shoulder, or in filing out rectangular corners, have one or more of their edges left uncut, or safe as they are called; such safe-edges rubbing against the work and guiding the cut part of the file, without acting on the part which they rub. In some cases the edges alone are cut, and the sides left safe or smooth..

With respect to the forms of files, their sections are derived from the square, the circle, and the equilateral triangle, as shown in the following figures.

Fig. 905. The names of some files are derived from their sections, as square, round, and half-round files; others from the uses to which they are applied, as saw-files, slitting, warding, and cotter files. But the files in most common use are those known as taper files, hand files, cotter and pillar files, half-round, triangular, cross and round files, square, equalling, knife and slitting files, and rubbers.

SECTIONS DERIVED FROM THE triangle.

Taper files or taper-flat files vary in length from about 4 to 24 inches: they are rectangular in section, as in No. 2; they are considerably rounded on their edges, and somewhat also in their thickness; hence they are said to be bellied: all four varieties of cutting are applied to these files, which are in general use among smiths and mechanics.

Hand files or flat files resemble those last described, except that they are nearly parallel in width and less taper in thickness. They are commonly used for flat surfaces, and when more accuracy is required than in the work operated on by taper files; but in filing narrow apertures and notches, the taper file is used, first with the small end; next, the central and wider part; and then the whole length of the tool.

Cotter files vary from 6 to 22 inches in length: they are used in filing grooves for the cotters, keys or wedges, used in fixing wheels on their shafts; whence the name. They are narrower than hand files, and nearly flat on the sides and edges, so as to present almost the same section at every part of their length. Taper cotter files or entering files differ from the

VOL. I.

above: they taper in width and thickness, but have very little swell.

Pillar files, Section No. 3, are much narrower and somewhat thinner than hand files, and are used for lighter work, or for completing work that was begun with the hand file. They have usually one safe edge, and vary from 3 to 10 inches in length.

Half-round files, Section No. 11, are not, as the name would imply, semicircular in section, but the curvature may in general vary from the fourth to the twelfth part of the circle, the former being called full half-round, and the latter flat half-round files. Halfround files are usually taper: they vary from about 2 to 18 inches in length: the convex surface is used for various kinds of hollowed work, and the flat side for general purposes.

Triangular files, Section No. 17, also called threesquare files, vary from 2 to 16 inches long: they are used for internal angles, for clearing out square corners and for sharpening saws.

Cross files, crossing files, or double half-rounds, Section No. 12, are circular on both faces, but of two different curvatures. They are used for filing out the crosses or arms of small wheels as in clock-work, the opposite sides of the tool presenting a choice of curvature.

Round files, No. 9, vary from 2 to 18 inches in length; they are usually taper, and are used for enlarging round holes: when small and taper they are termed rat-tail files, from the resemblance to a rat's tail; when small and parallel they are called joint files, from their use in filing the hollows in the joints of snuff-boxes, &c.

Square files vary from 2 to 18 inches long: they are mostly taper, and in some cases have one safe edge; they are used for small apertures, and for purposes to which the ordinary flat files are inapplicable on account of their larger size.

Equalling files, Section No. 4, are usually parallel in width and always parallel in thickness: they range from 2 to 10 inches long. In locksmiths' ward-files the two broad surfaces are left safe.

Knife files, Section 19, are usually made very acute on the edge, and from 2 to 7 inches long, both parallel and taper; they are used in cutting narrow notches, and in making the entry for saws and for files with broader edges; also in bevilling or chamfering the sides of narrow grooves.

Slitting files or feather-edged files are similar to the last, except that they have two thin edges instead of one, as in Section 20.

Rubbers are strong heavy files made of inferior steel from 12 to 18 inches in length, and from 3 to 2 inches on each side: they are convex or fish-bellied, and are frequently designated by their weight, which may vary from 4lbs. to 15 lbs. Their section is square and triangular, as in Nos. 1 and 17; or with one side rounded, such as would be formed by the union of Nos. 2 and 10, in which case they are termed halfthick. Their chief use is to brighten the surface of the work.

The small files used in watch-making are numerous.

TT

In the following enumeration of the Sections Nos. 1 to 24, the names of watch-makers' files are marked in italics.

Section No. 1. Square files, parallel and taper, some of which have one safe side: also square rubbers.

No. 2. Cotter files when large; verge and pivot files when small.

No. 3. Hand files, parallel and flat files: when small, pottance files; when narrow, pillar files; also taper flat files.

No. 4. When parallel, equalling, clock-pinion, and endless-screw files; when taper, slitting, entering, warding, and barrel-hole files.

Nos. 5 and 6. French-pivot and shouldering files, which are small and stout, and have safe-edges: when made large, and right and left, they are called parallel V-files, from their use in making the hollow V Vs of machinery.

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spanners for hexagonal and octagonal nuts, or six or eight canted bolts and nuts, as they are called.

No. 19. When parallel, flat dovetail, banking and watch-pinion files; when taper, knife-edge files. When the wide edge is round and safe, moulding files and clock-pinion files.

No. 20. Screw-head files, feather-edged files, clock and watch-slitting files.

No. 21. Used in finishing small grooves and keyways: it is also named a valve file from one of its applications.

No. 22. A compound of the triangular and halfround file: similar files are sometimes made with three rounded faces.

No. 23. Double or checkering files, used by cutlers, gun-makers, and others. These files are similar in their application to the double saws used for cutting the teeth of racks and combs. [See COMB, Fig. 605,

No. 7. Flat file with hollow edges, used as a nail page 419.] file for the dressing case.

No. 8. Pointing mill-saw file, round-edge equalling file, and round-edge joint file; made parallel and taper.

No. 9. Round file, gulleting saw file; parallel and taper.

No. 10. Frame saw file for gullet teeth. No. 11. Half-round file: nicking and piercing files; cabinet floats and rasps; all usually taper. Round-off files for rounding or pointing the teeth of wheels. These files have a pivot at the end opposite the tang.

No. 12. Cross files and double half-rounds. No. 13. Oval files; oval gulleting files for large saws. Ocal-dial file when small. No. 14. Balance-wheel or swing-wheel files, the convex side cut, the angular sides safe.

No. 15. Swaged files for finishing brass mouldings. No. 16. Sir John Robison's curvilinear file. The inventor states that, having found a difficulty in filing hollow surfaces, in consequence of the scratches which the irregular cutting of even the best half-round or round files leave in the work, it became a question whether the teeth of these files could not be made as perfect as in flat files, by cutting flat strips of rolled steel plate on one side, and then squeezing them into the desired curve by a screw-press and a block-tin or type-metal swage, and, in the case of a round file, by pressing the plate round a cylindrical mandrel. In testing this proposal, Messrs. Johnson and Cammel took a thin equalling file, cut on both faces, such as No. 3 or 4, softened and bent it and then re-hardened it, thereby producing a file with a convex and a concave surface, as in No. 16. With a plate of equal thickness the central part was found to bend more easily than the edges, thus making the curve irregular; but by making the blank thinner and more flexible at the edges, the bending was successful and the section became truly circular. These curved files are now regularly manufactured.

No. 17. Triangular, three-square, saw files, and rubbers cut on all the sides.

No. 24. Double file formed by fixing two flat files together in a wooden stock, and used for filing blacklead pencils to a fine conical point. It was invented by Mr. Cooper under the name of the "Styloxynon."

In the manufacture of files, the steel must be of good quality and highly converted; for if too soft or unequal in texture, the file itself would soon be worn down instead of the surface upon which it is intended to operate; if, on the contrary, it be too hard, the teeth become brittle and chip off at every stroke. Smith's rubbers are forged square from the bars of blistered steel as they leave the converting furnace; smaller files are forged from bars or rods of various shapes and sizes, tilted or rolled as nearly as possible to the sections required. Files of the best quality are made from cast steel. The iron bearing the mark CCND makes excellent steel for files; but the finest clock and watch-makers' files are made from the hoop L or Dannemora iron.

In forging files coke is used as the fuel. The general arrangements for forging are similar to those described in the article CUTLERY, p. 480. The man called the striker, is furnished with a large doublehanded hammer with a broad face at either end; but

the hammer wielded by the maker is smaller and single

No. 18. Cant file used for filing the insides of handed, somewhat conical in shape, the wider end

forming the face. Three-square and half-round files are forged in grooved bosses or dies fixed in the anvil. The rod of steel being raised to the proper heat, which ought not to exceed a blood-red, the end is hammered until it fills the die: the maker holds the die and strikes with the small hammer; the striker standing before the anvil deals powerful blows on the heated metal, the flat faces of the hammers covering a considerable portion of the surface of the blank file at each stroke, expanding and levelling it at one operation. When the blank has been forged to the proper length, the tang is also drawn out by cutting into the blank a little on both sides with a chisel, so as to form in many cases sharp square shoulders, and then drawing out the part so cut to form the tang. The maker's mark or monogram is then stamped on. Blanks for round files are formed in a slightly conical swage: blanks for flat and square files are formed by hammering. The maker accustoms himself, as much as possible, to the forging of one description of file, in order that by the concentration of his skill and attention on one article he may attain perfection in its manufacture.

The forged blanks are carefully annealed, or lighted, in order to make the metal soft enough for cutting the teeth. Blanks for common files are softened in an ordinary annealing oven, but the best blanks are protected from the action of the air by being buried in sand contained in an iron box: this is slowly raised to the proper heat, which, as in the forging, ought not to exceed a blood red.

to allow the mass of metal to be pulled towards the workman while making the blow. The chisels are formed of good tough steel, and also vary with the size of the file: they are somewhat broader than the file to be cut, and are sharpened to the proper angle: they are only just long enough to be held between the fingers and thumb somewhat as a pen is held, only in the left hand, the hollow of the hand being turned to the workman. But the peculiar method of handling the chisel depends in great measure on the kind of tooth to be cut. The file is held to its place on the anvil by means of a leather strap passing over each end of the file, and then under the feet of the workman in the manner of stirrups. At every blow of the hammer the chisel is made to cut a tooth, and the blows follow each other in rapid succession, the workman after every blow advancing the chisel forward by so slight a movement as to be scarcely perceptible. The chisel forms a number of angular grooves parallel to each other, the tooth being formed by the metal left between every two grooves. The skilful workman adjusts the weight of his blow to the kind of metal he is operating upon; and even in the same file, if one part be softer than another, he adapts the weight of his blow so that the teeth may be of the same size in every part. As the work proceeds he gradually shifts the file forward by loosening his tread upon the straps. When one surface is covered with single cuts, he proceeds, in double-cut files, to add a second row of teeth, making them cross the first at a certain angle, for which purpose the chisel requires to be held in a particular manner. When one side is covered, he proceeds in like manner to fill a second side; but as the teeth just finished would be injured by placing them on the naked anvil while hammering, they are protected by interposing a flat piece of an alloy of lead and tin, which comLiterature and Education, appointed by the Society for Promoting pletely preserves the side already formed. Similar I pieces of alloy with angular and rounded grooves are

The surfaces of the blanks are next made accurate in form and clean in surface by stripping or grinding. The former process consists in smoothing the surface of the blank with a hard file, first across and then lengthways: this is the method adopted in Warrington, where most of the files manufactured are small. In Sheffield, all the blanks above a certain magnitude are ground on large grindstones, as the more expeditious method. In a few cases, as in dead-parallel files, the blanks are planed in the planing machine. The blanks are slightly greased preparatory to being cut. A few years ago the Editor witnessed the operation of file-cutting at the establishment of Messrs. Beardshaw, Stevenson and Co. of Sheffield, who have recently permitted our artist to make sketches for the three engravings, Figs. 906, 907, and 913. Writing on this subject soon after his visit, the Editor remarked in the second volume of his work on the Useful Arts" It is scarcely possible to examine attentively the teeth of a fine file, without being struck with their beauty and regularity; but how greatly is our admiration increased when we know that these teeth are cut singly with a hammer and chisel, the workman having no other guide than delicacy of touch and precision of eye, depending however rather upon the former sense than the latter. The cutting room is a long narrow apartment with a range of windows in front, opposite which are placed a number

(1) Published under the direction of the Committee of General

Christian Knowledge.

used in cutting triangular and half-round files. Rasps, | a vertical inclination of about 12° to 14° from the peras already noticed, are cut with a triangular punch pendicular, as represented in Figs. 909, 911, supposinstead of a chisel, every new tooth being placed ing the tang of the file to be on the left-hand side. opposite a vacant space in the adjoining row of teeth. The blow of the hammer upon the chisel causes the The curved surfaces of files show in a remarkable latter to indent and slightly to drive forward the way the skill of the file-cutter: in them the teeth are steel, thereby throwing up a trifling ridge or burr ; formed with straight-edged chisels, many rows of the chisel is immediately replaced on the blank and short cuts being made from the top to the bottom of the file, and these cuts uniting together at their extremities thus form a complete series of lines, passing completely round the cylinder or half-cylinder as the case may be. In fine round files, as many as from ten to twenty rows of cuts are required to cover the surface with teeth; and when it is considered that there may be upwards of a hundred teeth within the space of an inch, some idea may be formed of the many thousand blows required to raise the teeth on a fine file. In double-cut files, when one row of teeth is completed, a fine file is run slightly over them, and the surface is greased to moderate the roughness before commencing the second row." In some of the double-cut gullet-tooth saw-files, Section 10, as many as 23 courses are sometimes used for the convex face, and only 2 courses for the flat one. The half-round and round files are usually cut by apprentice boys, the narrow cuts being less difficult than the broad ones. It might be supposed that all this labour might be saved by using chisels curved to the proper section, instead of straight ones; this plan has been tried and found to be quite impracticable.

one bevil is a little more inclined than the other: the edge is rounded off in order to indent rather than cut the steel. The hammer used with this chisel weighs about 7 or 8 lbs. Fig. 909, is the chisel used for cutting the small superfine Lancashire files: it is 2 inches long and inch wide; very thin and sharpened at about the angle of 35 degrees; the edge is also slightly rounded: it is used with a hammer weighing one to two ounces. The largest files are cut by men : the smallest by women and girls.

Mr. Holtzapffel describes the operation of cutting in the following terms:- "The first cut is made at the point of the file, the chisel is held in the left hand at a horizontal angle of about 55° with the central line of the file, as at a a, Fig. 910, and with

Fig. 910.

Fig 911.

slid from the operator, until it encounters the ridge previously thrown up, which arrests the chisel or prevents it from slipping further 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 preceding 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 nearly as possible of uniform strength; and the process is repeated with considerable rapidity and regularity, 60 to 80 cuts being made in one minute, until the entire length of the file has been cut with inclined, parallel, and equidistant ridges, which are collectively denominated the first course. So far as this one face is concerned, the file, if intended to be single-cut, would be then ready for hardening, and when greatly enlarged its section would be somewhat as in Fig. 911." 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 only a few degrees horizontally, or about 5° to 10° from the rectangle, as at bb, Fig. 910. "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 burrs, 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 towards the point of the file, and when highly magnified, much resemble in character the points of cutting tools generally, as seen in Fig. 911; for the burrs which are thrown up and constitute the tops of the teeth are slightly inclined above the general outline of the file, minute parts of the original surface of which still remain nearly in their first positions. Taper files require the teeth to be somewhat finer towards the point, to avoid the risk of the blank being weakened or broken in the act of its being cut, which might occur if as much force were