FII.K MANUFACTURE. 



FILE MANUFACTURE. 



T6 



of tilt hammer*, cither from blistered ban or from ingota of 

 oast *tl. These bar* are out into piece* suitable for making one file 

 each, which are heated in a forge fire, and then wrought to too 

 required ahape on an anvil by two men : one of whom superintends the 

 work, and U nxponaible fur the goodneai of the file, while the other 

 acta aa general assistant. File* being of many different dupe* and 

 Jaw, aa square, triangular, flat, round, and half-round in their cnw 

 section, and parallel or tapering more or lea* toward* the end, and 

 ranging from the minute watchmaker'* file* of an inch or two in 

 length, to the ponderous rubber of two or three feet, there are of 

 coune many varieties in the forging process. The square and flat 

 file* are generally haped by the hammer only ; but for those of a 

 triangular or half-round section grooved bosse* or die* of the required 

 shape are attached to the anvil. Hound file* are made by mean* of 

 the instrument known to smith* a* a ttca^f, which may be compared 

 to a pair of such die*, one of which in inverted upon the oth. r to 

 receive the blows of the hammer. The projecting tang by which the 

 file is to be inserted in a wooden handle is formed at this time, and 

 the manufacturer'* mark is impressed with a steel punch. 



The next operation ia that of softening or annealing, to render the 

 steel capable of being cut with the toothing instrument*. The ordinary 

 mode of performing thin operation is to pile the steel blanks loosely 

 upon the bottom of a brick oven, and heat them with a fire kindled 

 beneath and around them, the heat being regulated by damp. T-. 

 \\ lifii the fire has been maintained sufficiently long, the pile is 

 smothered with ashes, every aperture by which air could enter the 

 oven U carefully cloned, and the whole is left to cool gradually. The 

 access of air during the heating tends to the oxidation of the steel, 

 and is consequently injurious : and on this account a more careful 

 method of annealing is sometimes adopted, by means of a ilo~.lv- 

 covered box filled with sand, into the midst of which the blanks are 

 plunged. 



After annealing, the surface of the metal must be rendered very 

 smooth anil cutting the teeth. This may l>e done either 



by drippiuy, or filing, first across, and aftervvanU along the surface; or 

 by grinding upon very large grindstones. The stripping process, 

 which is tedious and laborious, was formerly in common use, and is 

 still practised by some filemakers, especially in Lancashire, where 

 excellent files are manufactured; but the other is now the most 

 common method. 



The cutting of the teeth is usually performed by workmen MI t in;; 

 astride upon a board or saddle-shaped seat, in front of a well-lighted 

 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 feet, 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, the handle of which is fixed at such an angle that the 

 ojrtT.it or can, while making a blow, pull the hammer rather towards 

 him. If the file be flat, or have one or more flat surfaces, the operator 

 places the steel chisel upon it at a particular angle, and with one blow 

 of the hammer cuts an indentation or furrow, completely across its 

 face from side to side, but most commonly in on oblique direction ; 

 the metal displaced by this operation is not taken away, but is thrown 

 up in the form of a prominent angular ridge, with a sharp cutting 

 edge, on one side of the furrow. He then moves the chisel a little, 

 and by a second stroke cuts another precisely similar furrow parallel 

 to, and at a very short distance from, the first; and thus proceeds, 

 stroke by stroke, until the whole surface itt furrowed, beginning at the 

 point and ending at the tang-end. In the course of cutting, the file 

 i gradually moved from the operator by relaxing the pressure of the 

 strap from time to time. In this state, the file is said to be ti, 

 or liiujlt-foat ; and files so cut ore used for brass and the softer metals, 

 which are liable to clog a file of any other kind. For working ircn and 

 some other materials, double-cut, or crou-cut, files are used ; in which 

 the first row or series of cuts is crossed at on oblique angle by a 

 second ; the effect of which is to convert the surface into a collection 

 of very small angular teeth, admirably adapted for the abrasion of 

 hard substances. In making cross-cut files, a fine file is gently passed 

 over the first series of cuts or teeth to reduce the prominences to an 

 even surface before the second set is cut Files for wood ore usually 

 cut with a triangular pointed punch or chisel, instead of one with a 

 flat edge ; such files, as well as some of the deepest and coarsest cross- 

 cuts, are called ratpi. If the file be round or half-round, or have any 

 curved surface, it is still cut with the some kind of tool ; but as a 

 straight-edged cutting tool can only make a short indentation upon 

 ex surface, it is necessary to go round the file by degrees, 

 making several rows or ranges of minute cuts contiguous to one 

 



In addition to variation.! in the form and arrangement of the teeth 

 of files, their size varies extremely. The largest and coarsest smiths' 

 files are called rubbers ; and others, arranged in order of fineness, are 

 technically known as rough, bastard, second-cut, smooth, and dead- 

 smooth files, the latter producing so fine a surface when applied to 

 metal that the subsequent application of a burnisher U sufficient to 

 poliah it. 



In the art of file-cutting there are many points worthy of remark. 

 The angle at which the cuts are made depends greatly on the purpose 



to which the file is to be applied, and is made an especial object of the 

 cutter's attention. The cut, too, is not a mere indentation, mad 

 out reference to furm ; it is a triangular groove of particular sha 

 production of which requires a most discriminating tact in Uie manage- 

 ment both of the hammer and of the cutting-tool. Then, again, the 

 ir.dlcli.sm of the several cuts can only be brought about by 

 practised accuracy of hand and eye ; since there is no guide, gauge, or 

 other contrivance for regulating the distance. In a round file, too, the 

 several rows or cut* are brought side by side in such an exact manner 

 that it is difficult to conceive them to be formed singly and by hand. 

 It is possible, in a half-round file 10 inches long, to make 20,000 chisel- 

 cuts, each produced by a distinct blow from a hammer ; and files of 

 that length are actually made rijujlt-att, with 10,000 such indentations. 



The final process in the manufacture of files is the hardening of the 

 steel, a "process in which different manufacturers vary in practice. 

 There are differences, too, depending on the degree of hardness 

 required. In the ordinary process of hardening steel files three things 

 must be particularly observed : first, to cover the surface of the file ' 

 with some composition which, acting as a protecting varnish to it, may 

 guard it from oxidation and scaling when exposed to the .-!; M of the 

 fire, that the sharpness of the teeth may not be impaired, nor the sur- 

 face rendered rough, which would cause it to clog when in use; 

 secondly, to heat it very uniformly throughout to a red heat ; and, 

 thirdly, to cool it suddenly, by immersion in the freshest and coldest 

 water, in such a manner as to impart the greatest degree of hardness, and 

 to avoid the tendency to warping, which in long thin files is a difficult 

 matter. A mixture very commonly used for the first-mentioiitil pur- 

 pose consists of the grounds of malt liquor, or the cheapest kind of Hour, 

 yeast, and common salt. The use of the grounds is chiefly to enable the 

 files to retain a greater quantity of salt, which fuses, and form* a pro 

 touting varnish when in the fire. The heating is usually effected in an 

 i e of clean coke, the file, if small, being held by the tang t ml in 

 a pair of tongs, and frequently withdrawn, to see that no part becomes 

 over-heated. The proper temperature is indicated by a cherry-red 

 colour. A kind of oven is sometimes used for large files, to facilitate 

 the uniform application of heat, the oven being formed of fire-bricks, 

 open at one end to receive the files and fuel, anil the fire being urged 

 by bellows. Some file-makers put sulphuric acid or other substances 

 into the quenching-water, with a view to procuring the greatest possible 

 hardness. All files should be immersed quickly ; those of a flat, square, 

 triangular, or round form, being plunged perpendicularly into the 

 water; while the half-round, though kept perpendicular, should be 

 moved a little horizontally in the direction of the round side, to pre- 

 vent its becoming crooked. With every precaution the files are liable 

 to take some degree of warp or curvature in this process, to r. 

 which they are withdrawn from the water before they become quite 

 cold and straightened. Owing to their hardness, files are unavoidably 

 brittle, and they are t specially liable to break by the tang, owing to 

 their reduced substance ; to remedy which, some makers temper the 

 tang end by dipping it in a bath of melted lead. During the war of 

 the French revolution, the supply of English files being impeded, the 

 French file-makers were excited to great efforts to supply the defi- 

 ciency ; and these efforts are said to have resulted in the produe; 

 files of intense hardness, by dipping them into a composition of mutton 

 suet, hog's lord, and arsenic. 



After hardening, the files are scoured with a brush dipped in 

 mixed with a little sand or coke-dust; then thoroughly washed to 

 remove any saline particles which might tend to i : next 



dipped in water in which quick-lime has been dissolver 1. in order to 

 neutralise the effect of any which may yet remain ; ami finally dried 

 before the fire, brushed over with oil or a mixture of olive-oil and 

 turpentine, and wrapped up in oiled brown ; ilc. Before 



packing, files are sometimes tested by striking thorn gently on a piece 

 of hard steel, and also nibbing them gently from end to end. 



U IM n riles, otherwise of good quality, are reduced to a useless state 

 by wear, they are sometimes re-cut, the old teeth beitijj 

 removed by grinding. He-cut files are, of course, somewhat thinner than 

 when first nude, but in all other respects they may be equally good, if 

 the process is properly conducted. (I-.MIU t.. the superior quality of 

 the steel, worn-out files bear a comparatively high value as old metal, 

 and many are bought up for the purpose of converting them into 

 screw-drivers and gun-barrels. 



Several highly ingenious machines have been contrived foi 

 ceding the tedious operation of file-cutting by i uUxl as the 



process may appear to be for the use of iiiaehin.-iy, it has been found 

 to present such great difficulties that few file-cutting engines bav< 

 brought successfully or extensively Into operation. One very. 

 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 i 

 sent less resistance to the blow of the hamn him- would, 



owing to the perfect uniformity of its stroke, make a deeper cut there 

 than elsewhere ; whereas a workman who has been employed in the 

 trade from a boy can feel instantly when he arrives at any variation in 

 the quality or condition of the steel, and at once adapts the weight of 

 his blow to it. The application of machinery to the toothing of 

 extremely fine-faced files seems conceivable however, because in such 

 the fft or direction of the teeth is a matter of much less importance 

 than perfect equality of surface. The double dead-cut files of the 



