The crosscut saw really severs or cuts the fibers of the wood twice, as shown at a in Fig. 12, the intervening projections being loosened and carried out as dust by the thrust of the saw, producing a nearly straight-bottomed kerf, as shown at 6. A crosscut saw for ordinary work should have 5 or 6 points to the inch; but for fine work 10 or 12 points would be better, especially for dry woods, either soft or hard. A section of a 6-point crosscut saw is shown in Fig. 13, and one of a 13 1/2-point in Fig. 14.
We find that while the rake or tooth bevel in rip saws is all on the back of the tooth, the rake in crosscut saws is on the side of the tooth, as shown at a, Fig. 13. In ripping, the point of the tooth acts as a chisel, cutting off the fibers of the wood, each tooth chiseling off a shaving as it passes through the board; but in crosscutting, the side of the tooth does the cutting, and therefore must have its bevel on the side.
Fig. 11. Position in Ripping.
Fig. 12. Kerl Made by Crosscut.
In Fig. 13 the fleam - angle of the tooth with the plane of the saw blade - is about 45 degrees, and, as shown, there is no hook or pitch, the vertical angles being the same both front and back of the tooth. This form of tooth works well in wet or in very soft wood; but for wood that is well seasoned, and for all the harder woods, the pitch, or vertical angle or inclination, of the front of the tooth should be about 60 degrees to the tooth edge of the blade, as shown at b, Fig. 15. The amount of pitch in the teeth of a saw may be varied for different purposes or for different woods, but should be such as to loosen and carry out the intervening wood. Otherwise this would have to be rasped or filed out by the continued action of the saw.
The fleam or horizontal angle of the side of the crosscut saw tooth is very important. When filing, the file should be held horizontally and at an angle of about 45 degrees to the side of the saw, lengthwise of the blade, as illustrated in Fig. 15, and each alternate tooth must be filed from the opposite side of the blade, beginning at the heel and filing toward the point of the saw.
The objection is often raised by saw filers, that, in filing from the handle end of the saw toward the point, a feather edge is made by the file and turned backward on the point of the tooth. The first thrust of the saw through the board, however, will remove this featheredge entirely; whereas, if the filing is done from the point of the saw toward the handle, it is necessary to file the teeth bent toward the operator, which causes the saw to vibrate, or chatter, and this not only renders good even filing impossible, but breaks the teeth of the file.
Fig. 13. Crosscut Saw Teeth.
Fig. 14. Crosscut Teeth for Fine Work.
Fig. 15. Filing Crosscut Teeth.
For hand and back saws, a saw set that acts on the principle of the hammer and anvil, such as the one illustrated in Fig. 16, is best. The spring sets, so much in use, will not give so regular and even a set to the teeth as will one or more light blows with the hammer on the beveled face of the anvil. By this method the tooth is not bent or sprung beyond the position in which it is intended to remain, and the blade of the saw is not bent or affected by the stroke of the hammer on the point of the tooth. A saw set, of the kind shown in Fig. 16, can be adjusted to set the points of the teeth to any depth desired; and, even if repeated light blows are given, the tooth cannot be bent beyond the required distance. The blow may be struck on a with a light mallet or it may be struck from below with the operator's foot on a treadle connected with e, leaving both hands free to hold and to guide the saw.
In setting a saw, it is always better to use two or three light blows on a tooth than to try to do the work with one heavy blow; and this is especially the case if the saw is hard, as all good and well-tempered saws should be.