Continuing this experiment, let us cut the fibers with a knife point in two parallel lines across the grain, close together, as at c. It will be found that the wood between these lines may now be easily removed with the narrow chisel. This fact is made the basis on which we construct the crosscut saw. Every tooth is sharpened to a point, one on the right side, the next on the left, giving two parallel lines of sharp points designed to cut the fibers, as was done in our experiment with the knife. [Fig. 12] shows the end view of the crosscut teeth enlarged. Observe that not only are the alternate teeth sharpened on opposite sides, but each tooth is bent outward from the body of the saw. This bending is called set, and is designed to make the saw cut, or kerf, wider than the thickness of the saw, that the latter may pass easily through the wood after the teeth have done their work. If it were not for this set, the fibers would spring back against the body of the saw after the teeth had passed and make the work very laborious. When a saw is properly set it should pass through the wood easily.
Fig. 12. Teeth of Crosscut Saw
Fig. 13. Teeth of Ripsaw
The teeth of the ripsaw are also set, but, as will be seen in the sketch, the bottoms are flat like a chisel instead of pointed like those of the crosscut teeth.
Beside the end views of the two kinds of teeth, the side views, which are also different, are shown in Figs. [12] and [13].
We are inclined to think of the saw as a very commonplace article, yet a careful examination will prove that the greatest care and skill are needed in its manufacture. Observe that the body, which must be of the best steel, tapers, being considerably wider at the handle than at the opposite end. This is to give strength, and to prevent buckling, or bending, as the tool is pushed forward.
Fig. 14. Body of Saw, showing Tapers