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Watchmakers' Hand Book

Part III,
HEALTH AND MANIPULATION
Page 2

TO FILE FLAT WITH ONE HAND.

      224. When an object is to be held on a cork or wood block fixed in the vise, with one hand, and filed with the other had, special care most be taken to lay the file flat without any hesitation after each return stroke, and the hand should be able to feel if the file is wrong in this respect, and to at once bring it flat. After the pupil has learned this, he will very soon be able to adjust the pressure and the force exerted in moving the file horizontally, so that it shall remove an equal amount from the entire surface operated upon. It often happens that the object can conveniently be rested upon a finger of the left hand while the right hand holds the file. The maintenance of the file flat is in that case much easier.

      225. Mechanical device for filing flat. This (the pradel) consists in placing behind the workman a horizontal bar, on which rest one end of the file handle, prolonged for the purpose to about a yard in length; thus the file has two points of support: the bar, adjusted at a convenient height, behind the workman, and the object to be filed flat fixed in the vise in front.

      This method, while convenient for amateurs, may be utilized in teaching an apprentice, letting the supports be hinged at one and press at the other end on a rather strong spring index, which must be prolonged so as to be brought under the eye of the pupil.

      The displacement of the index will show him every false movement of his hands, and will guide him in adjusting them. It would be best if the prolongation of the handle were as light as possible, but rigid and arranged so that the file can be held naturally.

TO TURN CYLINDRICAL PIVOTS, ETC., AND SQUARE SHOULDERS.

      226. Just as in working with the file, advice and demonstration by a good master are here indispensable.

      The materials should be worked in the same order as is explained in parts 221-4; that is: wood, brass, iron, steel, hardened and tempered steel; no one sample being set aside until the student can turn it perfectly round, flat on shoulders, etc., and smooth throughout.

      He should turn for a long time, whether it be by the lathe or bow, exclusively with the point of a square, or lozenge-shaped graver, the end of which is ground off on a slope; this is the only possible method lf learning to turn true, and it enables the workman to acquire great delicacy of touch.

      Owing to carelessness, or to the fact that, when first beginning, then were set to work on metal that was too hard or rough, most learners turn with gravers that are ground to very blunt points; as the graver bites less, they are obliged to apply a proportionately increased pressure, and only succeed in tearing the metal away, subjecting it to a kind of rolling action, and rendering the hand heavy. If a pupil will not practice turning with the graver point, so as to preserve it intact for some time, dependent on the nature of the metal, he will never be able to turn perfectly true.

      The bow should be used through its entire length, and with a motion that is progressive, not jerky. The knack of the turner with the bow consists mainly in keeping the simultaneous actions of the two hands quite distinct; one drawing the bow downwards, while the other depresses the point of the graver supported on the T-rest, and these two movements of the hands must be performed at the same time, but quite independently.

      Irregular and sudden depressing of the graver point, or engaging it too deeply, causes its frequent rupture. This also sometimes arises from the fact that the point is not removed with sufficient rapidity, so that on raising the bow the metal catches it while traveling in the reverse direction; the graver is thus drawn slightly towards the work, and its point will be found too close in when the bow again descends.

      As has been already observed, the bow, which must not be too short, should be used to its full length with a regular, but not rapid motion. Afterwards, when the hand has learnt how to manage the graver, the speed can be gradually augmented. There is always a danger of losing time, teaching, and, therefore, money, if pupils are too much hurried in their lessons. Before trying to work quickly, they should, at any rate, know how to work fairly well.

      Short and sudden movements of the bow will make the object turned jerk; it will be heated, and the sharp angles of the graver will jamb in the metal; thus there is less work done, although there is more noise, and this is done badly.

      227. When sufficient experience has been gained in turning with the graver point, and a trial is made with the cutting edge, do not attempt to remove much at a time by pressing heavily, but take the metal sideways so as to remove a continuous thread, using all the points of the edge in succession and the entire length of the bow. The metal will thus be removed as a thin ribbon or shaving. When the hand has had some experience, it will be found easy to remove long strips, and the work can be done quickly, although there be no hurrying in the movement of the bow. These remarks are equally applicable to turning with a lathe.

      228. Hardened steel that has been let down to a blue temper requires certain precautions. If the graver is found not to cut cleanly, it must at once be sharpened, and no attempt should be made to remove more metal by increasing the pressure of the hand, because the steel will burnish and become hard under a point or edge that is blunt, and the portions thus burnished are sometimes so hard as to resist the best gravers. The only way of attacking them is to begin at one side with a fine graver point which must be sharpened for each stroke; at times it becomes necessary to temper the metal afresh before it will yield. It is asserted that by moistening the point of the graver with petroleum it becomes more able to attack hard substances, and that a mixture of two parts petroleum and one part turpentine enables it to turn very hard steel with comparative ease. Indeed, for all turning it is a common practice to moisten the graver with oil, water, turpentine, or simply by introduction into the mouth.

      We have frequently seen apprentices, and even watchmakers, themselves, careless as to the proper sharpening of their gravers and thinking that they could hasten their work by the application of considerable pressure; they thus produced bright spots that required several hours of work before they could be removed.

      There is one essential condition of ensuring good work with the lathe, and this consists in the perfect roundness of the points or holes of the runners or centers, and of the holes or points that are supported in them; this perfect truth is nevertheless very rarely met with, for it is noticeable that barely one watchmaker in ten knows at the present day how to roll such a point. We shall subsequently indicate the precautions to be observed in order to secure this accuracy.

      The diameter of ferrule is also to be considered; if it is too small, the bow will slip and the object will only rotate by jerks; if too large, it loads the object unnecessarily and the velocity of rotation is reduced, since for the same stroke of the bow the ferrule must make a less number of turns. Moreover, if it is of large diameter, only a light bow must be used, because otherwise the force applied would be excessive.

      Swiss workmen--at least the great majority of them--turn with the right or left hand indifferently. This is a very useful accomplishment easily acquired when young.

      The working of various tools, such as the English or Geneva mandrel, and any lathe driven by a treadle, will be a great help in developing the sense of touch and in making it more certain.

      But it must not be forgotten that, in order to turn well, the lathe must be well made and planned; without this, no accurate work can be done. The lathe is the first and most important of tools, and a great number of very serviceable accessories can be added to it, which, unfortunately, but few watchmakers know how to make properly. As a rule they content themselves with a simple pair of finishing turns on which but a comparatively small amount of work can be done.

      Without committing the mistake of having a too great multiplicity of tools, let the pupil rest certain that a well-planned set of tools in good condition both facilitates and abridges his work and renders it more perfect.

Submitted by: Samuel Kirk (##)

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