CARE OF SAWS, AND EQUIPMENT.
Elementary woodwork can be more readily learned from small pieces of wood than from large; so the exercises that are here given are of such dimensions that they can be easily handled in working out the problems.
Since it is by what we study and learn that we are able to do something else, the student in beginning this work should thoroughly familiarize himself with the tools, their names and uses, so that he may more readily understand their application in the work that follows.
The equipment for the general use of students in each bench locker is as follows:
| 1 | 20-inch Rip-Saw. |
| 1 | 20-inch Cross-Cut Saw. |
| 1 | 10-inch Back-Saw. |
| 1 | 8-inch Try-Square. |
| 1 | 8-inch Bevel. |
| 1 | 8-inch Wing Dividers. |
| 1 | Marking Knife. |
| 1 | ⅜-inch Hand Mortising Chisel. |
| 1 | Bit Brace. |
| 1 | ¼-inch, ⅜-inch, ½-inch and ¾-inch Auger Bit. |
| 1 | Nail Set. |
| 1 | Mallet. |
| 1 | Hammer. |
| 1 | Oil Stone. |
| 1 | Oil Can. |
| 1 | Screw Driver. |
| 1 | Dust Brush. |
The equipment of tools in drawer and under the care of individual students is as follows:
| 1 | Number 5 Bailey Iron Plane (Jack-Plane). |
| 1 | Number 4 Bailey Iron Plane (Smooth-Plane). |
| 1 | Marking Gauge. |
| 1 | ¼-inch, ½-inch, ¾-inch, and 1-inch Bevel Edge Paring Chisel. |
| 1 | ¼-inch and ¾-inch Skew Turning Chisel. |
| 1 | ¼-inch and ¾-inch Turning Gouge. |
Tools, such as molding, beading, rabbeting, and plow planes are found in the tool room, and are issued to students on check when required.
Fig. 1.
[Fig. 1] shows the double bench equipped with rack, cam and quick acting vises, with the locker for the general tools and four drawers on each side of the bench with tools for the use of the individual student. Carpenters’ benches are usually about 33 inches high, while cabinet and pattern makers’ benches are from 2 inches to 4 inches higher.
The careful workman as a rule takes great pride in the condition in which his bench is kept; so the beginner should see that his immediate surroundings are kept in a neat, workmanlike manner, and with everything in proper place.
Care should be taken to protect the top of the bench from injury; it should never be marked by the chisel or cut by the saw. If chiseling has to be done on the bench, place the work on the bench hook or on a board, and in sawing use a bench hook such as is shown in [Fig. 2], that has a side lip that will protect the bench top.
Fig. 2.
The bench hook is made by students as an exercise, and is used to replace those hooks that have become worn out.
The material, which is delivered from the lumber yard in boards or planks, has to be cut up into lengths and widths suitable for the work to be done. The tools used for doing this cutting are the rip-saw and the cross-cut saw.
Now, a great amount of time can be lost in this work by the student, for the reason of his trying to do work with one tool when another should be used, and especially is this so in regard to saws. A saw will cut faster than a chisel in some places, and sometimes make the work as good if not better; so the student should learn to file and to keep a saw in just as good order as any other tool used.
We devote considerable space here to the saw, for we feel that the saw as one of the principal tools is often neglected, and is not used by students in their work as much as it should be. By a judicious use of this tool much time can be saved and a greater amount of ground covered than by trying to use a chisel or a jack knife in its stead.
Saws are either reciprocating or continuous in action; the first being a flat blade and a practically straight edge, making a plane cut, as in mill, jig, and sash saws; the latter either a circular or rotating disc, cutting in a plane at right angles to its axis (see buzz-saw in shop) or a continuous ribbon or band running on two pulleys, making a plane or curved cut with a straight edge parallel to their axis of rotation (see band-saw in shop).
Practically speaking, the teeth are a series of knives set on a circular or straight line, each tooth cutting out its proportion of wood, and kept from cutting more by the teeth on either side of it. Each tooth should cut the same amount and carry out the chips or dust, dropping it to the side or below the material being sawed. Different kinds of woods require teeth different in number, angle or pitch, and style of filing.
The perfect saw is one that cuts the fastest and smoothest with the least expenditure of power; to do this it is evident that each tooth should be so constructed and dressed as to do an equal proportion of the work, for if any of the teeth are out of line or shape they are not only useless themselves but a disadvantage to the others.
A saw tooth has two functions—paring and scraping. A slitting or rip saw for wood should have its cutting edge at about right angles to the fibre of the wood, severing it in one place, the throat of the tooth wedging out the piece.
Fig. 3.
The rip-saw, [Fig. 3], should be filed square across, and the front or rake of tooth should be at about right angles to the edge of the saw.
After jointing and setting, file one half the teeth from each side, which will give to the cutting edge of the tooth the slight bevel it should have for soft wood; for medium hard woods use a finer toothed saw, and file in the same manner; for the very hard, tough and cross-grained woods, use a saw still finer with the teeth filed slightly beveling, as ripping cross-grained stuff partakes a little of the nature of cross-cutting.
In all cases where ripping is done, the thrust of a saw should be on an angle of about 45 degrees to the material being cut, as shown in [Fig. 4]. This makes a shearing cut, an advantage that can be quickly demonstrated with an ordinary pocket knife, cutting any piece of soft wood.
Saws are designated by the number of points or teeth per inch, and the selection of a saw depends upon the character of wood to be worked. A rip-saw should have from 4 to 10 teeth per inch, the cross-cut saw from 6 to 16 teeth per inch. This includes the back-saw, it being filed the same as a regular cross-cut saw.
Fig. 4.
Fig. 5.
The harder the wood, the greater the number of teeth the saw should have.
We will now consider the cross-cut saw tooth in regard to rake or pitch; this being one of the most important features, too much care cannot be taken to have the correct amount of pitch for the duty required. To illustrate this. [Fig. 5] represents a board, across which we wish to make a deep mark or score with the point of a knife. Suppose we hold the knife nearly perpendicular as at B; it is evident that it will push harder and will not cut as smoothly as if it were inclined forward as at A. It follows then that the cutting edge of a cross-cut saw should incline forward as at [C, Fig. 6], rather than stand perpendicular as at [D, Fig. 7].
Fig. 6.
Fig. 7.
Too much hook or pitch and too heavy a set are very common faults, not only detrimental to good work but ruinous to the saw; in the first case, by having a large amount of pitch, the saw takes hold so keenly that frequently it “hangs up” suddenly in the thrust—the result, a kinked or broken blade; in the second, by having too much set, the strain caused by the additional and unnecessary amount of set is out of proportion to the strength of the blade, and it is broken in the same manner. The most general value of pitch used is 60 degrees, though this may be varied a little, more or less, to advantage, as occasion may demand.
In all cases the size of tooth depends largely upon the duty required; a long tooth has the demerit of being weak and liable to spring, but the merit of giving a greater clearance to the saw-dust. The throat space in front of each tooth must be large enough to contain the dust of that tooth from one stroke; the greater the feed the deeper the dust chamber required, or the more teeth. Where the teeth are fine the shape of the throat is of special interest.
The teeth of a hand-saw should be filed so true that on holding it up to the eye and looking along its edge, it will show a central groove down which a fine needle will slide freely the entire length. This groove must be angular in shape and equal on each side, or the saw is not filed properly and will not run true.
Fig. 8.
Fig. 9.
Fig. 10.
Fig. 11.
[Fig. 8] shows how the groove should appear on looking down the edge of the saw. The action should be such that the bottom of the cut or kerf will present the appearance as shown in [Fig. 9], and not as in [Fig. 10]; the cutting action is shown in [Fig. 11], the cutting being done with the outside of the tooth; the fibre of the wood is severed in two places, and the wood is crumbled out from point to point by the thrust of the saw.
The proper amount of bevel is very important, as is demonstrated by the [above figures], for if too much bevel is given the points will score so deeply that the fibres severed from the main body will not crumble out as severed but will be removed by continued rasping. This is true, particularly in hard woods, as they require less bevel, as well as pitch, than soft wood.
The next point to be considered is the bevel or fleam of the point. In [Fig. 12] the filer, as in all cases, files from the heel to the point; which is the only correct way.
Fig. 12.
The file is supposed to be perpendicular to the side of the saw in the vertical plane ([see Fig. 13]), at an angle of about 45 degrees in the horizontal plane, measuring from file line towards heel ([see Fig. 14]).
Fig. 13.
[Fig. 15] is a fair representation of many saws that we have seen owned by workmen; the result of owning such tools is shown in the poor work turned out by them.
Fig. 14.
As has already been said, the filing should be done from the heel of the saw toward the point. Many practical saw filers contend that this is wrong; that the filing should be done from the point of the saw toward the handle; but the only support they offer for this theory is that they do away with the feather edge that the filing from the heel of saws puts on the cutting face of the tooth. The feather edge is no objection, as the main part of it is removed when the teeth are side-dressed after the saw is set and sharpened.
Against the correctness of filing from point to handle may be cited the following objections:
Where a different angle of back is required (it should be remembered that 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 the angle of face of the tooth, and as the cutting duty is on the long side of the face, any change is, of course, of great influence. Again, to file from the point of the saw it is necessary to file with the teeth bent toward the operator. This will cause the saw to vibrate or chatter, a thing which not only renders good, clean, even filing impossible, but breaks the teeth off the file.
Fig. 15.
The setting of a saw is an important part of the work in keeping a saw in order, and should be done AFTER the saw has been jointed, and before filing.
The set should be uniform throughout, as the good working of a saw depends nearly as much on this as on the filing. One great mistake is often made in setting a saw, and that is that many try to put the set in the blade instead of in the tooth. The set should not go at the most lower than half the length of the tooth; by going lower it is liable to spring the body of the saw, if not break the tooth out.
Two methods may be given for setting saws. The first, or old method (employed before saw-sets were invented, and still used by old mechanics) is to take a hardwood block, lay the saw on it, and with a nail set and hammer set every other tooth on the side, then turn the blade over and repeat the operation on the teeth missed from the first side. It is needless to make any comment on this method when saw sets can be bought that are absolutely reliable in their operation.
The second method is to use the saw-set. Saw-sets are made in many styles, and can be bought at any hardware store.
Fig. 16.
Fig. 17.
Figs. [16] and [17] show two styles of saw-sets; much might be said in favor of each.
Saw clamps or vises used to hold the saw when filing can be bought (see [Fig. 18]), but a simple homemade vise can be put together by means of two pieces of board, one 3 feet 6 inches long and 6 inches wide, and one 2 feet 4 inches long and 6 inches wide. By fastening a piece 2½ inches thick about 10 inches from the top of each, to act as a fulcrum, and fastening a piece on each board at the top to act as jaws, and using a wedge at the bottom to tighten it up, a very serviceable vise is obtained ([see Fig. 19]).
Fig. 18.
Fig. 19.
To assist those not skilled in the art of filing, there is made a saw-filing clamp with a guide, of which a cut is here shown in [Fig. 20].
A few general rules may be observed in saw-filing: See that the file is held at the same angle throughout the operation. File every other tooth on one side, and when filed, reverse the saw and file the other teeth from the other side. For rip saws, place the file at right angles with the saw, and file the rake of tooth at right angles to the edge. After a saw is properly set and filed, lay it on a flat board and rub over the points of the teeth on the sides with an oil stone; this will regulate the set and insure smooth cutting, making the filing last longer. Should the saw not run true take another cut with the oil stone over the side toward which it leads.
Fig. 20.
A fast cutting cross-cut saw should have deep teeth.
Much useful information on saws can be obtained from a small book published and issued by Disston & Sons, Philadelphia, entitled “Hand Book for Lumbermen,” which, I believe, can be obtained on application.
The other tools used in this course will be taken up in order as they are used in the work.