The common file, as every workman knows, is an implement, the flat or curved surfaces of which are notched or serrated in such a manner that, being rubbed on the wood, ivory, metal, or other hard substance for which the tool is intended, a surface of more or less smoothness is obtained.

Files are made of bars of steel prepared in a peculiar manner, it being necessary that the file should be formed of the hardest possible metal, or else its working surface would be speedily worn away.

The steel is therefore rendered harder than usual by means of a process known as double conversion; the metal thus prepared being said to be doubly converted. Small files are generally made of cast-steel, which is for this purpose preferred to forged steel, on account of its fineness and quality. The larger kind of files are forged from bars of steel, which have been beaten into the requisite shape by means of the tilt-hammer. The largest kind of flies, rather formidable looking tools, are forged from the barsteel, without the latter undergoing the preliminary process of tilt-hammering.

The files are then shaped the square and flat ones by means of a common anvil and hammer; those of a circular, half-round, or triangular form by means of bosses or dies, made of the corresponding shapes, fitting into grooves made for them in the anvil.

The surface of the file thus prepared is perfectly smooth, but it has to undergo another process that of softening before it can be serrated or toothed. This softening, or lightening, as it is technically called, is effected by placing a number of blanks, as the uncut files are termed, in a large brick oven, made perfectly air-tight, to prevent the steel from becoming oxidized.

The fire is made to play round the oven until the blanks are perfectly red-hot, when the heat is relaxed, and the oven gradually allowed to cool. On the perfection of this process depends much of the value of the file, and the labor of the worker. If the metal be too soft, the indentations may be too heavy and irregular if it be too hard, the workman will find much of his labor fruitlessly expended.

After being softened, the blanks are carefully ground and smoothed down to the requisite shape, after which they are passed to the file-cutters.

File-cutting is a curious and interesting process. The cutting-rooms are generally long, low apartments, with as many windows as possible, it being essential that the workman should have plenty of light, so as to immediately detect or prevent any flaw in the cutting. The work-benches are placed along the wall, just below the windows, each file-cutter sitting upon a stool, or astride a saddle-shaped seat, immediately in front of the bench.

Before each workman is small anvil fastened to the bench in such a way that it can be instantly removed if required. The cutter ties one of the blank files upon the anvil, securing it from slipping by means of a strap which passes over the ends of the file, and which is held tightly in its place by the weight of his foot. He then takes a peculiarly shaped hammer and a short chisel, rather broad in appearance, having a carefully ground edge, and formed of extremely hard steel.