PART VI.
PRACTICAL RECIPES.
495. The practical operations of the watchmaker are numerous and of a very varied character. Detailed instructions in regard to the proper conduct of a large number of them will be given in this part of the work, and frequent references will be made to former parts of this volume, whenever by so doing repetition can be avoided.
The operations herein discussed are often of so dissimilar a nature that it has been found impossible to classify them in such a manner that will always ensure the reader finding the information he requires without waste of time; and any risk of this would seriously impair the value of such a hand-book as the present. A very full index has therefore been added, and when seeking for details concerning any particular operation, this should in all cases be first consulted.
THE PLATE.
496. To Make a Plate. The sheet of brass having been prepared in the manner explained in article 103, roughly rounded and smoothed on one face, is cemented to the chuck of a lathe. Turn out the other face of the plate very flat, and make the circumference square.
When using a lathe the face must first be roughed out, and then the plate is to be cemented to a perforated plate, so that it can be centered and finished. Smooth the exposed face with a well-set cutter and turn the inside and outside of the edge; then make sure that the whole is concentric by a light cut with a cylindrical drill in the center hole. After removing and cleaning the plate it is set up in the dogs, and the face that has hitherto been untouched is gently dressed with the graver.
There will thus be left a narrow ring at the edge that is not touched by the graver: this may be levelled with a smooth-cut file, and the whole surface then smoothed as explained in article 171.
If a lathe is not available, the plate must be cemented to an arbor of the form shown at Y, Fig. 229. The heel of this is received in a runner of the turns, while the point of the opposite runner is received by the hole in the center of the plate, which is thereby held in close contact with the plate of Y, the revolution being, of course, produced by a bow. While the cement is still hot, a stick resting on the T-rest will serve to ensure the concentricity of the plate until it is set. This setting may be rendered more rapid by the application of cold water.
Turn out the plate with a hooked graver made of a worn out file, and, if the upper or under side does not run true, turn the portion that projects beyond the chuck with a graver, and, when the plate is removed, face the surface, taking the flat ring produced by the graver as a guide, and taking care to avoid altering any portion of it.
The smaller sinks can also be made in the same primitive manner, to which we have only drawn attention for the sake of watchmakers who are ill-provided with tools. But we would at the same time point out that, at the present day, there should not be a single one who does not know how to extemporize a lathe-head.
497. Cocks and Bars. If it is required to make all the cocks and bars of a watch, prepare a false plate, the thickness of which is a trifle greater than that of the highest cock or bar; then turn on the under side a series of sinks to correspond with the thin portions of the cocks and bars. Cut the several parts out of this plate with a fine saw, and it only remains to shape their contours with a file.
The same method may be adopted if a number of identical cocks have to be made at a time.
THE BARREL.
INCLUDING ARBOR, STOPWORK, MAINSPRING, ETC.
498. To Make a Barrel. Having trued both faces of the brass, and drilled a central hole rather less than that finally required and exactly perpendicular to the faces, turn away the brass from the inside (leaving a considerable excess of metal at the center to form the shoulder), and form the ring on which the teeth are to be cut, if it is a going-barrel, in the ordinary lathe on a wax chuck. Then fasten the plane surface, which must be quite true, to a smooth plate that is of uniform thickness and has a hole in the center to permit the passage of the pump-center. Having fixed the plate by the mandrel dogs, finish with well-set gravers: 1 the inside; 2 the external cylindrical surface both of the barrel and of the ring left for the teeth; 3 the barrel-cover groove; and 4 with a fine-pointed cutter slightly enlarge the central hole. By this means it is possible to ensure that the barrel will turn true and in the flat. Smooth the inside, more especially the groove, the corner of which must always be carefully smoothed and polished.
The cutting of the recess in the barrel-cover (of a Swiss or French watch) that gives freedom to the motion work, as well as the recesses for the stopwork, will not present any difficulty when the workman is provided with a lathe with or without a slide-rest.
When there is no slide-rest, the tool shown at D, Fig. 230, can be used for making the groove. A strip of metal of rectangular section has a small cutter clamped in a slot in its surface at a slight inclination. By releasing the two screws of the clamp, this cutter can be advanced to any required extent, and in the strip of metal are two or three slots having different degrees of inclination, so that the one can be selected that corresponds with the depth of the groove.
499. To Make the Star-Wheel Sink. This is easy on the lathe, the requisite degree of eccentricity being given to the barrel-cover by means of the pump-center.
500. The Cover: Form of the Groove. As in making the barrel, a thick ring must be left at the middle of the cover to be afterwards removed.
Fig. 231 is an enlarged figure to show the mode in which a cover is held in its groove. The two are so formed that the cover shall pass into the recess with the least possible resistance, and yet be held firmly without a risk of rotation. It is, nevertheless, a good precaution to fix a pin in the rim so that it shall prevent such an accident.
501. Barrel Hook. It is necessary to observe that a certain amount of caution must be exercised in regard to the barrel hook, for at least three-quarters of those met with are badly made. A large hook, projecting far into the barrel, as often occurs, occupies a needless amount of space, and at times occasions the breaking of the spring. One that is badly formed or does not project sufficiently allows the spring to escape. A hook should project rather beyond the thickness of the spring; if too thick the spring will be weakened at its eye; if too thin, it is liable to give when the pull of the mainspring is exerted on it.
The circumference of the barrel must be drilled through exactly midway between the bottom and the groove, in a direction that is slightly inclined, so as to resist the pull of the mainspring. A thread is cut in this hole with a conical tap, arresting its advance just before the full threads are reached, in order to make sure that the brass screw to be subsequently inserted shall hold firmly. Then tap the brass wire from which a hook is to be made. Allowing a length to project beyond the screw-plate equal to about one and a half times the thickness of the mainspring, file the two sides flat, round off the point, inclining it slightly backwards, and form the hook with a fine screw-head slitting or other suitable file; then remove the wire from the screw-plate and hold it in a pin vise.
The angle a (C′, Fig. 232) is now filed down so as not to project within the barrel; any burr that might interfere with its introduction is also removed and the hook is then screwed into its place. It will be easy to ascertain whether the various heights, etc., are correct before screwing it tight home. Then screw the hook into position so that it requires the application of some force in doing so and cut off the external portion level with the surface of the barrel, employing a sharp cutting file. But if it appears necessary to withdraw the hook to make any alteration, this should be done before bringing it to the final position.
Some watchmakers do not take such precautions; they fit a piece of hard brass wire to the hole, beveling off the end that is to form the hook, then cut off the wire nearly flush with the outer surface of the drum and, resting the back of the hook against a piece of steel, give a blow with the hammer so as to bend the point of the hook. But this method, although expeditious, is not the best and it does not always succeed.
502. To Repair a Barrel. When the play or the end shake of the pivots is considerable, bush the holes with bushings turned on a smooth taper arbor. They must not be riveted roughly, as there is a danger of distorting the bushing or of causing the bottom of the barrel to “cockle.”
If there is any fear that the bushing will be thus distorted or that the barrel will not run true after the operation, it will be well to employ large bushings in which the hole is less than that ultimately required. Then center from the circumference and enlarge the hole, at the same time truing it.
Some practical watchmakers, if the bottom of the barrel is thin, or if special solidity is requisite, fear that the bushing may become loose; they, therefore, enlarge the barrel-hole and make it square; then bush it with a piece of plain brass, and having centered the barrel by its circumference in the lathe, drill a central hole.
It is hardly necessary to observe that, when the holes in both barrel and cover require to be operated upon, a pin should be fixed so as to prevent the latter from rotating in its groove; so that before finally removing the barrel from the lathe, the cover can be put in position to have its center accurately adjusted with a long pointed graver.
503. A Barrel That Does Not Run True. The remedy for this has just been indicated: enlarge the holes and rivet in them bushings that are either plain or have only very small holes. The two holes can then be accurately centered with a slide-rest and cutter of the requisite form.
It is a very simple process, and yet there are some workmen who, either from not possessing a lathe or ignorance as to how it should be used, set the barrel on a screw arbor, and, after having topped the teeth, round by hand those teeth which have been touched. This method of procedure is longer than the former and gives results that are worse; moreover, since the screw-arbors are rarely themselves true, especially in regard to the cones, which will be found to have a play on the axis, it is far better to set the barrel in cement on an arbor of the form C, Fig. 233, on the center pin of which the barrel-hole fits without play; the middle of plate C must not be too thickly coated with cement.
504. Barrel Out of Upright. Several methods may be resorted to for adjusting a barrel that does not turn flat on its axis. Assume that the holes are not too large, for it has just been shown that by bushing the holes and truing them on the lathe, it is always possible to ensure that a barrel shall be true on its axis.
To true it without renewing the holes, first try turning the cover round in its groove by successive short stages, and test its truth each time; the arbor being clamped in a pair of sliding tongs and a card held close to the teeth. If, after the entire circumference has been tested, no point is found that satisfies the requisite conditions, the edge of the cover must be gently hammered (a piece of silver paper being first laid on the anvil so as to avoid marking the gilding) on the side at which the teeth pass farthest from the card and the effect of the operation must be tested. This hammering should be done very carefully and little at a time, and if too great a strain is put on the cover to force it into the groove, some metal must be removed from the side opposite to that at which the hammering occurred. Hence, if the one side is too much extended in the first instance, so that a large amount of metal has to be removed from the opposite side, the operation is liable to be unnecessarily long and difficult. It is hardly necessary to observe that we are here referring to the modern form of going-barrel, in which the cover is on the opposite side to the teeth; in the older form, where the reverse is the case, the opposite edge of the cover must be hammered.
Sometimes a barrel that runs true on its arbor is found to incline when mounted on the plate: such a fault is due either to the barrel holes being too large or to the sink that receives the ratchet not being parallel to the plate. This sink must be trued in the lathe while in position, screwed to the plate of the watch.
505. To Adjust a Post or Curb in Position. Make a small punch, a front and side elevation of which are shown at p p, Fig. 234; harden it and let it down to a yellow temper at the point. Now fix a flattened ball of lead in the vise, the upper surface of which is so formed that the portion of the barrel that is to receive the hole for the post may rest securely. There is no necessity for the entire barrel to rest on the lead. Place a small piece of mainspring, q, within the barrel against the circumference, where it will be maintained by the punch p, which will also hold the barrel steady on the lead block. Then give a moderate blow with a heavy hammer on the head of the punch, forcing its point through the barrel.
A burr will be produced outside the barrel, while there will be a corresponding depression within, especially in front of the hole. To secure clean edges, pass a file over the external projection, but only sufficiently to remove its crest, and, resting the inside of the barrel on a lead block, drive inwards the metal that projects; then pass the punch through in a direction opposite to the first and of course with less force. Remove the burrs and repeat the operation first on one side and then on the other with gentle blows of the hammer, removing the punch by hand. Finish with a very fine file, which will entirely remove any external burr round the hole, and one cut with a slide-rest cutter in the inside, followed by charcoal and oil.
A watchmaker that has never performed this operation will do well to experiment with the punch on a small plate of brass, or, still better, on a worn-out barrel.
To insert the post, coil up the mainspring in the winder so as to be able to introduce a slightly conical piece of steel or brass between the two last turns of the spring and near to the hole. Place the post in position and hold it and the spring while the wedge that keeps the coils apart is removed. If the opening thus secured was found to be insufficient, it might be increased by introducing a screwdriver, which is held down until the post is inserted. The making of this curb, shown at b, Fig. 234, will offer no difficulty.
506. Stopwork. If the pitch circles of the finger-piece and star-wheel of several Geneva stops be measured, it will be seen that three different proportions may exist (Fig. 235), in which the former is less than, equal to, and greater than the latter respectively.
When the finger-piece has a greater diameter, as at d, it will oppose an increased resistance to the hand in winding, but the direction of its pressure against the stop will be much below the center of rotation of the star-wheel, because the finger is necessarily very short.
When the finger-piece is very small, as at a, there will be less resistance opposed owing to any want of freedom of the star-wheel, and the pressure against the stop will be more nearly tangential, the finger being relatively long; but more care will be required in the construction and, for a given force applied to the key in winding, there will be a proportionately increased pressure against the star-wheel axis.
Inconveniences thus increase in proportion as either piece is enlarged as compared with the other, and the best proportion is secured by making the two diameters equal, as shown at c b.
The stud on which the star-wheel rotates should be cut square or, preferably, slightly conical downwards.
507. To True a Star-Wheel. The form of a star-wheel can be adjusted on the lathe, on the tool shown in Fig. 208, using a cylindrical mill-cutter and adding a stop so that the branches of the tool are always brought to the same distance apart.
Star-wheels can be bought of the material dealers, but they are not always equally divided; indeed, some exist that have been merely punched in the punching press. Hence it follows that many of them are characterized by at least one of the following faults: teeth of unequal length, or with their concavities of unequal form.
When the teeth are well formed and finished at their ends, but of unequal length, this arises from the star-wheel having been badly centered during the operation of cutting; it must then be re-centered. Take a small brass plate H, Fig. 236, and drill a hole at its center, with a notch at the edge, a, to receive the convex tooth without shake. Now place the plate in the lathe and turn out a sink to receive the star-wheel and hold it firmly. The convex tooth will then drop into the notch and the wheel should project a little above the face of the plate. Now release one dog, and, having gripped with it one tooth of the wheel, take a fine-pointed graver and true the central hole and the sink that receives the screw head, taking care only to remove a small quantity of metal at a time.
If the workman has not considerable experience in using the lathe and fears a derangement in releasing and again tightening the dog, he had better remove the plate, cement the star-wheel in position and replace it, when it can be re-centered with the pump-center.
508. To Make a Finger-Piece. After having drifted the square hole in the center of a steel disc of suitable dimensions, and traced out a line to mark the circumference of the disc and the end of the finger, drill two holes a little beyond this line, leaving such a space between them as to ensure that the base of the finger shall possess sufficient strength; but these holes should be drilled so far in towards the center of the disc that freedom is left for the corners of the star-wheel teeth during its rotation. The head of the finger is at first left so as to exactly fit the spaces of the wheel without play, this being subsequently given with a fine file and in the smoothing.
File the circumference all round so as just not to touch the line traced out; then, putting the disc on an arbor, hold a fine barrette file against the edge, and cause the arbor to oscillate backwards and forwards, the file coming in contact alternately with each side of the finger. This smoothing of the rim will materially facilitate and abridge the final work with the graver. The corner of the rim on one side of the finger having been finished off with the graver edge, reverse the arbor between its centers to treat the other corner in a similar manner. A finger-piece made as here explained will be found to be very true.
Some watchmakers, when it is possible, finish the circumference after it has been adjusted on the barrel-arbor itself; but as a rule this is not necessary.
The slit that receives the pin may be cut as follows: File a square piece of brass to fit the hole in the finger-piece, cut a notch across the end with a screw-head file, and insert it in the square hole. Having centered a flat cutter, the thickness of which is equal to that of the slit to be cut, on a taper arbor, place this in the lathe; resting the brass horizontally on the T-rest (which had better be at the back of the lathe, so that the progress of the operation may be more easily observed) and present the notch to the cutter.
509. It will be understood that the foregoing details relate to the method to be adopted in making the finger-piece by hand, but it is very easy to arrange an addition to the ordinary lathe, with or without a throw, for rounding or truing the circumference with great rapidity.
Having mounted a circular mill-cutter on an arbor in a chuck, as seen at R, Fig. 233, replace the T-rest by an upright that has a shoulder, and is truly cylindrical, and of a diameter to fit the support without shake; the finger-piece, D, is fixed to its upper end by a cone and nut, as in the screw-arbor, or by any other means. A lever l is adapted to the vertical rod, so that it can be rotated between two stops on the lathe-bed; such stops are, however, not always needed, because by employing a thick cutter that is smooth on the face there is no danger of damage to the finger. At the same time, if there are no stops, considerable care is requisite in the smoothing and polishing to prevent the sides of the lap touching the finger. This can be polished afterwards in a very short time by using a lap that has been turned on the edge to fit the notch. It is useless to enter into further particulars, as the little appliance or one of an analogous description can be easily made.
The apparatus shown in Fig. 195, and described in article 402, could be employed for such a purpose.
510. To Make a Clock Barrel. A strip of soft brass, thicker than the circumference of the drum is intended to be, is coiled into a circle rather less in diameter than the required barrel, on a cylinder of hard wood, either by pressure between the jaws of a vise, or with a mallet or hammer. The two edges, after being carefully cleaned, are soldered with silver solder or brazed, while they are held in position by a piece of binding wire wound round the drum.
Placing this ring on the nose of a beak-iron, harden it by gentle blows, so as not only to harden the brass, but also to increase the diameter and make a true cylinder.
Chuck it on a cylinder of hard wood in order to turn the two ends square, and form the edge that is received in a groove cut in the bottom of the barrel; the bottom is then soft soldered in position. In the older barrels that contained very strong springs, it was often the practice to leave tongues projecting round the drum that entered holes in the bottom and were riveted on the other side.
The barrel may be cemented to a large wax chuck that has as its center a short arbor tapped and provided with a washer and nut, or it may be gripped by its base in the universal head, and the surfaces, etc., finished.
Some of the details given in regard to a watch barrel are applicable here.
The drum is now no longer made by bending a strip of brass, except in country towns, because brass tubing is always to be obtained in cities at metal warehouses, which only needs to be cut into rings of the requisite length.
511. To Make a Barrel-Arbor. If the metal is in the rough and has the scale on, it must be cleaned either on the stone or with acid. The following method of procedure has been proved in practice to be expeditious:
When the arbor has been turned to shape with the graver, smoothed, and almost polished, it is placed in the barrel and should rotate when in position, but with considerable friction. Then make the two squares as explained below (513); and, after smoothing that which receives the finger-piece, set this latter in position on the arbor and see that it does not descend quite to the shoulder. Then replace it by a worn out finger-piece, or by a copper disc that is cut so as to allow of the insertion of the pin in exactly the same position as is required by the finger-piece to be definitively used. It is then easy to drill the pin-hole from either side of the square and to smooth it with a fine broach. Each time that the arbor has to be inserted in the barrel, great care must be taken to remove any burr, as it might damage the barrel holes.
Before hardening the arbor, cut in it two grooves of moderate depth at the points at which the ends must be broken off. Such a practice has two advantages: 1. The two waste points of the arbor can be removed and each end partly formed without employing a file, an arrangement whereby it is possible to maintain in the arbor a maximum of hardness, at least at the winding end. 2. If the arbor is distorted, it will not be in the body, but from the points at which these cuts are made. If any distortion occurs, the blow-pipe jet can be directed on the points, which are then removed with a file before the final polishing.
512. To harden the arbor, place it in an iron tube and surround it with powdered charcoal which is pressed down, having previously been well dried. When the whole has been heated to the requisite temperature, throw it into water, and, if the precautions already explained under hardening are adopted, the arbor will be found to be smooth and clean and without either scales or blisters on its surface. Clean and polish it; this latter operation will give the proper freedom to the pivots, although it often happens that a touch with a broach is required in the two holes.
The bevelled groove within the ratchet teeth is polished by rotating the arbor while a small steel plate, perforated at its center and of the form shown in plan and section at Z, Fig. 237, is held by the hand against the groove. The shoulders can be easily and rapidly polished in the tool represented in Fig. 44.
513. To Make the Squares. To Make Drifts. The tool shown in Fig. 238 is used. On the plate P, which is at right angles to the foot S, is fixed a frame that carries two hard steel rollers, c and d, the edges of which are extended to form a guide.
A bent finger b is hinged on a screw on the side of the plate, and has a hole j drilled in it, which is continued for a short distance into the plate P.
The following is the method of using the appliance: Fix to the arbor a disc, indicated by dotted lines, in the circumference of which are four equidistant notches to receive the nose of the finger b. The rod S takes the place of the T-rest and the arbor is placed between the centers of the lathe. As S can be raised or lowered to any position and the runners can be moved laterally, it is easy to bring the point at which the square should commence to correspond with the line n n. The finger b having been inserted in one of the notches of the division-plate, reduce the arbor with the file L. Move b to the next notch, and repeat the operation, and so on with the other two sides.
If there is any danger of the finger not maintaining a sufficiently firm hold of the plate, a tight-fitting pin can be inserted in the hole j.
At first the arbor should be filed away less than is actually required, and the only adjustment necessary to ensure this is the raising of S to a suitable height. No difficulty need be experienced in this, but, if any doubt is entertained, a screw may be supported from the bed of the lathe, terminating in a rod that passes through the plate P, as indicated at t for example, thus securing perfect regularity in the upward and downward motion of the system.
If a tapered square is required, it will be sufficient to slightly incline the frame by means of two screws v i, placed near its left-hand edge with their ends resting on the plate P.
514. To Drill Exactly Through the Center of the Arbor. Of course, if the old arbor-nut is available, it will afford the best guide for performing this operation, and, if the arbor is tapped, such a hole will not be required. But when neither of these conditions is satisfied, the workman will have two slight difficulties to overcome: the drilling of the arbor and its nut exactly in the center and parallel to the plane of the ratchet. By adopting the following method, he can easily satisfy these conditions:
515. Take a brass disc D, Fig. 239, turned smooth on its two faces. Enlarge its central hole until the barrel-arbor enters it to such a distance that a blow of a mallet will drive it up against the ratchet where it should hold firmly. This disc is chucked on the lathe and a groove is formed that passes exactly through the center. Ascertain by means of a douzieme or a thickness gauge whether the thickness of the disc, measuring from the bottom of the groove to the under side, is equal to the space between the shoulder of the arbor that corresponds to the outside edge of the barrel hole, and the point at which the hole should be drilled. If the thickness is excessive, diminish it from the under side; if, on the other hand, it is not sufficient, fit some thin discs on the arbor, and then force the brass disc to the position thus determined upon. It is hardly necessary to add that when this is done, holes must be drilled to some depth on either side of the arbor, using a drill that does not shake about in the groove although quite free and inclining slightly downwards so that the hole shall not be above the point determined upon, namely, the bottom of the groove. Continue the drilling until the two holes meet, the drill being maintained, during this part of the operation, parallel to the face of the ratchet.
516. If the workman is not provided with a tool for cutting the groove exactly in the axis of the disc, the accuracy that is so essential can be ensured as follows: A brass rod G, Fig. 240, is divided into four at the end as near the center as possible by means of a fine saw or a file that only cuts with its edge, which will be used to form the groove. Set the rod G in the lathe, a center of the form f being inserted at b where the slits cross, and turn down the rod G b, although only a little metal should need to be removed, until it enters the hole in the brass disc and projects a short distance on the other side. It then only remains to insert in one of the notches of G b the cutting file or the saw previously used, to form a groove on the surface of the disc that passes exactly through its center; it is to be remembered that the saw, etc., must only cut with its edge, and should enter the notch with a very slight friction, sufficient to indicate that it fits without play.
517. The Arbor-Nut. The usual practice is to make the diameter of the nut equal to one-third that of the inside of the barrel. With thick springs of but slight flexibility it must be larger so as to avoid overstraining the innermost coil, and, conversely, with a very thin spring it is diminished, rendering the employment of a longer spring possible. When the nut is too small the spring must be made long, and, by setting up the stopwork, a coil of the spring can be maintained always on the nut.
518. To drill the nut along a diameter. By means of the rod G, Fig. 240, draw a straight line to indicate a diameter of the nut. This line will serve as a guide for marking two points opposite to one another on the circumference, round which a circle has previously been traced with a graver. The points should be marked so deeply as to ensure that the drill does not displace itself in the initial stages of the drilling; with a little caution, and using a glass, very little difficulty will be experienced in ensuring that the points are in a right line. One of the two following methods may be employed for drilling the nut:
1. Prepare a brass block of the form shown at f p f′, Fig. 241, the space A being cut away, and the end p provided with large-headed screws, shown at v, v, in the plan. The two faces, f, f′, must be parallel to each other, and at right angles with the face p, a condition which can be easily satisfied by means of the lathe, the face f′, for example, being turned towards the headstock, and the dogs introduced into the space A; the opposite face f is then trued with the slide rest. In the vertical face a a make a round hole, through which a pointed center passes, being pressed forward by a spiral or other spring, and the point corresponding exactly with the line a a traced on the face of the brass; of course the axis of this center must be at right angles to the same line. A small block may be inserted within the space A to prevent any flexure of the arms.
An inspection of the figure will make clear the manner in which this little tool is to be used. Having fixed the nut on the face p by the screws v v, so that the two points on its circumference coincide with the line a a, the whole is placed in the drilling tool with the dogs pressing either on the upper external face or in the space A. After the block is fixed, ascertain by rotating the uprighting spindle that its point coincides in all positions with the top mark on the edge of the nut, and drill as usual. Drill one side, invert the block, and proceed in a similar manner to drill the other.
The little appliance above described might be simplified by being made of the form shown at E, which would require to be reversed when the second hole is about to be drilled.
519. To Polish the Inclined Faces of Ratchet Teeth. Set the ratchet in slow rotation by means of the foot-wheel, and bring a strip of spring covered with coarse rouge and oil against it from the side, resting the strip on the T-rest. In a very short time the teeth will be rounded and polished. This process is similar to that adopted at the present day for polishing the inclines of cylinder escape wheels in the lathe. The position of the polishing spring and its inclination must be determined upon by trial, so as to make sure that the entire surface of the tooth is acted on.
520. Another method is to make a small boxwood lap, and arrange it as shown at M, Fig. 242, so that, when caused to revolve on its axis, which may be more or less inclined, it is brought into contact with the ratchet wheel with its axis, as indicated by the figure. The teeth will cut into the wood, and trace out a helix, as seen at M′, and the lap, passing successively into the ratchet teeth, will cause it to revolve rapidly. When the groove is deep enough, apply some coarse polishing rouge to the surface of the drum; after a few rotations the faces will be found to be polished.
The arbor and lap may be arranged in either of two ways.
Mount the lap between the centers that carry the cutter in a wheel-cutting engine and support the barrel-arbor opposite to it in a vertical direction between the chuck and the bent arm or “gallows” used to fix a wheel while cutting its teeth.
A watchmaker who is not provided with this tool must chuck the lap in the lathe, then mount the barrel-arbor in such a carrier as is shown at p p, Fig. 242, and, resting its base on the T-rest, hold the ratchet against the lap, determining the most suitable height and inclination by trial; this, he will find, can be easily done.
521. To Polish the Circular Groove in the Ratchet. It takes a long time to accomplish this by using first, an iron polisher with oilstone dust, then one of copper with rouge and oil. The operation can be performed more expeditiously by using an iron runner, as shown at B, Fig. 243. The end is rounded to correspond with the groove; and the hole, which is indicated by dotted lines, should be large and funnel-shaped, so as to avoid contact with the corners of the winding square when a see-saw motion is given to B in the polishing.
The arbor being cemented to a chuck in a lathe, hold the end o, charged with oilstone dust or rouge, in the groove, and, while the arbor revolves, rotate the spindle B in the hand, at the same time giving it a see-saw motion as above mentioned. A very little practice will be required to do this.
522. Repairing a Barrel-Arbor. Cement the arbor a a, Fig. 244, to the lathe chuck, turn down the ratchet, removing its teeth and thus diminishing its diameter by about a third, as shown at n n; then reduce the thickness to a half, turning it down on the side next to the winding square, and continue this square down to the flat disc that remains, taking care that no shoulder is left at the angle between the two. The arbor is now in a condition to receive the new ratchet which has to be fitted.
Adjust a flat ratchet r r like those used on the barrel-arbor of a fusee watch, which must be of the thickness and diameter of the original ratchet, so that it exactly fits the winding square; turn a sink in it, as shown by the dotted line, to receive the disc already formed; and, if the hole fits the winding square freely but without play, and this square is carried down to the disc, the dust cap c c will maintain the ratchet in its position as effectually as though it formed one with the arbor.
By adopting the above method, which does not occupy much time, it is often possible to avoid making a new arbor when all but the ratchet is sound; and if this portion should again wear out, the necessary repair is still further simplified.
We are assured that arbors repaired in the above manner showed no signs of wear after fifteen years, except that the square in the ratchet was a trifle enlarged, though not sufficiently to interfere in any way with the efficiency; moreover, in modern watches, the winding square is generally long, so that the ratchet can be left somewhat thicker at the center and a corresponding sink cut in the under side of the dust cap to receive it.
523. To True a Barrel-Arbor that is Coned Inwards or too Large. Cement the arbor firmly to a chuck as shown at C, Fig. 245. With care it will be easy to make the part e run true. As a rule, but very little metal requires to be removed to make e cylindrical or conical in any desired direction, and it will generally be sufficient to finish by polishing with an iron polisher and oilstone dust or coarse rouge and oil. Use a narrow polisher that only bears on the end of e, giving it a double movement, straight forward and in a half circle towards one side; or else use a broader polisher, supporting it on the T-rest. By inclining this, the iron can be prevented from touching e, except near its extremity. It is unnecessary to add that when the arbor has been made cylindrical or coned in a given direction a suitable polisher, bearing on the entire length of e, can be used.