Cross-Cut Saw. As has been already explained above, and as is clearly indicated by its name, this saw is intended for the cutting of wood across the grain at right angles to the direction of the fibers. It differs from the rip saw prin cipally in the size and arrange ment of the teeth, those of the cross-cut saw being smaller, usu ally numbering about eight to the inch. The shape of the teeth in the two kinds of saws is also different, as the front of the tooth in the cross-cut saw, instead of being straight as in the rip saw, is inclined backward at an angle of about 115 degrees, while the back of the tooth slopes at an angle of about 125 degrees. The slope of the teeth should be varied according to the hardness of the wood to be sawed, those given above being suitable for soft wood. The bevel on the front of the tooth should also be varied according to the hardness of the wood, so as to give a more or less sharp cutting edge. In the saw described above this bevel should be about sixty degrees, while for harder wood it should be as much as seventy-five degrees. In general, the harder the wood to be cut, the smaller should be the teeth of the saw. Fig. 21 shows a cross-cut saw with the slope of the teeth indicated, and Fig. 22 shows how the teeth should be filed. The cross-cut saw is also known as the "panel saw." Hand Saw. There is a saw, which is much used for general work, which combines the qualities of the rip saw and the cross-cut saw. It is called the "hand saw," and is a cross between the other two. It may be used for either cutting with the grain or against it, but in any case does not do such good work as the special saw which is intended for the particular kind of work which is at hand.
Back Saw. Fig. 23 shows a saw which is known as a back saw, probably because of the extra piece on the back which limits the depth to which the saw will cut. It is also called a "tenon saw." There are a number of different kinds, varying in the width of the blade and in the length of the saw, and they are used for various special purposes, usually in miter boxes and for sawing bevels on moldings. Fig. 24 shows the arrangement of the teeth on a - - - back saw. It will be seen that the front of the tooth is nearly straight, and that the slope of the back is very sharp, making the number of teeth to the inch more than in the rip or cross-cut saws.
Keyhole Saw. Fig. 25 shows a set of saw blades which are intended to be fastened in turn to the same handle and used for various purposes. These blades are very thin and can be used for cutting out small holes such as keyholes, and it is for this reason that such saws are called "keyhole saws." The teeth are in general similar to those of the back saw, but are usually smaller.
Great care must be exercised in the filing of a saw, to give it the proper "set" to enable it to do the work required of it, and this work is better left to an expert. Most carpenters, however, like to
know how to file their own saws and to keep them in good condi tion. A great deal has been written on this subject both in books and in trade papers, but it is almost impossible to describe, in writing, the proper methods. It is a part of the carpenter's trade which must he learned by experiment and by watching the older workmen.
Planes. Timber comes from the mills rough from the saw, and before it can be used for any finished work it must be prepared to receive paint or other kinds of finish. This preparation consists in a smoothing or planing which can be carried to any extent, including sandpapering or even polishing. The instruments used for the rougher part of this work are called planes, after which, if more smoothing is required, come scrapers and sandpaper. There, are a great many different kinds of planes, but the principle of all of them is the same. They consist of a sharp blade, or knife, in the form of a chisel, which is held in a large block of wood or iron by means of clamps, so that the knife can be kept steady and guided easily. The knife projects at the bottom of the back through a slot, and takes off a shaving which is larger or smaller according to the projection of the knife. For smoothing, the cutting edge of the knife must be absolutely straight and must be clamped into the block in such a way that the projection will be exactly the same all along the edge. Any imperfections in the edge of the knife will be repeated on the surface of the wood. Planes are in general of two kinds, namely, "jack planes" and "trying planes." Jack Planes. The jack plane is used for the rougher work to give the preliminary smoothing after the lumber comes from the mill. It is bigger and, as a rule, heavier than the finishing planes, and is almost always made of wood, while the others are often made of iron. Fig. 26 shows a view of a jack plane. The handle is neces sary to push the block forward, and it is usually necessary to bear down heavily on the forward end of the. block to keep the knife down into the wood.
Trying and Smoothing Planes. The smoothing plane is usually much smaller than the jack plane, as it is not expected to take off so much material and there does not have to be so much leverage.
1 n construction it is similar to the jack plane, and may be made of either wood or iron. Very often, however, it is without a handle, as no great force is required to oper ate it. The trying plane is longer than the jack plane and is used after it so as to obtain a truer surface on the piece of timber than is possible with the jack plane. It is also used for edging boards, and it is narrower than either the jack plane or the smoothing plane. Figs. 27, and 2S show two wood bottom smooth planes, one with a handle and one without, and Fig. 29 shows a smooth plane with an iron bottom.