Fig. 149. - The new tools in this exercise are the bow saw, and spoke-shave.

Gauging, edge and face planing, glueing, sawing with bow saw, and edge modelling with spokeshave are involved.

Having drawn the mat (not necessarily in isometric projeco 2 tion), two pieces of wood of contrasting colours should be cut up into the required lengths. To produce a pleasing effect to the eye not fewer than seven strips should be made, and even numbers should be avoided for the same reason.

In cutting up the strips, it should be remembered that the outer bands are shorter than those in the centre.

No dimensions are given, as the model can be made to any size, but we will assume that the wood is 1 1/2 in. wide and 3/8 in thick.

Plane up the strips true, taking care not to remove too much material. This planing, and, indeed, all the work of this exercise, should be very carefully done, as a new and somewhat difficult form of jointing is taken up.

Fig. 149.

The use of the shooting board is now introduced. The construction of the shooting board is too difficult for a beginner to attempt, because it must be accurate, or it is useless.

It is described on pp. 339-40, and when sufficiently advanced the pupil who may require one can make it himself; but at this stage it is assumed that a teacher will always make these boards for the class.

Place one of the light-coloured strips on the board, face downwards, with one end against the stop and with the edge projecting about 1/4 in. over the ledge. Lay the plane on its side, and hold it firmly against the edge of the wood to be planed, which should be pressed down with the outspread fingers of the left hand (see fig. 150); and when the plane is pushed forward, as in fig. 151, it is of the greatest importance that it should be still kept close up to the wood along its entire length. There is a tendency to push the heel of the plane slightly outward, as it is sent forward, and this should be carefully avoided, as it will result in planing away too much at the further end of the wood.

Fig. 150.

Plane up both edges of all the light-coloured strips in this way, keeping all face downwards on the board while being planed, and then shoot the edges of all the dark-coloured strips similarly, but with the face side of each piece upward while being planed.

The reason of this is that a shooting board or plane rarely gives a perfectly true right angle, though when tested by ordinary methods both the plane and the angle of the shooting board may appear correct; and if all the strips were planed with the face upwards, the amount of error would be multiplied by twelve, for both sides of each of the six joints would be affected.

Fig. 151.

The joints would be properly made, it is true, but the infinitesimal error on each side of the six joints, would result in a noticeable curve, either concave or convex, in the face of the completed mat. The plan of reversing the strips in the manner described entirely avoids this danger, and necessarily gives equally good joints.

In glueing up the strips, take care to rub the glue well out, and join them first in pairs, and then glue the pairs of strips together. Before glueing, make a cleat in which to clasp the model. The cleat should be a strip of wood about 2 ins. wide, with two blocks nailed on it, a little further apart than the extreme width of the model. Insert at one end two wedges from opposite sides, as in fig. 152. These, when driven in fairly tight, will tighten the joints, and the model can be left to dry.

Fig. 152.

When the model is again taken up, the small projecting pieces of glue should be removed with a few strokes of a jack plane, and the ellipse drawn on the surface. Before using the bow saw, take care that the blade is true, for as the handles can be turned round in their sockets at will, it is possible that in adjusting the saw, the blade may be twisted, and of course will not then cut at all well. Stretch the blade almost up to the breaking point of the back string, by turning the lever.

In using the saw, grasp it with both hands, as shown in fig. 153, and keep the saw moving with perfectly horizontal strokes, or otherwise the two sides of the cut will not be similar. In the model now being made cut in to the pencil line, at any point, and then saw the ellipse completely out, leaving about 1/8 in. of wasteen, outside the line. This waste is to be removed with the spoke-shave, as the saw would leave too rough a surface.

Fig. 153.

The spokeshave, and, in fact, any cutting tool, should, when in use, cut away from the operator. There are several reasons why this rule should be adopted. The safety of the operator, and the additional power and command when pushing any tool as compared with the reverse pulling action being the chief. Hold the spokeshave as in fig. 154, and in a horizontal position.

The surface is curved, and in pushing the tool forward make it follow the curve of the ellipse as far as possible, and do not attempt to make any part of the edge perfectly true at first, but work steadily round, removing all the irregularities, and so make a fairly even surface then go over the whole of the work again and render it quite smooth. After making the edge true, take the model out of the vice and put it on a panel board. This board is described on p. 340, and it is enough to say here that, as several small pieces of thin wood have to be tacked down to act as stops, the use of this board will save the top of the bench from being injured by nailing. Place the model against the stops and make the whole surface quite smooth with trying plane and smoothing plane. Complete the model by boring the hole in the end.

Fig. 154.