FILBERT. See HAZEL.
FILE (Fr. file, a row, Lat. fluor, Itgl. fito), in a military sense, is used to signify any line of men standing directly behind each other, as rank refers to men standing beside one another. In ordinary formations of the present day, a battalion stands two deep, or in two ranks—front and rear—wherefore a file consists of two men. Some times, however, the battalion may be formed much more solidly, as in a square, when the file comprises a far larger number. The number of files in a company describes its width, as the number of ranks does its depth. thus, 100 men in "fours deep" would be spoken of as 25 files in 4 ranks.
A file is a steel tool, having its surface covered with teeth or serra tures, and used for cutting down and shaping metals and other bard substances. There is little doubt that in the earlier stages of metal-working. when bronze implements first superseded those of stone, rough stones were used for the purposes to which files are now applied; nevertheless, the use of files dates from high antiquity. They are mentioned in the Old Testament in the first book of Samuel, xiii. 21, also in the Odyssey.
Files are made of almost every conceivable shape, to suit the very varied purposes to which they are applied—flat, square, round or rat-tail, triangular, half-round, feather edged, etc., besides being variously bent, in order to get at intricate work. Nearly all these files are made thicker in the middle, or " bellied," the object of which will be explained under FILING.
Files require to be made'of the very best steel, which is first forged into the required shape, and is then called a "blank." The blanks are then finished more accurately to the required form by grinding, planing, or filing.
The blanks thus prepared and well softened (see TEMPERING) are next handed to the cutter, who sits astride on a low bench or stool, and has before him a stone anvil, with a flat piece of pewter laid upon it. The blank is held upon the anvil, with its tang towards the cutter, by means of a long loop of leather-strap, into which the cutter places his foot. He then cuts the teeth by striking with a hammer a short stout chisel, held obliquely at an angle of about 12° or 14° from the perpendicular. The object of
this will be easily understood; for, if the chisel were perpendicular, a furrow like the letter V would be indented, and an equal burr struck up on each side; but, instead of this, a cutting tooth like that of a saw, but with less obliquity, is required; this is effected by the obliquity of the chisel, and a burr is thrown up on one side only—viz., towards the tang.
The astonishing regularity observable in the distance between the teeth is secured in this way: The cutting is commenced at the point of the file; the chisel is then drawn backwards, laid upon the blank, and slid forwards till it reaches the burr raised by the last cut; the blow is now struck, and another tooth and burr produced, which serves as a guide for the next cut; and so on. The distance between the teeth thus depends on the force of the blow, and the obliquity of the cut; for the heavier the blow, the greater the ridge or burr, and the obliquity determines the distance of the cut from the burr; the skill of the workman consists, therefore, in the precise regulation of the blows.
Most files are double cut—that is, they have two series of courses of chisel-cuts, which are oppositely inclined at an angle of about 55' to the central line of the file. The second course is made in the same manner as the first, but with lighter blows, and is usually somewhat finer than the first. This angular crossing converts the ridges into pointed teeth. Files used for soft metals which are liable to clog the teeth, are single cut—that is, they have but one course of cuts. Taper files have the teeth finer towards the point. Rasps for wood are cut with pointed chisels; each tooth being an angular pit with a strong burr, instead of a long furrow. The newly cut teeth in the soft steel are preserved from injury by being laid upon the softer pewter block before referred to. The rapidity with which the blows are struck varies with the fineness of the file; 60 or 80 cuts are commonly made per minute.