Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 95
SHARPENING HAND SAWS.
ОглавлениеThe teeth at both point and butt of a hand saw should be very slightly smaller than those in the middle, as it is at the last-named point where the greatest force is exerted in every down stroke. But it is absolutely necessary that the set is the same from point to butt of every saw, whether rip or cross-cut. The middle of the cutting edge of a cross-cut saw should be slightly rounded, being highest at about the middle. The saw being still in the saw vice, insert the file in a handle, and grasp it with the right hand, taking the point of file in the left, as shown in Fig. 287. Place the file against the face of that tooth nearest the handle that inclines away from the worker, holding the file at an angle with the blade of saw as shown in Fig. 287. Then lower the right hand to about the angle shown in Fig. 288 (which shows the left hand removed). The file should be held obliquely across the saw blade, as in Figs. 289 and 290, the point end of the file being inclined towards the saw handle as illustrated by Fig. 287. Gently push the file forwards, lifting it at the end of stroke, returning it, and again pushing it, until the point of the tooth has a keen edge. Repeat this upon each alternate tooth until all upon one side are sharpened. Afterwards turn the saw in its vice and sharpen the teeth upon the other side in the same manner. Be careful not to press the file against the back of the tooth, or unevenness will surely result. It may occasionally happen that when touched with the file, the saw may be found to be too hard. To soften it, remove the handle, and “blaze” by smearing the blade with a mixture of wax, suet, and oil, and heating over a fire till the mixture ignites. But this is not a method for the beginner, who would certainly spoil the saw. Keep all saws slightly rounding on the edge. The rip saw and hand saw can have a quarter of an inch rounding with advantage. To do this the points of the teeth must be frequently filed down, and the heel and the point filed away. There are always several teeth at the heel and at the point that do little work; those in the middle portion do most, and consequently wear away fastest. All saws, except circulars, have a constant tendency to get hollow, and this must be prevented; and the only way to prevent it is to file the teeth down by passing a partly-worn file along the edges, till it touches every tooth. Then, in filing the teeth, take care only just to take out this bright mark—not one touch more, or that tooth gets low and does not work; if some teeth are filed away even a little too much, the saw might just as well be that number of teeth fewer, as they do no work. A saw in thoroughly good order is so sharpened that each tooth does a share, and no one tooth more than the others.
Fig. 288.—Filing Saw Teeth.
Fig. 289.—Filing Saw Teeth.
Fig. 290.—Filing Saw Teeth.
Fig. 291.—Badly Sharpened Tenon Saw Teeth.