Names of some of the Files, corresponding with the Sections A to Z. (represented on page 821).
Square files, both parallel and taper, some with one safe side; also square rubbers.
When large, cotter files; when small, verge and pivot files.
Hand files, parallel and flat files; when small, pottance files; when narrow, pillar files; to these nearly parallel files are to be added the taper flat files.
When parallel, equalling clock-pinion and endless-screw files; when taper, slitting, entering, warding, and barrel-hole files.
French pivot and shouldering files which are small, stout, and have safe-edges; when made of large size and right and left they are sometimes called parallel V files, from their suitability to the hollow V V's of machinery.
Name and purpose similar to the last.
Flat file with hollow edges, principally used as a nail file for the dressing case.
-Pointing mill-saw file, round-edge equalling file, and round-edge joint file; all are made both parallel and taper.
Round file, gulleting saw file, made both parallel and taper.
Frame saw file, for gullet teeth.
Half round file. Nicking and piercing files, also cabinet floats and rasps; all these are usually taper. Files of this section which are small, parallel, and have the convex side uncut, and have also a pivot at the end opposite the tang, are called round-off files, and are used for rounding or pointing the teeth of wheels, cut originally with square notches. The pivot enables the file to be readily twisted in the fingers to allow it to sweep round the curve of the tooth to be rounded.
Cross, or crossing files, also called double half rounds.
Oval files; oval gulletting files for large saws, called by the French limes a double dos. Oval-dial file when small.
Balance-wheel or swing-wheel files, the convex side cut, the angular sides safe.
Swaged files, for finishing brass mouldings; sometimes the hollow and fillets are all cut.
Sir John Robison's curvilinear file, to be hereafter described.
Triangular, three-square, and saw files, also triangular rubbers, which are cut on all sides. Triangular files are also made in short pieces, and variously fixed to long handles, for works that are difficult of access, as the grooves of some slides and valves, and similar works.
Cant file, probably named from its suitability to filing the insides of spanners, for hexagonal and octagonal nuts, or as these are generally called, six or eight canted bolts and nuts; the cant files are cut on all sides.
When parallel, flat-dovetail, banking and watch-pinion files; when taper, knife-edged files. With the wide edge round and safe, files of the section T, are known as moulding files, and clock-pinion files.
Screw-head files, feather-edge files, clock and watch-slitting files.
Is sometimes used by engineers, in finishing small grooves and key ways, and is called a valve file, from one of its applications.
A file compounded of the triangular and half-round file, and stronger than the latter; similar files with three rounded faces have also been made for engineers.
Double or checkering files, used by cutlers, gun-makers and others. The files are made separately and riveted tog with the edge of the one before that of the other, in order to give the equality of distance and parallelism of checkered works, just as in the double saws, for cutting the teeth of racks and combs, sec p. 723.
Double file, made of two flat files fixed together in a wood or metal stock; this was invented for filing lead pencils to a fine conical point, and was patented by Mr. Cooper under the name of the Styloxynon.
The manufacture of files. - The pieces of steel, or the blanks intended for files, are forged out of bars of steel, that have been either tilted or rolled as nearly as possible to the sections required, so as to leave but little to be done at the forge; the blanks are afterwards annealed with great caution, so that in neither of the processes the temperature known as the blood-red heat may be exceeded. The surfaces of the blanks are now rendered accurate in form and quite clean in surface, either by filing or grinding. In Warrington, where the majority of the files manufactured are small, the blanks are mostly filed into shape as the more exact method; in Sheffield, where the greater number are large, the blanks are more commonly ground on large grindstones as the more expeditious method, but the best of the small files are here also filed into shape: and in some few cases the blanks are planed in the planing machine, for those called dead-parallel files, the object being in every case to make the surface clean and smooth. The blank before being cut is slightly greased, that the chisel may slip freely over it, as will be explained.
The file cutter, when at work, is always seated before a square stake or anvil, and he places the blank straight before him. with the tang towards his person, the ends of the blank are fixed down by two leather straps or loops, one of which is held fast by each foot.
The largest and smallest chisels commonly used in cutting files are represented in two views, and half size in figs. 808 and 809. The first is a chisel for large rough Sheffield files, the length is about 3 inches, the width 2 1/4 inches, and the angle of the edge about 50 degrees, the edge is perfectly straight, but the one bevil is a little more inclined than the other, and the keenness of the edge is rounded off, the object being to indent, rather than cut the steel; this chisel requires a hammer of about 7 or 8 lbs. weight. Fig. 809 is the chisel used for small superfine Lancashire files, its length is £ inches, the width 1/2 inch, it is very thin and sharpened at about the angle of 35 degrees, the edge is also rounded, but in a smaller degree; it is used with a hammer weighing only one to two ounces, as it will be seen the weight of the blow mainly determines the distance between the teeth. Other chisels are made of intermediate proportions, but the width of the edge always exceeds that of the file to be cut.
The first cut is made at the point of the file, the chisel is held in the left hand, at an horizontal angle of about 55 degrees, with the central line of the file, as at a a fig. 810, and with a vertical inclination of about 12 to 4 degrees from the perpendicular, as represented in the figures 808 and 809, supposing the tang of the file to be on the left-hand side.* 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 burr, 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 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 equi-distant 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. 811.*
• A foreman, experienced in the manufacture of Sheffield files, considers the following to be nearly the usual angles for the vertical inclination of the chisels: namely, for rough rasps, 15 degrees beyond the perpendicular; rough files, 12 degrees; bastard files, 10 degrees; second-cut files, 7 degrees; smooth-cut files, 5 degrees; and dead-smooth-cut files, 4 degrees.
Most files, however, are double-cut, or have two series or courses of chisel-cuts, and for these the surface of the file is now smoothed by passing a smooth file once or twice along the face of the teeth, to remove only so much of the roughness as would obstruct the chisel from sliding along the face in receiving its successive positions, and the file is again greased.
The second course of teeth is now cut, the chisel being inclined vertically as before or at about 12 degrees, but horizontally, only a few degrees in the opposite direction, or about 5 to 10 degrees from the rectangle, as at b b, fig. 810; 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 of courses, fill the surface of the file with teeth which are inclined towards the point of the file, and that when highly magnified much resemble in character the points of cutting tools generally, as seen in fig. 811, 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.
If the file is flat and to be cut on two faces, it is now turned over, but to protect the teeth from the hard face of the anvil, a thin plate of pewter is interposed. Triangular and other files require blocks of lead having grooves of the appropriate sections to support the blanks, so that the surface to be cut may be placed horizontally. 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 used in cutting, the teeth at the point of the file, as in those at its central and stronger part.