Notwithstanding the great diversity in the files alluded to in the foregoing section, it is to be remarked that all those hitherto noticed are made entirely of steel, and their teeth are all produced in the ordinary manner by means of the chisel and hand hammer; in the present section, a few of the less usual kinds of rasps, floats, and files, will be noticed, the teeth of which are, for the most part, produced by means differing from those already described.
The rifflers, fig. 815, used by sculptors, are required to be of numerous curvatures, to adapt them to the varying contour of works in marble. In general the rifflers are made of steel in the ordinary mode, but they have also been made of urrought-iron, and slightly case-hardened, in which case the points of the teeth become converted into steel, but the general bulk of the instrument remains in its original state as soft iron; consequently such case-hardened rifflers admit of being bent upon a block of lead with a leaden mallet, so that the artist is enabled to modify their curvatures as circumstances may require.
Several kinds of floats are made with coarse, shallow, and sharp teeth, which are in section like fig. 646, page 684; these teeth could not be cut with the chisel and hammer in the ordinary manner, but are made with a triangular file. Figs, a to l, 828, respresent the sections of several of these floats, which have teeth at the parts indicated by the double lines; for instance, a is the float, b the graille, c the found, d the carlet, e the topper, used by the horn and tortoiseshell comb-makers; parts of the names of which floats are corrupted from the French language, indeed the art was mainly derived from French artizans. The floats, f to i, are used by ivory carvers for the handles of knives, and in the preparation of works, the carving of which is to be completed by scorpers and gravers; k and l are used in inlaying tools in their handles; k is made of various widths, and is generally thin, long, and taper; l is more like a key-hole saw. When the teeth of these floats have been formed with the triangular file, and made quite sharp, the tools are first hardened and very slightly tempered, just sufficiently to avoid fracture in use; but, when after a period the tools have become dull, they are tempered to a deep orange, or a blue, so as to admit of being sharpened with a triangular file.
The larger of the floats, such as those a to e, used by the comb-makers, are kept in order principally by the aid of a burnisher, represented in two views in fig. 829, the blade is about 2 inches long, 1 inch wide, and 1/16 inch thick; the end is mostly used, and which is forcibly rubbed, first on the front edge of every tooth, as at a, fig. 830, and then on the back, as at b, by which means a slight burr is thrown up, on every tooth, somewhat like that on the joiner's scraper; but in this art the burnisher is commonly named a turn-file. When the teeth of the floats have become thickened from repeated burnishing, the triangular file is again resorted to, and then the burnisher for a further period; by these means the floats are made to last a considerable time.
The quannet is a float resembling fig. 819, but having coarse filed teeth, of the kind just described; it may be considered as the ordinary flat file of the horn and tortoiseshell comb-makers, and in using the quannet, the work is mostly laid upon the knee as a support. An ingenious artizan in this branch, Mr. Michael kelly, invented the quannct represented in figs. 830 and 831.
The stock consists of a piece of beech-wood, in which, at intervals of about one quarter of an inch, cuts inclined nearly 80 degrees with the face, arc made with a thin saw; every cut is filled with a piece of saw-plate. The edges of the plates and wood, are originally tiled into the regular float-like form, and the burnisher is subsequently resorted to as usual. The main advantage results from the small quantity of steel it is necessary to operate upon, when the instrument requires to be restored with the file. From this circumstance, and also from its less weight, the wooden quannet, fig. 830, is made of nearly twice the width of the steel instrument, fig. 819, and the face is slightly rounded, the teeth being sometimes inserted square across, as in a float, at other times inclined some 30 degrees, as in a single-cut file. A more elaborate, but less available, instrument was invented by Mr. White, probably during his residence in France, about the time of the Revolution (1793). It consisted of numerous parallel plates of steel, which were placed vertically and in contact, something like a pack of narrow cards, and were fixed in that position in an appropriate frame, and as the edges of the plates were all bevelled, they constituted a single-cut file. The most curious part of the contrivance was, the ingenious mode of chamfering the edges, as for this purpose the plates were loosened and arranged in a sloping direction, so that the chamfers then lay collectively in one plane, which was ground cither on a grind-stone, or a lead lap fed with emery; the plates were replaced perpendicularly before use. Means were also described for placing the steel plates square across the instrument as in a float, or iuclined to the right or left as in a file, according to the material to be wrought; and a drawing is also given of a circular float of similar nature for cutting dye-woods into small fragments. White's "perpetual" file, with moveable plates, is however scarcely known, and it is very questionable if it ever obtained more than the experimental application which led to its description having been published.*
The cutting of files by machinery is an operation that has engaged the attention of many persons, and the earliest attempt at the process that has come under the author's notice is that of Thiout aine, which was figured and described in a work by his son in 1740; and this machine being based on the manual process, in all probability differs but little in its general features from most of those of more recent projectors.