The first operation in sharpening a saw is that of jointing the saw, Fig. 24. The purpose of this is to bring all teeth to an even length. This is done by drawing a flat file across the teeth of the saw. One or two strokes is usually sufficient. The file must be held perfectly square; this may be facilitated by use of a block called a saw jointer, as shown in Fig. 24.

The second operation in saw sharpening is that of setting the saw. This consists of bending the teeth outward, one on one side, the next on the other and so on till all the teeth are bent. The set should not extend more than half the length of the tooth. For ordinary work the teeth should be set about one-third the thickness of the blade. For dry lumber the saw will require less set than for green or wet lumber.

The third operation is that of filing the saw. In filing a cross-cut saw the point of the file should point toward the point of the saw at an angle of about 45 degrees. In filing a rip saw the file is held straight across the saw. File every tooth to a point, one-half of the filing being done from each side, being careful to stop filing a tooth when it has been brought to a point. File the entire length of the saw from one side, then reverse the saw and file from the other side. The front edge of each tooth projecting away from the filer and the back edge of the tooth next ahead, should be filed with the same stroke. Only forward strokes of the file should be used.

The fourth operation consists of placing the saw flat on a smooth surface, as the top of a bench, and running a whet-stone over the teeth so as to remove the burr from the teeth caused by filing.

Fig. 24. Jointing a Saw.

Fig. 24. Jointing a Saw.

Fig. 25. Filing a Saw.

Fig. 25. Filing a Saw.