10. Saws.—Saws which are used in cutting across the grain are called crosscut; those which are used in cutting parallel to the grain are called rip-saws. Fig. 24. Upon the blade of a saw, near the handle, will be found a num ber.
This represents the number of points to the inch. Points should not be confused with teeth, for there is always one more point per inch than there are teeth.
To prevent the sides of a cut, or kerf, from binding the saw, the teeth are bent alternately from side to side, that the opening may be wider than the blade is thick. The saw teeth are then said to have "set." To do good work, a saw should have no more set than is necessary to allow free movement. Fig. 25. Damp, spongy lumber will require considerable set, while well-seasoned lumber necessitates but little.
The rake, or pitch of the teeth of a saw, is the degree of slant which the cutting edges possess with reference o an imaginary line passing thru the points of the teeth. Fig. 25. The amount of pitch given will depend upon the use to which the saw is to be put—whether for ripping or cross-cutting, and somewhat upon the hardness or softness of the wood to be cut.
Fig. 26 shows the saw in proper position. It should be held in the right hand with the left hand grasping the board, the thumb of the left hand acting as a guide in the beginning. The thumb should be held firmly on the board and the blade of the saw should be pressed lightly against it.
The cutting edge of the saw should be held at an angle of about forty-five degrees to the board and should be started on a backward stroke. The first few strokes should be short ones, increasing gradually in length. If the tool is sharp, but little pressure will ever be required and, in starting, the tool must be held up so that its weight shall come upon the wood gradually.
Saws can be guided better if the index finger of the right hand is allowed to extend along the side of the handle. Test occasionally, sighting down the saw blade to see that the sides of the saw are at right angles to the surface of the board. A try-square may be used by the beginner, as shown in Fig. 26.
If the saw does not follow the direction of the line, the blade should be slightly twisted, as the sawing proceeds, in the direction it ought to take. This must be carefully done so as not to cause the blade to bind and kink.
In sawing a board which has been fastened in the vise, the most convenient position is obtained by sawing at right angles to the surface. Unless the saw has considerable Fig. 27 set, difficulty will be experienced in changing the direction of the cutting should this be necessary. This may be overcome by lowering the handle so that the cutting edge shall make the same angle with the board as when the board rests on trestles.
When making a long cut, should the kerf bind, a wedge may be inserted as shown in Fig. 26.
All saws will work easier and will be found less likely to rust if their sides are rubbed occasionally with an oily rag or a piece of tallow.
12. The Crosscut Saw.—Fig. 25 shows the teeth of a crosscut saw. This saw is filed so that the cutting edges are on the sides of the teeth. Every tooth is sharpened to a point, one on the right side, the next on the left, giving two parallel lines of sharp points with a V-shaped groove between.
The pitch given the teeth of a crosscut saw will vary with the hardness or softness of the wood which is to be cut. For all-around use the amount of slant is about one-third of the whole tooth.
13. The Rip-saw.—The teeth of the rip-saw are chisel shaped, Fig. 28, and are made by filing straight across the blade. The front or cutting edges are filed so that they are Fig. 28square, or at ight angles to an imaginary line passing through the points of the teeth.
14. The Back-saw.—The back-saw, or tenon-saw as it is often called, has a thin blade strengthened by a heavy steel back piece. It is used upon work requiring delicate, accurate cutting. Fig. 30 shows the shape of the teeth, which differ slightly from those of the crosscut.
These teeth are suitable for both cross-cutting and fine ripping. But little set is given the teeth of the back-saw. In using this saw, Fig. 31, hold the work firmly against the stop of the benchhook with the left hand, guiding the saw with the forefinger or thumb placed against the blade just above the teeth. Hold the handle end of the saw highest. Begin at the farthest corner, using short, easy strokes.
Gradually lower the handle to a horizontal position, meanwhile
increasing the number of teeth used, but continuing thjs slow,
In accurate cutting, Fig. 32, where no paring or block-laning is to be done, the saw teeth should cut just by the line, with the kerf in the waste, but with no wood between the line and the kerf. To allow for paring or block-planing, saw about one-sixteenth of an inch in the waste. Fig. 33. When ripping, place the piece in the vise and begin sawing as indicated in Fig. 34. Place the saw so that just the whole of its thickness is in what is to become waste wood. Begin sawing as was done in cross-cutting. Gradually lower the handle, while sawing, until most is being cut from the side nearest you.
Fig. 35. Reverse the wood several times, working down one side then the other until the cross lines are reached. Fig. 36 illustrates the result of good and bad sawing.
15. The Turning Saw.—The turning or bow-saw is used for cutting along curved lines. Fig. 37 illustrates the manner of holding this saw. The sides of the blade must be held at right angles to the surface of the wood. Either or both handles may be turned, thus turning the blade with reference to the frame. Avoid turning the blade, however, as much as possible, and see that the blade is not twisted by turning one handle more than the other.
This saw may be used for cutting enclosed curves by boring a hole, releasing one end of the blade and inserting it thru this hole then replacing it in the saw frame.
As the cut of the turning saw is not very smooth, it is advisable to leave about one-sixteenth of an inch between the kerf and the line, to be removed later with the spoke-shave.
16. The Compass Saw.—The compas saw, Fig. 38, is better suited for inside curve sawing. Its use requires a steady hand, else the thin blade will buckle and break.
17. Saw Filing.—Learning to sharpen a saw is a difficult thing—so difficult that it is not considered within the province of a book on elementary woodworking to treat of it. One who uses saws, ought, however, to know the steps which are taken to put a saw in order.
The teeth are first set. Fig. 39 shows a common form o f s a w-s e t in position. Beginning at one end of the saw, tooth is bent outward by means of this instrument. The saw is then reversed and the remaining teeth are similarly treated.
As these saw-sets are adjustable, the teeth may be bent much or little as the work to be done demands.
Second, the teeth are jointed. A flat file is run lengthwise over them the full length of the saw so that none of the teeth may project more than others. Fig. 40 shows a flat file in position for jointing. This block keeps the surface of the file at right angles to the blade of the saw.
Third, the saws are filed, a three-cornered file being used for this purpose. The Lind of saw determines the angle or angles at which the file is held with reference to the saw blade.
Fig. 41 illustrates the position when filing the crosscut and Fig. 42 the rip-saw.
Fourth, the teeth are side jointed by laying the saw flat upon the bench and rubbing an oilstone over each side lightly, once. Fig. 43. This is to even the sides of the teeth that the kerf may be smoothly cut.