A saw tooth has two functions—paring and scraping. A slitting or rip saw for wood should have its cutting edge at about right angles to the fibre of the wood, severing it in one place, the throat of the tooth wedging out the piece.
Fig. 3.
The rip-saw, [Fig. 3], should be filed square across, and the front or rake of tooth should be at about right angles to the edge of the saw.
After jointing and setting, file one half the teeth from each side, which will give to the cutting edge of the tooth the slight bevel it should have for soft wood; for medium hard woods use a finer toothed saw, and file in the same manner; for the very hard, tough and cross-grained woods, use a saw still finer with the teeth filed slightly beveling, as ripping cross-grained stuff partakes a little of the nature of cross-cutting.
In all cases where ripping is done, the thrust of a saw should be on an angle of about 45 degrees to the material being cut, as shown in [Fig. 4]. This makes a shearing cut, an advantage that can be quickly demonstrated with an ordinary pocket knife, cutting any piece of soft wood.
Saws are designated by the number of points or teeth per inch, and the selection of a saw depends upon the character of wood to be worked. A rip-saw should have from 4 to 10 teeth per inch, the cross-cut saw from 6 to 16 teeth per inch. This includes the back-saw, it being filed the same as a regular cross-cut saw.
Fig. 4.
Fig. 5.