Extracts From "HANDBOOK FOR LUMBERMEN," Henry Disston & Sons.
Fig. 13 is a representation of some of the saws we have seen; there are entirely too many such now in use, and we have no doubt their owners are shortening their lives in the use of them as well as those of the saws. To owners of such saws we say, take them to the factory and have them retoothed, or buy a new saw and take a fresh start, and steer clear of this style of filing.
As we said in the preceding pages, and as will be seen by Figs. 10, 11 and 12, the filing should be done from the heel of saw toward the point. Many practical saw filers contend this is wrong, that the filing should be done from point of saw toward the handle, but the only support they have for their theory is that they do away with the feather edge that the filing from the heel of saw puts on the cutting face of tooth. The feather edge is no objection, as the main part of it is removed when the teeth are side-dressed after filing, as we direct in our summary of saw filing on Against the correctness of filing from point to handle may be cited the following objections: -
Where a different angle of back is required (it being remembered that angle of face should be the same in nearly all cross-cut hand saws, and that angle of back governs angle of point), it will be found very difficult to obtain it without changing angle of face of tooth, and as the cutting duty is on the long side of face, any change is of course of great influence. Again, (though we think the above argument sufficient) to file from point of saw, it is necessary to file with the teeth bent towards the operator; this will cause the saw to vibrate or chatter, which not only renders good, clean, even filing impossible, but breaks the teeth off the file.
In the preceding illustrations, we have only given the coarser saws that are in most general use, but the same principle of filing should be applied to the finer toothed saws regarding angles and pitch suitable for woods of different degrees of hardness, the only actual difference being that one saw has finer points, and they being finer, require a little more care and delicate touch in setting and filing.
Fig. 13 is a section of an eleven-point saw suitable for the finer kinds of work on dry, soft woods, such as cutting mitres, dove-tailing, pattern work etc.
Fig. 15 shows a section of saw with same number of points of Fig. 14, but filed same as Fig. 12. This saw is for finer work, same as Fig. 14 only on the medium hard woods. Fig. 16 is a still finer saw for fine work on the very hardest woods having same dress as Fig. 14.
Fig. 17 is the finest tooth saw of its kind that is made for wood. All the above mentioned saws in Figs. 14, 15, 16 and 17, are made especially hard and will not admit of setting, but being made thinner at the back, when properly filed, will cut clean and sweet. Teeth such as shown in Fig. 17 are used principally on back saws and smooth cutting hand-saws. To maintain the original shape of these teeth use a cant safe back file.
Fig. 18 is a section of a pruning saw which differs from a cross-cut hand saw in being thicker, having a little more pitch to the teeth and being ground thinner on the back in proportion to its width. These of course, are made for cross-cutting only, as there is not as great a variety in the work, nor as much difference in the woods to be sawed as to degrees of hardness, being used only as a pruning saw on fruit and shade trees, which are always practically green and comparatively soft. The "nib" near the end of a hand saw has no practical use whatever, it merely serves to break the straight line of the back of blade and is an ornamentation only.
These saws are for miscellaneous sawing. The best form of tooth for this purpose is the same as Fig. 18, excepting that it has a trifle less bevel. As the nature of the work partakes about as much of cross-cutting as of ripping, and as a cross-cut saw will rip better than a rip will cross-cut, it is apparent the shape of tooth should be between the two. These saws are all ground, filed and set in the same manner. Scroll and web saws are ground, filed and set in the same manner, and should have pitch according to the work to be done. If more ripping than cross-cutting is done
as in large felloes, more pitch is given than in compass saws and vice versa, though these saws are almost universally run with a rip-saw tooth and have very little variation in the pitch.
These saws are for cutting metal, such as brass, iron or untempered steel, and should have a little finer tooth than the average butcher saw. They are so hard that none but the best superfine files will sharpen them. Like the butcher saws, filing must be done straight through and no bevel.
This is an important part of the work of keeping in order and should always be done after the teeth are jointed and before filing. In all cases the set should be perfectly uniform, as the good working of the saw depends as much on this as on the filing. Whether the saw is fine or coarse, the depth of set should not go, at the most, lower than half the length of the tooth, as it is certain to spring the body of saw if not break the tooth out. Soft, wet woods require more set as well as coarser teeth than dry, hard woods. For fine work on dry woods, either hard or soft, it is best to have a saw that is ground so thin on the back that it requires no set; such saws are made hard and will not stand setting, and an attempt to do so would surely break the teeth out.