Woodwork Joints Part 9

Fig. 202 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.

FRAME DOWELLING.--Fig. 203 shows one corner of a frame with long and short shoulders, such as occurs when the upright is rebated through its entire length. The holes in both pieces are bored for the dowels before they are rebated. This avoids any difficulty in endeavouring to bore with only one side of the twist bit in the wood. A similar type of joint is used on nearly all kinds of gla.s.s and door frames in cabinet work.

Fig. 204 is a leaf for the screw type of table. Circular dowels are shown at one end, and rectangular wooden pegs at the other; both methods are equally good, and, of course, the dowels are only glued into one leaf.

The object of these dowels is to guide the table leaf into its proper position when the leaf engages the table proper, and to make the flat surface of the table top and leaf register correctly and thus ensure a level surface.

Fig. 205 is a wooden block made in two portions and held together by screws; it is used to fasten around a twist bit, the object being to ensure that all the dowel holes are of uniform depth. It may be adjusted as desired and firmly screwed round the twist bit; if the hole is made 1/4 in. in diameter it will clip round a 1/4-in. or 3/8-in. bit and will answer a dual purpose. It is a preventative for bad dowelling.

Fig. 206 is an example of dowelling framing when the moulding on the edge has to be mitred. It is necessary to cut the shoulders away so as to allow the members of the moulding to intersect. The section of the mould is not shown in the sketch for clearness of representation. The portion marked H is called the "horn," and it is not cut off until after the frame is glued up; its object is to prevent the rail splitting or bursting when knocking up the frame or during the cramping process.

Fig. 207 shows the method of dowelling a moulded cap to the top of a wooden bedstead post or similar pillar where it is desired to avoid any unsightliness.

Fig. 208 is a dining-table leg and portion of the framing, showing the method of dowelling the frame to the leg. Chairs, couch frames, etc., are made in a similar manner.

Fig. 209 shows the top portion of a table leg and a home-made dowel gauge. The gauge is made of any hardwood, and steel wire pins are driven through at the required positions and sharpened similar to the spur of a marking gauge. The legs are sawn and planed up true and square, and the advantage of the gauge is that all legs are marked exactly alike and are therefore interchangeable until glued up. A gauge of this type is easily and quickly made and may be kept for its specific purpose or altered for other work.

Fig. 210 indicates the Queen Anne type of leg, a sketch of same broken below the knee also being given. Here we have another type of irregular setting out, which is accomplished in the following manner. Saw and plane the broken portion of the leg true as shown; take the timber which is to be jointed and treat it in a similar manner; now place four ordinary pins on the lower portion. Carefully place the top portion to the required position and smartly give it one tap with the hammer; this will cause the pin-heads to leave indentations, and if these be taken as centres for boring, accurate work will result. The new portion of the leg is afterwards sawn and wrought to the desired shape.

This is an example of work where it is next to impossible to use a gauge, and as only one joint is required it is not worth the time taken to make a template.

[Ill.u.s.tration: Fig. 208.--Dowelling a Dining-Table Leg.]

[Ill.u.s.tration: Fig. 209.--Dowel Gauge for Legs.]

[Ill.u.s.tration: Fig. 210.--Dowelling a Cabriole Leg.]

The tools used in dowelling are: Brace, countersink, dowel-rounder, twist bit, try-square, marking-awl, and the usual bench tools. The first four are ill.u.s.trated at Figs. 194, 195, 196 and 197 respectively.

The method of working is: Plane up, mark out, bore holes, countersink, glue dowels and complete joints.

THE SCARF JOINT

The method known as "scarfing" is used for the joining of timber in the direction of its length, enabling the workman to produce a joint with a smooth or flush appearance on all its faces. One of the simplest forms of scarfed joint is known as the half lap, in which a portion is cut out at the end of each beam or joist, equal in depth to half the full depth of the beam, and of equal length to the required scarf.

The two pieces before they are placed together form a joint as shown at Fig. 211, the projecting part (A) fitting into the recessed portion marked B and the two pieces being secured in their respective positions by screws.

Fig. 212 shows a dovetailed scarf joint. This is a variation of Fig. 211, the length of the dovetail lap being from 6 ins. to 8 ins. in length.

Fig. 213 is an ill.u.s.tration of a joint designed to resist a cross strain.

The face side is left flush, whilst the underside is a.s.sisted by an iron plate. The joint is secured with nuts, bolts, and washers. This type of joint is frequently used for joining purlins in roof work; the iron plate on the underside is in this case omitted.

Fig. 214 is designed to resist both tension and compression and is an excellent joint for all purposes. The joint is brought together by using folding wedges as shown in the centre.

[Ill.u.s.tration: Fig. 211.--Half-Lap Scarf Joint for Light Timber.]

[Ill.u.s.tration: Fig. 212.--Dovetailed Scarf Joint.]

[Ill.u.s.tration: Fig. 213.--Plated Scarf Joint Used in Roof Work.]

Fig. 215 is a variation of Fig. 214, and it will be noticed that tenons are provided on the face and underside to resist cross strain. Probably this is one of the best varieties of the scarfed joint. Unfortunately, however, its production is somewhat costly, and this may be the reason that it is not more universally used. Folding wedges are used to secure the two pieces in position.

[Ill.u.s.tration: Fig. 214.--Tenoned Scarf Joint.]

[Ill.u.s.tration: Fig. 215.--Double Tenoned Scarf Joint.]

[Ill.u.s.tration: Fig. 216.--Scarf Joint with Vee'd ends.]

Fig. 216 is a scarfed joint with undercut vee'd ends which prevent the joint from lipping up or down or sideways. It is a useful joint, calling for careful setting out and accurate craftsmanship. Folding wedges are used in this case to draw up and secure the joint.

Fig. 217 is a "fished joint," and the following difference between a scarfed and fished joint should be noted. A fished joint need not necessarily reduce the total length of the beams to be joined, and fish plates of wood or iron (or a combination of both) are fastened at each side of the joint. In a scarf joint all surfaces are flush. In Fig. 217 the beams are b.u.t.t-jointed and secured by wooden plates and iron bolts.

The upper plate is let into each beam, and the lower plate is provided with two wooden keys to prevent the beams sliding (or "creeping") upon the lower plate. Iron nuts, bolts, and washers are used to complete the joint.

[Ill.u.s.tration: Fig. 217.--Fished Joint.]

In the case of the scarfed joint at Fig. 218 (used for purlins) the length of the scarf is usually made about four times that of the depth of tie beam. It has two hardwood keys which force the pieces together and thus tighten the joint.

[Ill.u.s.tration: Fig. 218.--Detail of Scarfed Joint in Purlins.]

The methods of scarfing and fish-jointing are many and varied, and, in selecting a joint, the nature of the pieces to be joined and the direction and the amount of the load should be carefully taken into consideration.

The above joints come under the heading of carpentry, and the ordinary tools such as the saw, plane, boring-bit and chisels are all that are requisite and necessary to produce a sound and serviceable joint. Scarfed joints are generally of large size, and they are usually made by placing the work upon sawing trestles owing to the bench being too small to accommodate the large timbers.

[Ill.u.s.tration: Fig. 219.--Example of Tabled Joint with Straps.]

[Ill.u.s.tration: Fig. 220.--Lapped Scarf Joint with Bolts for Heavy Timber.]

Fig. 219 is a tabled scarf joint which admirably resists tension and compression. It is very easy to make and fit, and is not materially affected by shrinkage. The rectangular wrought iron straps are knocked up over the joint after the two pieces engage. The length of the joint should be approximately five times its thickness.

Fig. 220 is an example of a lapped scarf joint which is secured with nuts and bolts. It effectively resists compressional stress in vertical posts and it may, if required, be strengthened by the addition of wrought iron fish plates. It is quite a serviceable joint for all general purposes, such as shed or garage building where fairly heavy timbers are used.

THE HINGED JOINT

One of the most common forms of hinged joint in use to-day is that formed by using the "b.u.t.t" hinge, and many troubles experienced by the amateur, such as "hinge-bound," "stop-bound," and "screw-bound" doors, etc., are due to a lack of knowledge of the principles of hingeing. Hinges call for careful gauging and accurate fitting, otherwise trouble is certain to occur.

A "BOUND" door or box lid is said to be hinge-bound when the recess which contains the hinge is cut too deep. The frame and the body portion engage too tightly when closed, the result being that the door has always a tendency to open a little. This fault may be in many cases remedied by packing behind the hinge with one or two thicknesses of good stiff brown paper. For packing purposes such as this paper will be found to be of much more value than thin strips of wood or knife-cut veneer, the latter always having a great tendency to split when a screw or bradawl is inserted.

A stop-bound door is the name applied when the door is not finished to exactly the same thickness as originally intended. This causes the door to bind on the stops at the back, as shown at Fig. 221. The difficulty may be remedied by thinning the door a little at the back, or slightly rounding away the portion which binds.

Screw-bound is a common fault often overlooked by the amateur. It is caused by using screws of which the heads are too large for the countersunk holes in the hinge, and may be avoided by slightly sinking the holes in the bra.s.swork with a countersink or rose-bit.