FILE MANUFACTURE. A file, as every one knows, is a steel instrument having fiat or curved surfaces so notched or serrated as to produce 1), series of fine teeth or cutting edges, which are employed for the abrasion of metal, ivory, wood, &fc.
Steel for making files, being required to be of unusual hardness, is more highly converted than for other purposes, and is sometimes said to be double converted. Small files are mostly made of cast steel. The very large files, called smiths' rubbers, are generally forged immediately from the converted bars. Smaller files are forged from bars which are wrought to the required form and size by the action of tilt-hammers, either from blistered bars or from ingots of cast atech These bars are cut into pieces suitable for making one file each, which are heated in a forge fire, and then wrought to the required shape on an anvil by two men, one of whom superintends the work, while the other acts as general assistant.
The next operation upon the blanks which are to be converted into files is that of soften ing or 'lightening,' to render the steel capable of being cut with the teething instruments. This is effected by a gradual heating and a gradual cooling. The surface is then rendered flat and smooth, either by filing or by grinding.
The cutting of the teeth is usually per formed by workmen sitting astride upon a board or saddle-shaped seat, in front of a bench, upon which is fixed a kind of small anvil. Laying the blank file across the anvil, the cutter secures it from moving by a strap which passes over each end and under his fest, like the stirrup of the shoemaker. He then takes in his left hand a very carefully ground chisel Made of the best steel, and in his right a peculiarly-shaped hammer. If the file be flat, or have one or more flat surfaces, the operator places the steel chisel upon it at a particular angle or inclination, and with one blow of the hammer cuts an indentation or furrow completely across its face from side to side, and then moves the chisel to the requi site positions for making other similar and parallel cuts. If it be a half round file, as a straight-edged chisel is still used, a number of small cuts are necessary to extend across the file from edge to edge. So minute are these cuts in some kinds of files, that in one specimen about ten inches long, flat on one side and round on the other, there are more than 20,000 cuts, each made with a separate blow of the hammer, and the cutting-tool being shifted after each blow. The range of manufactures afford few examples more striking of the peculiar manual tact acquired by long practice.
Several highly ingenious machines have been contrived for superseding the tedious operation of file-cutting by hand; but, suited as the process may appear to be for the use of machinery, it has been found to present such great difficulties, that we believe no file cutting engine has been brought successfully or extensively into operation. One very seri ous difficulty arises from the circumstance that, if one part of the file be either a little softer than the adjacent parts, or narrower, so as to present less resistance to the blow of the hammer, a machine would, owing to the per fect uniformity of its stroke, make a deeper cut there than elsewhere.
After the files have been cut, the steel is brought to a state of great hardness ; this is effected in various ways, according to the pur pose to which the file is to be applied : they are generally coated with a sort of temporary varnish, then heated in a stove, and then sud denly quenched. After hardening, the files are scoured, washed, dried, and tested.
We will here. give, from a Sheffield news ' paper, a description of a file intended for the Great Exhibition, the most elaborate perhaps ever produced. It was wholly made by a file forger named Hiram Younge, in the employ of Messrs. Carr of Sheffield. The length is 54 inches, breadth 31 inches, thickness 1 of an inch, weight 28 lbs. With some small ex ceptions, the whole surface is covered with ornamental designs, all cut by hand with hammer and chisel. The tangs (it is a double tanged file)—are sunk by filing, and are onnt ment,ed on one side with the national arms and the words "God save the Queen," on a shield; a front view of the cutlers' hall on the other, with the motto ' Pour parvenir a Bonne foy.' The other tang represents Atlas bearing the globe, with two lions conchant: beneath are the Sheffield arms, and a cornucopia on each side. On the reverse side appear the cutlers' arms with the emblem of industry— beehives and bees on the wing—on each side. On the moulding these words appear: Cut, designed, and executed by Hiram Younge, a member of the Sheffield file trade.' The centre or body of the file is ornamented on one side with an accurate, full-length view of the Great Palace of Industry, in perspective, forming an elegant and spirited sketch. The reverse side is occupied by a view of the Sheffield Infirmary ; while on the ends, be tween the centre and the tangs, are four views, illustrating the processes of file manufacturing. 1. A file-forger's shop, exhibiting bellows and other appointments, and a file-forger and striker in working costume. 2. The interior of a wheel : grinders at work. 3. A file cutting shop : three men cutting files, and one grinding his chisel. 1. A hardening shop : hardeners at work, and two women scouring files. The edges of the file are occupied with an inscription. The remaining space is filled up with chequered work, half diamonds, arc. This unique file revolves on pivots, so that every part can be inspected in succession with ease, and the position varied to bring out the innumerable effects which light produces. The lighter parts possess that peculiar bright richness observable on highly ornamented silver plate. But the most remarkable fea ture in this elaborate ornamentation is a number of trees in full foliage, luxuriant as the work of the pencil. Each separate shade is effected by a distinct style of perfect tooth. Those practised in the delicate art of file cutting can best appreciate this wonderful piece of work ; but the uninitiated may judge of its merit by bearing in mind that if a single tooth were cut too deep or too shallow, too narrow or too broad, or the least awry, it would destroy the uniformity of the shade, and that nowhere is there such a defect dis cernible.