CARPENTERS' TOOLS Steel Square. It is not only important that the workman should know the character and usefulness of the various materials, but it is also essential that he should be familiar with the steel square, which is the universal tool used to lay out the material. Figs. 16 and 17 show one side of one of the common squares in general use. The three parts are distinguished by special names, the tongue, the blade, and the heel. The longer and wider arm is the blade, the shorter and narrower arm is the tongue, and the point where the two arms meet is called the heel.
The numerous applications of the tool arc given in detail under the subject of "The Steel Square." Saws. Another very important and much used tool, wherever wood working is done, is the saw, and so much depends upon its careful manipulation and intelligent use that it will not be out of place to devote a few pages to a consideration of the different kinds of saws and their respective possibilities, as well as to their care and the way in which they should be chosen.
There are in general two kinds of saws, which differ from each other in the arrangement of the teeth, and which are intended, one for cutting wood in the direc tion of the grain, and the other for cutting wood at right angles to the grain. In order to cut the wood in the direction of the grain it is not necessary to cut through very many of the fibers, as the cut is, in general, parallel to them, but it is necessary rather to force the fibers apart without tearing them. Of course it is impossible to cut the wood without tearing the fibers to some extent, but this is the best way to make clear the difference in principle between the two kinds of saws, and an understanding of this difference is necessary in order to appreciate their construction and the proper care of them. The cutting of the wood across the grain, on the other hand, requires a tool made especially with a view to cutting through the fibers as quickly and as easily as possible. Besides these two there are various other special saws de signed for a particular kind of work, such as the cutting out of key holes, the cutting of dovetails, the cutting of miters, and other oper ations required in joiners' or carpenters' work.
Rip Saw. This saw is designed for cutting along the direction of the grain of the wood, and from this comes its name, which suggests very clearly its purpose. Fig. 18 shows one of these saws, but the shape of the blade varies a great deal with different makers, and some people prefer one shape while others prefer another.
The distinguishing feature is the shape and ar rangement of the teeth, which are shown in detail in Fig. 19. There are always a certain number of teeth to the inch length of the saw.
In this kind of a saw, the number is usually four or five, and it will be noticed that one side of the tooth is vertical while the other slopes. The vertical side of the tooth is always toward the front or point of the saw, while the sloping side is always toward the handle. The amount of slope to be given to the teeth of a saw is a matter of opinion and can be regulated when the saw is sharpened, or "filed," but the slope should always be a flat one in this kind of a saw, that is, it should make an angle of less than forty-five degrees with the horizontal, or with the line of the back of the saw.
It is held by some that the teeth of a rip saw should be straight on the front edge, that is, that they should have the edge at right angles with the side of the blade, while others maintain that the edge of the tooth should be cut across obliquely, so as to be at an angle of about eighty-five degrees with the side of the blade. A saw may be filed either way, according to.the opinion of the owner, the determining factor being usually the kind of wood to be cut and whether the grain is absolutely straight or more or less crooked. In the latter case the edges of the teeth should certainly have a slight bevel so as to give a cutting edge. The bevel should, however, be on alternate sides of adjacent teeth, that is, one tooth should be beveled toward the right and the next toward the left and so on. This arrangement helps to keep the saw straight while cutting, and prevents it from being forced over to one side or the other. Fig. 20 shows a view of the cutting edge of a rip saw, showing the way in which the teeth should be filed.