Sharping

“ MACHINE FOR SHARPENING SAWS.--E. B. Rich, South Boston, Mass.--This invention relates to a machine for the sharpening of saw blades, whether straight or circular, and consists in the combination of a revolving or rotating grinding wheel made of any suitable material, and a holder for the saw blade, so arranged together that as the grinding wheel revolves the saw will be presented to the same, or the wheel to the saw-blade, in such a manner as to produce the desired sharpening of the teeth, in regular order and succession. ”

“ As the student must in any case learn how to sharpen his tools, it will be just as well to get them in that way rather than ready for use. As this process of sharpening tools is a very important one, it must be reserved for another place. Should tools be seriously blunted or broken they must be reground. This can be done by the carver, either on a grindstone or a piece of gritty York stone, care being taken to repeat the original bevel; or they may be sent to a tool [41] shop where they are in the habit of grinding carving tools. ”

“ Section knives, during the process of sharpening, are subjected to three distinct processes: 1, Grinding; 2, Honing; 3, Stropping.
Grinding is one of the most important, though it is probable that it will rarely be undertaken by the microscopist himself. More knives and razors are spoiled in grinding than in any other way. We have now in our possession an excellent knife, which in an evil hour we entrusted to a New York cutler, and received it back utterly ruined, the temper being entirely taken out of the blades! ”

“ And as the contrast of the effect of the same tool under different circumstances in the same substance is considerable, great also is likely to be the contrast between the edges of the tools and the manner of using them, e. g., the axe, which is the proper tool in the direction of the fibre, is operated upon by impact, while a saw, which is the proper tool across the fibre, is operated upon by tension or thrust, but never by impact. ”

“ When we pass from the tool and its contrived handle to the mode of using, and the purpose for which it has been constructed, we find, as a rule, a cutting-edge formed by two inclined surfaces meeting at an angle, the bisecting line of which passes through the middle of the metal. It is very apparent that the more acute this angle is, the greater, under the same impact, will be the penetrative power of the axe into the material against which it is driven. ”

“ Some persons prefer to turn the knife over, drawing it first from the left hand and then toward it, sharpening each surface alternately on the same edge of the steel. This is more difficult to do, as you cannot so surely keep the blade at the same angle,—and this is the most important point. If held at any other than the proper angle, either no edge is made, or it is taken off as soon as obtained. ”

“ Some spent all their money for knives owning as high as five or six at one time. Their interest centres in the number and sharpness of the blades. Each boy's knife must be sharper than those of others, and comparison of knives with respect to sharpness is common. The blades are tested by cutting into hard material, by seeing which can cut the largest shavings or chips from wood, or by trying to cut paper or a hair. ”

“ A carving tool is sharpened from both sides because the edge, so made, enables the artist to cut from many positions without turning the wood, and when he can use both hands he has the same advantage to a greater degree. ”

“ After so much careful work, it does seem as if not one pen out of a thousand could be faulty; but every one has to be carefully examined to make sure that the cutting, piercing, marking, forming, tempering, grinding, and slitting, are just what they should be. ”

“ We have dwelt at length upon this point because so much has been written comparing the edge of a razor to that of a saw, that some persons actually advise us to give the edges of our knives and razors a saw-like character, under the impression that by so doing they will work better. This is a fallacy; the best work will be obtained from the smoothest and most perfect edge, provided the latter is thin enough. ”

“ There are some which occupy an intermediate position between those ground at the edge only, and those which are polished all over; inasmuch as not only has their edge been sharpened by grinding, but the principal asperities both of the sides and faces have been removed in a similar manner, yet without polishing anything like the entire surface. ”

“ Carving in the round is cutting an object which is finished on every side, as a bust or statue. It is in fact “statuary.” It seems to be very difficult work to a beginner, but the pupil who has mastered the rudiments which are laid down in this book, and who can measure and cut a low relief of an inch, or a high relief pattern of two or three inches, will find no trouble whatever in carving something small in the round, and in progressing from this to something larger. ”

“ He grasps your hair; he holds a sharp carving knife in the other hand; you reach out for the knife and seize it, when, with a terrible oath, he draws the keen blade out of your grasp, and almost severs your fingers in doing so! ”

“ The above-quoted description, though short and superficial, is sufficient to indicate some of the chief difficulties of the swordsmith’s art, and it sets one thinking, too, as to the various uses to which cutting instruments are put, and gradations of hardness, from the high temper of razors and certain chisels to the low temper of hunters’ and sailors’ knives, which should always be of rather soft steel, for they are sharpened more easily, and the saw-like edge is better suited for cutting flesh, ropes, etc., than a very fine edge would be. ”

“ I always carry a pocket carborundum stone, and I carefully clean and sharpen my knife every time I use it. Before using the stone it is important to see that there is no blood or blubber remaining on the blade. After a heavy day’s flensing it may take from half an hour to an hour to bring the edge to perfection again, and I am always amused at the man who brings something resembling a butcher’s steel and says: “You might just sharpen that for me, will you?” ”

“ Saw filing.— (A.) This is an accomplishment which every young wood-worker should master, as its possession will save expense and inconvenience, and add much to his efficiency as a workman.
(B.) The first step in sharpening a saw is to examine the edge carefully to see if the teeth are of an even length; if they are not, they should be jointed. This is done by using a flat file held perfectly square in a block, as shown in Fig. 89. One or two light strokes usually will be enough to make all the teeth of the same length. ”

“ Every blade which man could mould, Which could cut, or slash, or cleave, or rip, Or pierce, or thrust, or carve, or strip, Or gash, or chop, or puncture, or tear, Or slice, or hack, they all were there. ”

“ A knife is a broad, sharp nail projected; the saw is a set of nails, or perhaps teeth; and the primitive hatchet was a finger-nail and looks very like a talon, as did its maker's finger. The fist is a hammer. ”

“ If the savage chips his flints with a blow of the right, he holds the core, or main mass of stone from which he strikes it, firmly with his left. If one hand is specially devoted to the knife, the other grasps the fork to make up for it. ”

“ Fig. 27.
The sharpening of bits of a form other than that of the chisel is done by means of “swages.” The tempering is effected in the way already described [34] in reference to hand drills. As in the latter case, the degree of temper must be suited to the hardness of the rocks to be penetrated. Generally the straw colour will be found to be the best degree. It is a remarkable fact that the wear of the cutting edge of a machine drill is, for a given length of boring, five or six times less than that of a hand drill. Steel of the best quality should always be used. ”

“ Another reason is, that a blade thus shaped can be sharpened very easily, when it becomes blunt. Nothing is needed but to take a flint, or even the back of a common knife, and scrape it along the edge, and, if properly done, a single such scrape will sharpen the weapon afresh. The head is always made of soft iron, and so yields easily to the sharpening process. The reader may remember that the harpoons which we use for whale hunting are always made of the softest iron ”

“ If you merely rub the blade of a knife rapidly on a piece of wood it will become hot enough to burn your hand.
Percussion is merely a more energetic kind of friction, and is often resorted to by the blacksmith to light his furnace. He places a nail or other piece of soft iron on his anvil, and beats it rapidly with the hammer, when it becomes actually red hot. ”

“ When a saw becomes worn, and its teeth require sharpening, the first thing to do is to joint it, that is to say, bring down all its teeth to the same height, which may be done by holding an emery block or file against it while the saw is running, care being taken to hold the block or file firmly, and to continue the process until the tops of the teeth run true. ”

“ In sharpening a knife-blade on an oilstone care should be taken to keep the blade nearly flat on the stone in order to get a thin, sharp edge. The knife should be sharpened first on one side and then on the other, until the desired edge is obtained. ”

“ When the pieces of bone, ivory, pearl, tortoise-shell, horn, or other substances, which are to form the outer surface of the handle, are roughly cut to shape; when the blade has been forged and ground, and when the steel for the spring is procured, the whole are placed in the hand of a workman, who proceeds to build up a clasp-knife from the little fragments placed at his disposal. ”

“ Every edge, when closely examined by a microscope, presents a more or less saw-like and jagged appearance. It [Pg 23] is merely a question of degree, and, in a sword to be used for ordinary cutting and thrusting, you want to secure hardness sufficient to produce a good edge and an instant return to its former shape after any reasonable bending, and you want to avoid anything like brittleness or liability to snap. ”

“ Among some hundreds of scrapers, principally from the Yorkshire Wolds, I have met with between twenty and thirty which show decided marks of being worn away along the circular edge, by friction. In some, the edge is only worn away sufficiently to remove all keenness or asperity, and to make it feel smooth to the touch, and this perhaps along one part only of the arc. In others, the whole edge is completely rounded, and many of the small facets by which it was originally surrounded, entirely effaced. ”

“ The Grindstone.—As most of the tools require a grindstone for sharpening purposes, an illustration is given as a guide, with a diagram to show the proper grinding angle. In Fig. 16 the upright [Pg 23] (A) of the frame serves as a line for the eye, so that if the point of the tool is brought to the sight line, and the tool (C) held level, you will always be able to maintain the correct angle. ”

“ In some instances the broken part of one instrument has been converted into another form—as, for example, a fragment of a broken sword into a knife or dagger, or a palstave that has lost its cutting end, into a hammer. ”

“ The housewife’s best method of sharpening or rather keeping the edges straight and keenly cutting is the steel. When the knife really gets dull it should be ground. The use of the stone or carborundum by the ordinary operator often wears the steel. However, if the use of the grinder or the stone or the carborundum is really known, time and money will be saved in the sharpening process. Sharp knives save temper, save food to a great degree, and therefore if you can’t sharpen knives yourself send them out to be taken care of once or twice a year. ”

“ STILL keeping to the Cutting Tools and their varieties, we come to the Saw, i.e. the cutting tool set with teeth upon its edge. Now, in plain fact, there is no cutting instrument that does not more or less partake of the character of the Saw; for, in the first place, it is absolutely impossible for man to grind an edge so fine that, when magnified, it will not appear to be deeply notched, and, in the next place, its cutting powers are greatly due to the notches and teeth, and the direction of their points. ”

“ The small striæ, resulting from the friction which has rounded the edge, are at right angles to the flat face of the implement, and the whole edge presents the appearance of having been worn away by scraping some comparatively soft substance—such, for instance, as leather. ”

“ They take a flat piece of wood, that is pretty soft, and make a small dent in one side of it; then they take another hard round stick, about the bigness of one's little finger, and sharpening it at one end like a pencil, they put that sharp end in the hole or dent of the flat soft juice, and then rubbing or twirling the hard piece between the palms of their hands, they drill the soft piece till it smokes, and at last takes fire. ”

“ The angles of the bevels of a gouge are similar to those of a chisel. In sharpening, hold the tool at right angles to the edge of the stone, instead of parallel as with the chisel. Move it lengthwise of the stone, at the same time [63] rotating the handle so as to give the blade a circular motion as from A to B, Fig. ”

“ The artist took up from the table the poniard with the red stain on its blade, and proceeded to sharpen the edge on a square slab of marble that did duty occasionally as a palette. Silly that I was! I actually believed that my bold manner had frightened him, and that he was going to comply with my request. The noise produced by the sharpening process was not a pleasant one, and it set my teeth on edge.
"Oh, that'll do!" I cried impatiently—that is, impatiently for a captive, dependent on the pleasure of [Pg 255] another for his release. "That'll do. It's sharp enough for the purpose." ”