• Published in Ducriptions des Machines et Procedes specifies dans les Brevets d Invention, Ac Par if. Christian. Pari; 4to, 1824. Tome 6, p. 33. Patent dated 6 Jan. 1795.

According to the drawings referred to, the file is attached to a screw slide, which is suspended at the ends by pivots, and covered with a thin plate of tin; the slide rests upon a stationary anvil, and is actuated by a guide screw, which is moved at intervals, the space from tooth to tooth by a pin wheel, for which the ratchet wheel would be now substituted. The chisel is held by a jointed arm, beneath which is a spring to throw up the chisel from off the file, the moment after a drop hammer, which is also fixed on a joint, has indented the tooth. The movements of the slide and hammer are each repeated at the proper intervals, in every revolution of the winch handle, by which Thiout's machine is represented to be worked.*

The practical introduction of machinery for cutting files appears to be due to a Frenchman of the name of Raoul, at about the close of the last century, but the description of the machine has not been published, and the manufacture is now carried on by his son, some of whose files are in the possession of the author. They are certainly beautiful specimens of workmanship, being more strictly regular, and also less liable to clog or pin when in use, than files cut by hand, as usual.

His manufacture is principally limited to watch files with flat sides, and measuring from 3/4 of an inch, to 5 or 6 inches long. When magnified, the teeth of the files, cut either by hand or machinery, appear as nearly as possible of the same character.†

Machines have been recently constructed in England for cutting both large and small files, and half a dozen or more at a time.* The details of the machines display great ingenuity and skill, especially in the arrangement for holding the blanks and the chisels, and also in the introduction of templets and other mechanism, by which, in cutting taper files, the hammer is less raised in cutting the ends of the file than at the middle, so as to proportion the force of the blow to the width and depth of the cut, at different parts of the file. Two machines were used for double-cut files, the bed of the one inclined to the right, of the other to the left, to give the different horizontal inclinations proper to these teeth; and a machine with a straight bed was used for single-cut floats, and for round and half-round files. Considerable difficulty was at first experienced in the manage-ment of the chisels, which were then very frequently broken, but with more dexterous management it is ultimately considered that the chisels last for a longer time in the machines, than when used by hand. The machines make about 240 strokes in the minute, or three times as many as the file cutter, with the advantage of nearly incessant action, as unlike the arm of the workman, the machines are unconscious of fatigue; moreover, to save the delay of adjustment, two beds for the files are employed, so that the one may be filled whilst the blanks in the other are being cut, and two frames for the chisels are also alternately used. Taking all these points into account, each machine is considered by the proprietors, nearly to accomplish the work often men, but there are various drawbacks that prevent, under ordinary circumstances, any great commercial advantage in the machine over the hand process, from which considerations, the patent file cutting machines, are not at present used.

* See Thiout's Traiie de l'Horlogerie. Paris, 1740. Vol. 1, page 81, plates 33 and 34.

† Mr. Raoul was rewarded for his files by the Lyce'e des Arts, an institution that no longer exists, but which was founded soon after the French Revolution, for the reward of national discoveries and improvements. From the Report of the Lyceum of Arts it appears, that on the 10th Thermidor, year 8 of the Republic (July, 1800), an honorary crown was decreed to Citizen Raoul for the perfection of his files. And on a subsequent page of the report, is given the opinion of a Committee appointed to examine into the comparative merits of Raoul's files, from which report it appears, they were pronounced by the Committee to bo equal, and even superior, to the best English files.

In concluding this section, there remain to be introduced, two propositions for the manufacture of files, suggested by a very talented and philanthropic member of the scientific world, the late Sir John Robison, K.H, F.R.S.E., late President of the Royal Scottish Society of Arts, etc, namely, his methods of making curvilinear files, and of cutting flat files with very fine teeth. The subjects cannot be better stated than by quoting Sir John's correspondence with the author; speaking of the

• Captain Ericeson's Patent File Cutting Machines, specified 1836, constructed by Messrs, Braith waites of London, and carried into practical effect by Messrs. Turton & Sons, of Sheffield.

842 SIR JOHN robison's curvilinear files, and curvilinear files of the Section Q., page 821, he introduces the subject as follows: -

"I have just entered on a new project, of which I should be glad to know what you think. Having always found difficulty in filing hollow surfaces, from the scratches which the irregular cutting of even the best half-round, or round files, leave in the work, in spite of every care, I was lately led to consider whether half-round, or even round files, might not be made as perfect in their cutting as flat ones. It has occurred to me, that this object may be attained 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 the round file, by pressing the plate round a cylindrical mandrel.

"I do not think that the files made in this way should cost more than those now made, as the surface would be cut by two courses of cuts (as flat files are), instead of the numerous courses required to cover the surface of round files, the saving in this respect would make up for the time required in bending the plates." * * * *

A valuable addition to Sir John's proposal occurred incidentally; Messrs. Johnson and Cammell, to whom the scheme was communicated, in the haste of putting it to trial, took a thin equalling file that had been previously cut on both faces. The equalling file was softened, bent, and re-hardened, and this produced a file, the convex and also the concave surface of which were both useful additions to the tools of the general mechanician.

But it was found that with a plate of equal thickness, the central part bent more easily than the edges, making the curve irregular. This was successfully obviated by making the blank thinner and more flexible at the edges, somewhat as a half-round file, and in which case the bending was quite successful, and the section became truly circular.*

Sir John Robison's second project in respect to the manufac-

* The Society for the Encouragement of Arts, of London, bestowed its silver medal on Sir John Robison for his invention of the curved file, which distinction it is to be regretted arrived as a posthumous honour. (See Trans. Soc. of Arts, vol. liv., p. 128.) And the Royal Scottish Society of Arts presented, in November, 1843, a silver medal to Messrs. Johnson, Cammell, and Co., for the skilful manner in which they had carried out and perfected the above scheme, and introduced the curved files as a regular article of manufacture. (See the official report in the Edinburgh New Philosophical Journal for January, 1844, p. 86.) ture of files, refers to a new mode of forming the teeth of very fine tiles, otherwise than by percussion; and without delaying the reader by referring to the earlier correspondence on the subject, the author gives a short extract from a letter received a few days before Sir John's death, and also the contents of the packet therein referred to.

"Lest my medical friends should be mistaken, and this malady increase so as to prevent my communicating my project for cutting fine files, I shall now make out a memorandum of my ideas on the subject, and making a scaled packet of it shall enclose it to you. If I get better and reach London, we can discuss the matter together, and if I am put hors de combat, you will consider it your own. * * * * * "It appears to me that the graver may be applied with good effect in cutting the teeth of the finer classes of Hat files, and that if a number of steel blanks were firmly embedded on a platform similar to the bed of a planing table, and made to move forward in their own plane by a micrometer screw, then if an equal number of gravers were to be fixed in a frame to lie over the platform, so that each graver point should be in a certain relative position to one of the blanks, on motion being communicated to the frame in a proper direction, and to a distance a little exceeding the breadth of the blank, a line would be ploughed out of the surface of each blank. If the frame were then brought back to its first position, and the platform advanced or receded by the micrometer screw, a second movement of the cutter frame would produce a line parallel to the first, and so on in succession. "If the points of the gravers, instead of being set to cut equilateral grooves as at A, were inclined so as to cut them as at B, then, by a proper proportioning of the depth of the cut, and the progressive movement of the platform, a regular cutting tooth of great sharpness may be given to the file.

General And Descriptive View Of Files Of Less Usua 200221

"The movement to be given to the graver frame may be an oscillating one round a distant center, so that the short arc of the teeth may be sensibly a straight line.

"It is evident that the sharpness and smoothness of the engraving must depend mainly on the way in which the cutter is presented to the work, and experience shows that the position of the tool in the hand of the engraver is the most favourable, both to the production of clean lines, and the preservation of the point of the tool; the graver must be supported endways, and not alone by fastenings in its middle, like the tool of a planing machine, or a slide rest cutter.

"The means of regulating the depth of the cut, and the other arrangements of the parts of such a machine, would of course require consideration by engravers and practical mechanics.

"(Signed) John Robison.

"Edinburgh, 17th February, 1843."

The author much regrets that the multiplicity of his engagements, and especially those connected with these pages, should have prevented him putting the above project to experimental proof, but he would be well pleased to hear that the subject had been brought to successful issue, by any person more favourably situated for carrying out the suggestion.*