ill.u.s.tration: Fig. 204.--Table Leaf with Dowels.]

[Ill.u.s.tration: Fig. 205.--Block for Twist Bit.]

[Ill.u.s.tration: Fig. 206.--Dowelling for Moulded Frame.]

[Ill.u.s.tration: Fig. 207.--Cap.]