Woodwork Joints Part 14

SAW WORK.--Take a marking awl, or a knitting needle which has had its end sharpened, and mark the lines of the dovetail in a similar manner to that shown at Fig. 307. Remove the piece A, Fig. 305, and the lower piece shown at Fig. 305 will clearly show the marks _aa_ as they appear in Fig.

306. Place the piece (Fig. 306) in the vice, and saw _outside_ the lines AA, as shown in Fig. 308.

[Ill.u.s.tration: Fig. 307.--Marking Dovetails with Marking Awl.]

After sawing down the lines AA, Fig. 308, place the wood in the vice and, guiding the saw blade with the index finger of the left hand, cut away the small piece at the side (see Fig. 275). Repeat the operation as may be necessary, and the completed joint will be similar to that shown at Fig. 300. If the sawing is not neatly done it may be found necessary to pare the shoulder with a sharp chisel.

DRAWERS.--When dovetailing drawers or boxes it is necessary to square up the ends of all the stock and gauge them, as shown at Fig. 273. This ill.u.s.tration shows how to gauge the lines on a drawer side; the dovetailed joint in this case, however, does not run through the drawer front and leave the work unsightly, as the joint at Fig. 300 would do.

The method used is shown at Fig. 309, and it is commonly known as lap-dovetailing. Most workers cut the dovetail pins on the drawer fronts and the drawer backs first, after which they mark the drawer sides with the marking awl. The dovetailing of the drawer back is shown at Fig. 310.

This is the type known as "through dovetailing," the method being similar in regard to tool operations as the single joint shown at Fig. 300.

[Ill.u.s.tration: Fig. 308.--Sawing the Dovetails.]

[Ill.u.s.tration: Fig. 309.--Lap-dovetailing Drawer Front to Drawer Side.]

[Ill.u.s.tration: Fig. 310.--Through Dovetailing.]

[Ill.u.s.tration: Fig. 311.--Chipping Waste of Lap Dovetail.]

When the pins on the drawer front have been sawn, the waste material is cut away, as at Fig. 311. First stab down with the vertical chisel, which must make the cut about 1/32 in. in front of the gauge line (see ill.u.s.tration). This commencing of the cut slightly in front of the gauge line is a very important feature. The chisel may be likened to a wedge, and if the chisel edge be placed exactly upon the gauge line and force be applied to the handle, it will force the timber away equally on each side of the gauge line, and the finished depth of the hole will therefore be too deep for the thickness of the drawer side; in other words, it will press itself over the gauge line on both sides.

By taking the first vertical cut on the waste side of the gauge line, and then removing a small piece with the chisel held obliquely, as at Fig.

311, the wood is removed and less resistance is offered to the chisel when the next vertical cut is made. This overshooting the gauge line is a common fault with the beginner, who is puzzled at the result because he is certain he had his chisel exactly on the gauge line when he commenced his vertical cut. It is especially noticeable in soft-grained woods.

To cut away the waste of a lap-dovetail (Fig. 311), the vertical and oblique cuts are repeated until the final tr.i.m.m.i.n.g up is required, and now is the time to finish both the vertical and the horizontal cuts exactly on the gauge lines.

Some workers prefer to cut the drawer sides first, and if this method is preferred (and it has its advantages for cheap work) several drawer sides are cut at once by placing four or six behind one another in the vice and sawing them all at one operation.

The drawer front is placed in the vice, and the drawer side held upon it, whilst the saw blade is placed in the saw kerf and drawn smartly forward.

This will give the required marks at the exact position desired. It must be remembered, however, to saw just inside these dovetail-pin lines, otherwise the finished joint will be too slack, owing to the removal of the sawdust, which is practically equal to the thickness of the saw blade.

MACHINE-MADE DOVETAILS.--As a general rule machine-made drawer and box dovetails show both the pins and the tails of exactly the same size. The reason is obvious after an inspection of Fig. 314, which shows the position in which the pieces are held during the machining operations. In spite of a certain amount of prejudice they are satisfactory and thoroughly reliable and have their place in modern shop and office fittings.

[Ill.u.s.tration: Fig. 312.--Machine-made Drawer Front and Side, Apart.]

[Ill.u.s.tration: Fig. 313.--The Parts Together.]

[Ill.u.s.tration: Fig. 314.--Position when Machined.]

DOVETAIL GROOVING

The dovetail housing joint should first be carefully marked out with a marking knife, so as to cut across the fibres of the wood. For obtaining the bevel on the edge of the wood a joiner's bevel may be used, and the angle should not be too acute. (See previous chapter.) Take a chisel and pare away a small channel as at A, Fig. 315, to form a small shoulder to guide the saw.

[Ill.u.s.tration: Fig. 315.--Paring away Channel for Dovetail Grooving.]

With a fine tenon or dovetail saw, cut the saw kerf as at Fig. 316. If any difficulty is experienced in cutting the kerf true and square, you may resort to the method shown at C, Fig. 315; a small temporary piece of timber has been screwed on the top of the work to form a guide for the saw.

[Ill.u.s.tration: Fig. 316.--Cutting the Saw Kerf.]

[Ill.u.s.tration: Fig. 317.--Old Woman's Tooth Plane.]

[Ill.u.s.tration: Fig. 318.--Guide Block for Bevelling.]

Fig. 315, B, shows the small channel formed by the chisel prior to the sawing operation. The sawing of the bevelled side is worked in a similar manner; but occasionally we find amateurs who adopt the method shown at Fig. 318. A block of wood (H) is first made by boring a 1-1/4-in. hole through its entire length, and afterwards making a saw cut at the desired bevel. The object of this block, which is kept specially for the purpose, is to form a guide for those who have not full control of the dovetail saw; the back of the saw clears the hole, and the required bevel is obtained. When a saw cut has been made at each side of the groove, the surplus timber is pared away in the following manner: Cut away portion E, Fig. 319; then cut away portion F, and lastly cut away the apex portion marked G. Continue by this method of paring until the approximate depth is reached. To ensure a correct depth throughout the entire groove, the router plane (or, as it is often called, "the old woman's tooth plane,"

Fig. 317) is used.

[Ill.u.s.tration: Fig. 319.--Showing Method of Paring.]

[Ill.u.s.tration: Fig. 320.--Channelling the Alternate Piece.]

With regard to cutting the alternate piece, it is necessary to first plane the end of the shelf true and square. With a cutting gauge strike the line K, Fig. 320; the required bevel on the edge (J) is then set out, and with the chisel a small channel is again formed. With the tenon or dovetail saw cut down the line K to the required depth, and carefully pare away the wood with a sharp chisel to the correct shape.

THE MITRED JOINT

Although mitreing is used in everyday woodwork, it comes last in our list of regular joints simply because it has been partly dealt with in almost every previous chapter. For example, we have mitre halving in Fig. 34, a mitre bridle joint in Fig. 74, a tongued and grooved mitre in Fig. 116, mitred mortise and tenon joints in Figs. 148 and 159, a dowelled mitre frame in Fig. 202, and a mitred dovetail in Fig. 286.

[Ill.u.s.tration: Fig. 321.--Mitred Skirting.]

[Ill.u.s.tration: Fig. 322.--Curved Mitre.]

[Ill.u.s.tration: Fig. 323.--Halving the Angle.]

MITREING.--The term mitreing is generally used to denote the type of joint used at the corner of a picture frame; or where two pieces of wood are bevelled away so as to fit each other, as the skirting or plinth mould at Fig. 321. In these cases the timber is cut so that the joint is at 45 degrees to the face, and the two pieces, when placed together, form an angle of 90 degrees (a right angle).

The term mitreing, however, is not confined to the fitting of timber around a right angle; it may be justly applied to the fitting of a moulding around an angle irrespective of the number of its degrees.

One often hears such terms as "a half mitre," used to denote the fitting of a moulding around an octagonal column or pedestal, and probably it would be more correct to describe the joint as a mitre cut at 22-1/2 degrees. Mitreing consists of halving the angle and making each piece to fit the line of bisection. Should the angle be bounded by straight lines, as at Fig. 321, then the mitred joint will be a straight line, but should the angle be bounded by a curved and a straight line, as at Fig. 322, A, or by two curved lines, then the mitred joint will have to be a curved line if the mouldings are to be of the same section.

[Ill.u.s.tration: Fig. 324.--Sawing Block for Mitreing.]

FINDING THE ANGLE.--For straight mitres, the mitre joint line is found by bisecting the angle, as shown in the various examples, and the following instructions are given to enable the reader to follow the diagram (Fig.

323). Take a pair of compa.s.ses, or dividers, and with any convenient opening strike out the arc A, B. Put the point of the compa.s.ses on A, and mark another arc C; then, without altering the distance between the points of the compa.s.s, put the point on B, and mark the arc D. Draw the line E from the corner, so that it cuts through the intersection made by the arcs C and D. The angle A B is now halved by the line E, and this method may be applied to any angle.

SAWING BLOCK.--For sawing mouldings, etc., to their approximate shape, a home-made sawing block is generally used, as shown at Fig. 324. Two pieces of wood are glued one on the top of the other, the required angle is transferred thereto, and the saw kerf made. In the sketch the saw kerfs are shown at 45 degrees, right and left, and other angles and kerfs may be made where desired.

PLANING.--After sawing the piece to approximately the correct angle, it is necessary on high-cla.s.s work to plane the cut end so as to give a perfect finish and enable a glued joint to be made. This may be accomplished by using the plane on the shooting board, as shown at Fig.

325, and, if the worker is constantly using mitres of various angles, it is an easy matter to make new angle blocks and fix them on to the board.

Other workers prefer the screw mitre trap shown at Fig. 326. This apparatus takes wide plinth or cornice moulds, and the angle may be altered by fitting temporary packing pieces under the work so as to tilt the moulding to the desired angle. The method of using the plane is indicated in the ill.u.s.tration.

Another method in everyday use by those workers who are constantly mitreing wide pieces of stock at 45 degrees is the "donkey's ear"

shooting board ill.u.s.trated at Fig. 327. The plane is laid on its side on the surface of the board marked A, and used in a similar manner to that shown at Fig. 325.