on the journal ¿5, of the screw projected beyond the box d; i, is a small pawle or click, jointed to one arm of the wheel h, and taking into the teeth of the ratchet-wheel; k, is a vertical rack-bar, so applied to and sustained by an upright lever l, moving on a pin or fulcrum m5, projecting from the main framing, as to be capable of being moved up and down ;— the said rack, when thrown against the spur-wheel h, engages with it. A connecting-rod m, is jointed at its lower end to the lower end of the rack-bar, and at its upper end to one arm of a crank-lever n, which vibrates on a fixed fulcrum at 0. A small pin or stud p, projects from the side of the sweep or connecting-rod G, and in such a manner as not only to come in contact with the pendant arm of the crank-lever n, when the sweep G, is moved rearwards, but to force the said arm backwards, and so actuate the lever as to elevate the rack-bar k, to the extent required to cause the wheel h, to rotate; which motion will carry the pawle i, against the ratchet-wheel g, of the screw c, in such a manner as to turn the screw a little, or to the extent required, in its bearings; and thus move the carriage w, and its file a short distance rearwards, or the distance required for the cutters to make another closing upon the file. The extent of motion of the screw (which motion determines what is termed the fineness of the cut or width of the teeth of the file) is regulated by putting a pin q, in one of a series of holes r, r, r, made in the lower end of the rack-bar k, (see fig. 5,) which rests upon the pin q; and as the rack-bar is connected, as before stated, to the crank-lever n, the higher the said pin is raised, the more it will draw the pendant arm of the crank-lever n, backwards or towards the rear of the machine; so that the stud P, of the sweep G, will not strike it so soon as it otherwise would. As the said stud p, continues to move through the same distance (the amount of throw of the connecting-rod or sweep G, being determined before the machine is put into operation), the amount of rotation of the screw c, will depend on the extent of motion given by the stud p, to the crank-lever n.

In order to throw the rack-bar k, out of gear with the wheel h, when it may be necessary to stop the operation of the machine, the lever l, is connected to a long horizontal

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shifting-levers, by a rod t, jointed to both. The shiftinglever s, turns upon a fulcrum u, supported by a bracket from the framing, and is connected with a clutch v, which slides. over a feather-edge on the driving-shaft B, by means of a rod 1, and vibrating-lever 2, and is intended to take into a clutch-box, attached to the fly-wheel, and connect or disconnect the driving-shaft B, and fly-wheel c, as circumstances may require. The power by which the machine is driven may be applied to a crank, projecting from the fly-wheel, or to a pulley or other equivalent, affixed to it. When the shiftinglever is moved, so as to gear or connect together the fly-wheel and driving-shaft, it is kept in its position by a small lever w, (see fig. 4,) having a knob x, by which it may be elevated or forced down. The lever w, rocks on a fulcrum at y; the inner end of it has a bent spring z, resting on it, the shape of which will be seen in fig. 3. There is a small projection or stud a1, applied to the under side of the carriage w, as shewn in fig. 3; the said projection should be made adjustable thereon, and should be so disposed, that at the completion of the last teeth, or the two rows of teeth of the file, it will strike or be moved against the top part of the spring z, and force that spring down, so as to trip the lever w, or depress its inner end; by which means its outer end will be raised sufficiently to allow the shifting-lever to move laterally. When thus released, a spring b1, (which is connected by a rod 3, to the lever 2, of the clutch v,) will throw the clutch out of connexion with the fly-wheel, and stop the action of the machine. c1, is a cog-wheel, fixed on the journal of the screw c, and gearing into a spur-gear d1, fixed on one end of a shaft e1 ; which shaft has a small crank-wheel f1, on its other end, at the front end of the machine. The object of the various parts, just above described, is to enable a workman, by turning the crank-wheel f1, to readily and quickly rotate the screw c, in a direction necessary to create a return movement of the carriage w, to the extent required to commence cutting another file. The next portion of the machinery to be described is that by which the cutters, during any increase or diminution of the thickness of the file, are caused to operate on it by a uniform pressure, so as to cut to a uniform depth.

The operation of cutting the file always commences at its smaller end, or the opposite end to that on which the shank is made; from this end the file usually increases in thickness towards its middle part, from whence to the shank it is generally of about a uniform thickness; but it is necessary that, during the whole of the operation, a uniform pressure of the cutters on the file shall be preserved. It will be understood, that the sliding carriage L, cannot advance so far forward at each closing of the cutters on the file as it did at the preceding closing of them; or, in other words, its range of motion forward is diminished a little at each operation of the cutters: this results from the peculiar manner in which it is connected to the levers, by which the cutter-slides are operated; consequently it will be seen that the obtuse angle of the toggles or progressive levers gradually decreases while the file is being cut towards its middle part. This creates a loss of power applied to the cutters, to cause them to enter the file to the required depth. In order, however, to make up for this loss, the compensatory machinery is employed, which will now be described.

The lower end of the lever H, is connected to a horizontal sliding-bar g1, (placed at the lower part of the machine) by mcans of a bent bar h1, jointed to both the lever and slidingbar. The bar g1, is sustained in proper bearings, so as to move backwards and forwards longitudinally. At its front end this bar g1, is furnished with a series of notches or teeth k1, into which a projection 1, from a small lever m1, (see fig. 4,) catches. This lever m1, vibrates upon a fulcrum n1, and is connected to a short lever o1, (placed above it and adjacent to the disc or circular plate D, of the driving-shaft, as shewn at fig. 4,) by a bar p1, jointed to both. The lever o1, rocks. on a fulcrum q1, when it is struck on the top edge of its inner arm by a small cam r1, which is affixed to the revolving disc D, for that purpose, and comes in contact with the lever at every revolution of the disc. By this means (the outer arm of the lever o1, being raised, as its other arm is depressed) the lever m1, is raised sufficiently to remove the projection or catch 1, out of contact with the notches of the sliding-bar g1. The object of the notches k1, and mechanismi connected with

them, as last specified, is to maintain the position of the bar g1, as it is gradually forced forward, while the file is being cut from its point or smaller end to its middle part. The sliding-bar g1, has a cord s1, fastened on to it, and extending from it to a barrel or pulley t1, fixed on a horizontal crossshaft u1; the outer end of which carries a peculiarly-shaped cam v1, as shewn at figs. 2, and 5. The periphery of this cam is grooved out, so as to receive a cord w1, one end of which is fastened to that part of the periphery of the cam which is nearest to the shaft. From the said cam the cord w1, proceeds to, and is wound around, and attached to, a pulley or drum æ1, mounted on an axle, having its bearings in the framing. Around this drum another cord y1, is also wound; which cord extends downwards, and is tied to a long lever or bar z1, which vibrates on a fulcrum at a2, and has a weight 62, hung on it, as seen in fig. 2. The front end of the lever z1, passes through a vertical slot c2, made in an upright d2, (see fig. 4). Near the inner side of the lever z1, a sliding-bar ƒ2, is placed, and is supported by an arm g2, (fig. 5,) and the upright d2, through both of which it is free to move in a longitudinal direction. It has an arm or stud h2, projecting from a slider i2, fitted to slide on the bar and be fixed thereon by a set-screw k2, (see fig. 1). The stud h2, rests against the iron trammel 12, of the weight b2. The sliding-bar ƒ2, has one end of a horizontal lever m2, jointed to it, or made to project through a slot cut in a piece of plateiron n2, affixed to the bar. The lever m2, works on a fulcrum 02, at its opposite end; and at its middle it is jointed or connected to the lower arm of a vertical lever p2, which turns on a fulcrum q2, projecting from a longitudinal fixed or stationary bar r2. At its upper end the lever p2, is connected to a pawle or lever s2; one end of which rests in one of a series of notches 12, made in a plate u2, which is screwed to the slide or carriage w; and the other end of the pawle or lever s2, carries a projecting pin, which is made to traverse an irregular slot v2, w2, x2, y2, formed in a piece of metal ≈2, screwed on to the top girt a3, of the frame. From y2, to a2, the slot is horizontal, while from a2, to w2, it inclines downwards, and from w2, to v2, it is again horizontal. The object

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of the lever p2, and its pawle s2, is to impart (by reason of the inward movement of the carriage w,) a forward motion to the slide-bar f2, whereby its stud h2, will be made to press against the trammel 12, of the weight b2, and slide it forwards on the lever z1, and thus increase the power of the weight on the cord y2; which increase of power is disseminated through the mechanism to the cutters. As the cutting operation progresses towards the middle of the file, it becomes necessary that the weight 62, should gradually be moved towards the front end of the lever on which it hangs. This is effected by the carriage w, which gradually presses the upper arm of the lever p2, back, until the pin of the lever s2, falls into the inclined part w2, x2, of the slot v2, w2, x2, y2. While the pin is passing down the said inclined part, the rear arm of the lever s2, will be tripped up, so as to raise its front arm out of the notch of the plate u2. This being effected, the slide w, will continue its inward progress without further acting upon the lever p2. The tripping of the lever or pawle out of the notch takes place when the cutters have reached the middle or thickest part of the file. Each of the slides o, o, before mentioned, as sliding between the grooves N, N, has an arm b3, extending rearward from it, and supporting a female screw-bearing or box c3. A screw-shaft d3, extends through these screw-boxes, and is provided with two male screws e3, ƒ3, one being what is termed a right-threaded and the other a left-threaded screw. A hand-wheel g3, is fixed on one end of the screw-shaft d3, while on the other end a ratchet-wheel h3, is fastened. Into this wheel a pawle, connected with the lever i3, takes, and is held in contact therewith by a helical spring. The pawle-lever i3, is arranged as shewn in the drawings, and vibrates, in a vertical direction, on a fulcrum at k3. To the inner end of this lever a spring-chain 73, is attached, which extends downwards, and is fastened to a pin m3, projecting from the rear side of a circular plate n3, fixed on the shaft u1, which carries the cam-piece v1. The object of the two right and left-threaded screws on the screw-shaft d3, is to enable an attendant to set the edges of the chisels to their proper distance apart when they commence to cut at or near the top or small end of any file. The use of the ratchet