Hand saws are of two kinds - rip and crosscut. The former, as the name indicates, is for cutting with the grain, or lengthwise of the board to be sawed. In Fig. 10 is illustrated a rip saw having 5½ points to the inch, which will work rapidly and with ease in pine and other soft woods. If mahogany, cherry, or other hard wood is to be ripped, a six-point saw should be used. Kip saws should be filed with all the bevel on the back of the tooth, as shown at b in Fig. 10, the front or "throat" of the tooth being at right angles to, or "square" with, the tooth edge of the blade, as at a in the same figure. The position of the line cd, whether perpendicular or slanting, is called the "hook" or "pitch" of the tooth.
Rip saws should be filed square across; that is, the file should be held horizontal and at right angles to the side of the blade, always filing each alternate tooth from the opposite side of the saw; this, if done by beginning at the heel and working the file toward the point of the blade, will give a very slight bevel to the back edge of the tooth, causing it to cut cleaner and with less set than if filed otherwise.
Rip saws require very little set for use in dry, well-seasoned lumber, such as is always used in pattern making. The teeth should be "set," or bent, only at the points, as shown at e and f in Fig. 10; and in no case should the set exceed more than half the depth of the tooth.
When the points only are set, the saw will work more freely, and the blade of the saw will not be "sprung," or bent, in setting In using a rip saw, the front or cutting edge of the saw blade should be held at an angle of about 45° to the board, as shown in Fig. 11. This brings the back of the tooth nearly at right angles to the fibres of the wood, and insures a shearing cut. For fine work and well-seasoned material, hand saws may be bought ground so thin on the back as to require no set. Such tools work very smoothly and easily, cutting away less wood and doing better work than saws that have been set.
The crosscut saw really severe or cuts the fibres of the wood twice, as shown at a in Fig. 12, the intervening projections being loosened dust by the thrust of the saw, as shown at b (Fig. 12).
A crosscut saw for ordinary work should have five or six points to the inch; but for fine work ten or twelve 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 an 13½-point in Fig. 14.
In considering rip saws we find that the rake or bevel is all on the back of the tooth. In crosscut saws the rake 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.
In Fig. 13 the bevel or fleam of the tooth is about 45°, and, as shown, there is no hook or pitch, the angle being the same on both the 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 and firmer woods, the pitch of the front of the tooth should be at an angle of about 60° to the tooth edge of the blade, as shown in Fig. 15, and at b in Fig. 16. The amount of pitch in the teeth of a saw may be varied as demanded for different purposes or for different woods, but in all cases 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 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° to the side of the saw, lengthwise of the blade, as illustrated in Fig. 16; 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 feather edge entirely; whereas, if the filing be 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. 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. 17, 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 illustrated in Fig. 17 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.
TRIPLE DRUM SANDER. J, A. FAy AND Egan Co.
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.
The back saw illustrated in Fig. 18 is used as a bench saw for light or fine work, and for fitting and dovetailing. Saws of this type are made from 8 to 14 inches in length, the 10- and 12-inch being convenient sizes for general work. As the metal back holds and stiffens! the saw, a thin blade should always be selected; and the methods of filing, jointing and setting are the same as already described for hand saws. At least two back saws will be found necessary, one filed for crosscntting, and the other filed as a rip saw for cutting with the grain of the wood, as in the cutting of tenons and dovetails.
While for those who have had experience in carpentry the following exercise in the use of the back saw may not be necessary, it is recommended to all beginners who wish to acquire skill in the use of this important tool.
Take any block of wood from 12 inches to 16 inches long, about 2 inches wide, and about 1¾ inches in thickness. With try-square and a sharp-pointed pocketknife, lay it out as illustrated in Fig. 19, on the upper, front, and back sides of the block. The knife-cuts must be at least 1/32 inch deep, and about ¼ inch distant from each other. Next proceed to saw up the block into thin sections, sawing each time so that the saw kerf will be just outside of, but close to the knife line, as indicated at a.
The saw-cut through the block should be true to each of the three lines; and while the saw passes along one side of the line, its teeth should not scratch the opposite side of the knife-cut, but should leave a smooth, clean angle of the knife-cut on the block, as shown at b in Fig. 19, while at the same time it should be so close to the line as to leave no wood to be smoothed off with plane or chisel.
A few hours' thorough and careful practice of this exercise will enable any one to use the saw successfully.