MANUFACTURE. FOrMerly, all files were hand made, the steel bar being forged to shape, ground smooth, and mit by hand tools. Most tiles are now made by machinery designed to perform all of these essential operations. The old method of hand cutting has a peculiar interest because of the deftness and skill required of the workman, and it will be described briefly for this reason, and also because it will help to explain the na ture of the work required of modern file-cutting machinery. The following description is taken from Holzapffel's Turning and Mechanical Ma nipulation: "The first cut is made at the point of the file; the chisel is held in the hand at a horizontal angle of about 55° with the central line of the file. . . . and with a vertical inclination of about 12° to 14° from the perpendicular. . . . The blow' of the hammer upon the chisel causes the latter to indent and slightly to drive forward the steel, thereby throwing up a trifling ridge or bur; the chisel is immediately replaced on the blank and slid from the operator, until it encounters the ridge previously thrown up, which arrests the chisel or prevents it from slipping farther back, and thereby determines the succeeding position of the chisel. The heavier the blow. the greater the ridge, and the greater the distance from the pre ceding cut at which the chisel is arrested. The chisel, having been placed in its second position, is again struck with the hammer, which is made to give the blows as neatly as possible of uni form strength ; and the process is repeated with considerable rapidity and regularity, 60 to SO cuts being made in one minute, until the entire length of the tile has been cut with inclined. parallel, and equidistant ridges, which are col lectively denominated the first course. So far as this one face is concerned. the file, if intended to be single cut, would lie then ready for hardening. Most files, however, are double cut; that is, they have two series or courses of chisel cuts. In cutting the second course, the chisel is inclined vertically as before, at about 12°, but its edge only a few degrees from the transverse line of the file, or about 5° to 10° from the rectangle.
The blows are now given a little less strongly, so as barely to penetrate to the bottom of the first cuts, and from the blows being lighter they throw up smaller burs, consequently the second course of cuts is somewhat finer than the first. The two series, or courses, fill the surface of the file with teeth, which are inclined toward the point of the file." At first sight it would appear from the sim plicity and continual repetition of the movements required in file-cutting that it was an operation especially adapted to be performed by machinery. Nevertheless. it was not until many years after the first inventor of a file-cutting machine had patented his device that tile-cutting machines were successfully used, and that machine-cut tiles could compete with the handmade product in market. Among the notable inventors of tile-cut ting machines may be Hien thnled (1699) ; Eardonet (1725) ; Thiont (1740) ; Itra (-hal and Gamin I I 765-7s; ; Raoul I I soo) ; Ericsson 11830 ; Robinson t1S4:1) ; and Winton (1817). one of these machines was com mercially successful. In however, Sir.
W. T. ....ii•holson of Providence, It. I., in vented zi tile-cnt t Mg machine, which, as improved and modified from time to time, is now extensively used in the United States. .thout the same time M. liernot, a French man, devised a machine which proved com mercially successful. Brielly described, the sue cessful forms of tile-cutting machines consist of a moving table on whieli the tile-blank is fixed, and which moves it, progressively under it sort of trip-hanuner arrangement earrying cutting chisels. In making machine-made files the bars of steel are first forged by hand or by machines, and then graund smooth. The smoothed blank is then run through the cutting machine. The final process is to temper and harden the out file.