FILES, manufactory of Many useful tools have been invented for performing mechanical operations, which consist of a number of wedges or teeth, which may be conceived to stand upon, or rise out of, a flat or curved metallic surface. When these teeth are formed upon the edge of a plate, the instrument is called a saw ; but when they are formed upon a broad surface, it constitutes what is known by the name of a file. The comb-makers and others use a tool of this description, call ed a quonet, having coarse single teeth, to the number of about seven or eight in an inch. Fine tools of the same kind, name ly, with single teeth, are called floats. When the teeth are crossed, they are called files ; and when, instead of the notches standing in a right line, a num ber of single individual teeth are rais ed all over the surface, it is called a rasp. As the art of making files is nearly the same in its practice with regard to all the great variety of forms in which they are made, we shall confine our description to that•of the flat file.
Very little need be said in explanation of the method of forging these articles. They are usually made of steel, or more rarely of iron, case hardened. The forg ed files are brought to a flat surface on the grindstone, and are then ready for the file•cutter. This artist is provided with a great number of chissels, consisting each of a piece of steel of moderate thick ness, having a straight edge of greater length than the height of the chissel, the back of which terminates in a blunt angle or point in the middle of its length, upon which the blows are struck with a ham mer of about five or six pounds weight, for middling sized files, having its head all on one side of the stem, so as to re semble the capital letter L, in order that it may by its own weight naturally dispose itself with the face downwards. The file is placed upon a plate of lead on a small low anvil, close to which the workman sits, and on the left side of the block of the anvil are fastened the two ends of a leather strap, which he brings over the file, and by putting his right foot into the loop holds it steadily in its place. In this situatioq, taking the chissel between his left finger and thumb, he applies its edge across the file, where the cuts are to begin at the point, and gives it a blow ; the direction of the cut being inclined towards the tang, or that end of the file which is to go into the han dle. Immediately after this commenc
ing operation, he lifts the chisel, places its edge behind the other cut, and slides it forward till he feels it bear against the bur or protuberancy of the former cut, at which instant he gives the second blow ; a third is repeated in like manner, and by a continuance of the same proceeding, the whole surface at length becomes covered with single strokes or notches, each of which presents an ele vated sharp edge. The distance between stroke and stroke, or, which is the same thing, the coarseness of the file, depends entirely upon the violence of the blow, by which the bur is raised to a greater or less height ; but it isnot difficult with so weighty a hammer, after a very little prac tice, to give the strokes with great unifor mity of impulse, and to repeat them with such frequency, as to perform this appa renily delicate work with great speed and precision. The coarsest files have about ten or twelve cuts in the inch of length, and the very finest have upwards of two hundred.
As soon as the whole surface of the file has been thus cut, the workman files the bur off with a smooth file, so as to leave very little more of the stroke than what has entered below the original sur face; and then proceeds to give the se cond or cross-cut, forming an angle of about sixty degrees with the finest range of strokes. The intention to be answer ed by filing off the first edges is, to af ford a more even surface for cutting the second, which is done exactly in the same manner as the first range, and like wise to give a suitable figure to the small teeth or lozenge-shaped prominences, which stand up upon the face of the file after the cutting is completed. If this filing off were to be omitted, the teeth would be pointed and irregular ; whereas the useful and durable figure is that of a small rounded chisel or gouge.