The next process is that of cutting the files, which is performed by means of a chisel and hammer on an anvil. The chisel and hammer are of such a size as the size and cut of the file require. The file-cutter is also provided with a leather strap, which goes over each end of the file, and passes round his feet, which are introduced into the strap on each side, in the same manner as stirrups are used. He therefore sits as if he were on horseback, holding his chisel with one hand, and his hammer in the other, at the same time he secures the file in its place by the pressure of his feet in the stirrups. While the point of the file is cutting, the strap passes over one part of the file only, while the point rests upon the anvil, and the tang upon a prop on the other side of the strap.

File 446

When one side of the file is single cut, a fine file is ran slightly over the teeth to take away the roughness, when they are to be double cut; and another set are then cut, crossing the former nearly at right angles. The file is now finished on one side, and it is evident that the cut side cannot be laid upon the bare anvil to cut the other. A flat piece of an alloy of lead and tin is therefore interposed between the serrated surface and the anvil, while the other side is cut, which completely preserves the side previously cut. Rasps are cut in precisely the same way, using a triangular punch instead of a flat chisel. The art in cutting a rasp is to place every new tooth opposite to a vacant space in the adjoining row of teeth. The last and most important part of file-making is the hardening them. In effecting this, three things are to be observed: 1st. To prepare the file on the surface, so as to prevent it from being oxidated by the atmosphere when the file is red hot, which effect would not only take off the sharpness of the tooth, but render the whole surface so rough that the file would, in a little time, become clogged with the substance it had to work upon.

This is accomplished by laying a substance on the surface consisting of salt dissolved in water, and stiffened with ale grounds or common flour. When it fuses, this forms a kind of varnish, which defends the metal from the action of the air. 2d. The heat ought to be very uniformly red throughout, and the water in which it is quenched fresh and cold, for the purpose of giving it the proper degree of hardness. And lastly, the manner of immersion is of great importance to prevent the files from warping, which, in long thin files, is very difficult. After the file is properly heated for the purpose of hardening, it should be cooled as soon as possible. The most common method of effecting this is by quenching it in the coldest water. All files, except the half-round, should be immersed perpendicularly, as slowly as possible, so that the upper part shall not cool. This management prevents the file from warping. The half-round file must be quenched in the same steady manner, but at the same time that it is kept perpendicular to the surface of the water, it must be moved a little horizontally in the direction of the round side, otherwise it will become crooked backwards.

When the files are hardened, they are brushed with water and coke dust, the surface becoming of a whitish grey colour, as perfectly free from oxidation as before it was heated. They may likewise be dipped in limewater, and dried before the fire as rapidly as possible; after which they should be rubbed over with olive oil, in which is mixed a little turpentine, and then they are finished. To preserve them for use, or pack them for sale, they are wrapped in stout oiled brown paper in half-dozens, the paper interposed between each preventing any injury to the opposed teeth.

The operation of simple file cutting seems to be of such easy performance, that it has for almost two centuries been a sort of desideratum to construct a machine to perform that which is not only done with great facility by the hand, but with wonderful expedition. It is said, that a lad not very experienced in the business, will produce with his hammer and chisel nearly three hundred teeth in a minute. With respect to machinery, Mathurin Jousse, in a work entitled, La Fidelle Ouverture de l'Art de Serrurier, published at La Flesche, in Anjou, in 1627, gives a drawing and description of one in which the file is drawn along by shifts by means of wheel-work, and the blow is given by a hammer. There are several machines for this purpose in the Machines approuvees par I'Academie Royale de Paris. There is also one published in the second volume of the Transactions of the American Philosophical Society; and a patent was taken out by Mr. William Nicholson, in 1802, for the same object. From the knowledge, talent, and assiduity, of the last-mentioned inventor, we may be assured that it was a very elaborate and judiciously-constructed machine; nevertheless it was found wanting, and never got into practical operation; files, therefore, continue to be cut as they were a century ago.

File-cutting is an art that appears, at first thought, extremely simple, but a little investigation of the subject will convince the reader, (as it did ourselves many years ago, when we designed a machine for the purpose,) that it abounds with difficulties, which, though probably not of an insuperable nature, are such as call for unremitting study, the devotion of much time, and the incurring of a considerable expense to accomplish. No man, therefore, should undertake it who is not possessed of abundant capital, leisure, and constructive skill. In the operations of filing, the coarser cut files are always to be succeeded by the finer, and the general rule is to lean heavy on the file in thrusting it forward, because the teeth of the file are made to cut forwards; but in drawing the file back again to make a second stroke, it is to be lifted just above the work, to prevent its cutting or rubbing as it comes back. The rough file, or a rubber, serves to take off the most uneven part of the work; then follows the bustard file, to reduce the file cuts or scores of the rough file, and next usually a smooth file, to remove the scores of the bastard, and prepare the work for the burnisher, if it is to be polished.