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Watch Repair - Depths, Trains Wheels, Etc.

( Originally Published 1918 )



Depths.—The power of the mainspring is transmitted to the escapement through a train of wheels and pinions. To transmit the power evenly and with as little friction as possible the teeth are accurately cut to special curves. The care bestowed by the makers upon the form of the wheel teeth would be thrown away if the wheels did not engage with the pinions to the right depth. A wheel and pinion action is termed a "depth." When they are too close together the depth is said to be " too deep ; " when too far apart it is " too shallow." In faulty watches there are thus deep depths and shallow depths. A deep depth causes waste of power and binding, the teeth of the wheel having little or no shake or freedom between the pinion leaves. A shallow depth causes friction and rapid wear of the teeth and pinion leaves. In a much shake between the teeth.

Fig. 87 shows roughly the construction of wheel teeth and pinion leaves. The acting diameter of the wheel is its " pitch diameter," and is shown by a dotted circle called the " pitch circle." Up to this point the flanks of the teeth are radial lines from the wheel centre. Beyond this the teeth are curved to a point. The flanks of the pinion leaves are also radial lines up to its pitch circle, and beyond that are finished off with a semicircle. In a correct depth the pitch circles of wheel and pinion are in contact with one another, as in the figure. The broadest part of the wheel tooth acts upon the broadest part of the pinion leaf. In this position the wheel teeth will have a little shake between the pinion leaves.

Some of the depths in watches can be easily seen, such as the barrel and centre pinion, or fusee and centre pinion, or the centre and third pinion of an English watch. Others can only be tried by putting the two wheels together between the plates. The pinion is held firm while the shake of the wheel teeth is observed, or felt. Some watches have sight holes drilled in the plates to enable all the depths to be seen; but in most some of the depths can only be felt.

A depth that is so deep as to have no shake at all will stop the watch, and must be corrected. A very shallow depth will not often stop a watch, but wastes the power and renders it liable to stop from the slightest cause.

When the pivots run in brass holes a depth can be corrected by drawing one pivot hole, that next to the pinion being the best. A hole is drawn by broaching it out larger and pressing the broach to one side firmly with the finger-tip as it is turned, causing it to cut on one side faster than the other, and draw the hole oval in the desired direction, as in Fig. 88. It is then broached out round and "bushed".

When the pivot holes are jewelled, a deep depth can be corrected by topping the wheel teeth in a" wheel rounding-up tool." This is a kind of automatic wheel-cutting engine, and extremely useful to a watch repairer. In effect it makes the wheel a little smaller. Topping a wheel with a file is no good at all. A shallow depth, when the holes are jewelled, can be sometimes improved by stretching the wheel rim by gentle hammering or burnishing; but this makes a poor job. The only real remedy is a new wheel.

With constant wear, pinion leaves get cut by the wheel teeth into holes or hollows. These hollows hold the dirt and stop the watch, besides causing great friction while the watch goes. It might be thought that when two metals work together such as brass and steel, as in a brass wheel and a steel pinion! or a steel pivot in a brass hole, that the softer of the two would wear the most. It is the contrary that always happens. The harder metal wears more quickly. This is because wear is caused by dirt, dust, or grit getting between the surfaces. This imbeds itself in the softer metal, and converts it into a kind of grinding-mill, which cuts the harder metal. Thus pinion leaves get worn out before the wheel teeth, steel pivots wear before the brass holes, and brass scape-wheel teeth cut hard steel pallets. It follows that watches wear much longer if kept clean.

A worn pinion cannot be repaired. Sometimes, where there is room in the watch, the wheel which runs with it can be raised or lowered so as to act on a fresh and unworn part of the pinion, as in Fig. 89, which shows a section of such a wheel. The doming stake can be used. The wheel is placed in the hollow, with the pinion passing, through the central hole, and a punch is placed over it, having a central hole to accommodate the arbor. A tap or two will spring the wheel concave. This process sometimes leaves the wheel true and sometimes not. If not, it must be run in a pair of calipers, or in the turns, and the high or low spot noted. Then lay the wheel on a piece of boxwood, and a tap with a small flat punch on the centre of one arm will raise the wheel rim at that point. A few taps and trials will soon get it true. Any untrue wheel can be treated in this manner.

Pivots.—Pivots often get worn, ribbed, and cut into channels like Fig. 90. These must be polished down in turns or lathe, and the holes which then would be too large must be bushes,

To smooth and polish a pivot, put it in a split chuck in the lathe, holding it by the other end of the arbor, or, if there is no arbor to grip, hold the wheel in a step chuck. If neither of these methods can be used, the wheel must be cemented by shellac to a small brass chuck. Warm the chuck in the spirit lamp and run shellac upon it. The chuck face should be flat with a central hole. Lay the wheel upon the chuck face and again warm until the shellac runs. When partially set, screw the chuck in the lathe. Now hold the lamp so that the flame warms the chuck and softens the shellac, and run the lathe slowly. When softened, hold a peg point to the arbor close up to the pinion face or wheel seating, in the angle. Touch it very lightly and the peg point will run it true. Continue to revolve the lathe and apply the peg point until the shellac sets. Fig. 91 shows what is meant. It is possible to hold nearly every job in this way in a watch lathe, and be independent of chucks. Things held thus run perfectly true, which is not always the case with split chucks. The whole process of cementing and running true only occupies a minute, though it takes many to describe.

When true in the lathe, take a strip of flat steel about 6 in. long and 1/8 in. wide ; file it flat on one side and slightly bevel one edge to the section shown in Fig. 92. This is a polisher. Mix up some oilstone dust and oil to a paste on a polishing stake. Apply some to the polisher face, and while the lathe is running polish or grind the pivot down, using the polisher as a file with light pressure, as in Fig. 92. Care must be taken to hold the polisher level, or the pivot will be ground down tapered instead of straight. A very little of this treatment will smooth the pivot. Too much will reduce it to nothing. When smooth, clean off the oilstone dust from the pivot with pith and cleanse the polisher, giving it a fresh surface with a smooth pillar file. Recharge it with red-stuff and oil mixed to a paste on another polishing stake. Use in the same manner for a few minutes, revolving the lathe fairly fast. This will polish it. Keep the mixed and unmixed red-stuff very carefully covered up and free from dust.

If shellaced on a chuck, the wheel can be warmed off and the remaining shellac boiled out in a little spirit in a spoon held over the lamp.

In the turns, a ferrule must be affixed to the pinion, and a back runner (A, Fig. 93) with a centre near its top edge used.

A polishing bad (B) is a brass runner turned to the shape shown and having slight hollows cut around its edge for various sized pivots to lie in. Select a hollow that takes half the pivot in depth. Adjust the runners and pinion as shown in the figure, and use the polisher as before described. On the downward stroke of the bow the polisher must go forward, on the up stroke of the bow the polisher comes back as in pin filing. Never forget to apply a little oil to the back centre. After polishing in this manner a few minutes, reverse the motion for a few strokes, letting the polisher come forward as the bow comes down. This mixes up the polishing paste.

Oilstone dust should be used rather thin and " sloppy." Red-stuff should be rather a stiff paste, and a very little put on the polisher. The art of producing a good polish on a pivot is to move the polisher about upon the pivot, not keeping it always up to the shoulder, to use long strokes of the bow (or in a lathe rapid revolution) and long strokes of the polisher.

A final gloss can be put on a pivot by cutting a peg flat on one side and applying red-stuff, using that as a polisher for a moment with a high speed.

Turning Pinions.—When a new pinion is required, a rough one (Fig. 94) is purchased from the tool shop. This is hardened and tempered ready, and the leaves are cut and polished. It is also centred truly ready for turning.

First put the old pinion in lathe or turns, turn off the riveted face of the pinion, and knock the wheel off by punching the pinion through it. Turn the new pinion body (leaf portion) down to the correct length by using a good speed, a sharp graver, and cutting with the point only. The ends of the leaves can be faced well enough for most jobs by a polisher held as in Fig. 95, using first oilstone dust and then red-stuff as before described. If a perfect flat face is required, as in new work, the centre of the leaves must be turned hollow or "cupped" a little, to leave no root in the shoulder, and a square or bevel edged polishing lap brought up to it in a watch lathe. A polishing accessory is made to fit in the hand rest of the lathe, by means of which these laps can be accurately adjusted. A seat for the wheel is then turned so that the wheel drives on tight. It must on no account be an easy fit. The points of the leaves should stand up above the surface of the wheel for riveting over and be turned hollow inside, leaving a circle of points like a crown, as in Fig. 96. The pinion arbor should be turned down, leaving a slight square shoulder, as at A, Fig. 97, for the polisher to go against when polishing it. The arbor should be finished and polished before turning the pivots. A straight pivot should have a clean square shoulder, as at A, Fig. 98 ; not a " root," as at B. Turn the pivot as smooth and true as possible, then smooth it with oilstone dust. Before polishing, sharpen the graver and place as in Fig. 99, to give a final clean cut in the shoulder just one sweep down of the bow in the turns or two or three revolutions of a lathe.

Turn the bottom pivot first, and, if a jewel hole, fit it to the hole by reducing with oilstone dust until it just goes in and sticks. Then polish, and it will fit properly. If a brass hole, leave the pivot a shade large and open the hole to fit. When the bottom pivot is turned and the wheel and pinion got to the correct height, the total length of the pinion can be measured and the top pivot turned. Take a piece of thick brass wire, file it flat on both ends, and fit it accurately so that it will stand up on the bottom plate or jewel hole and have a correct end-shake under the top plate or hole. This will then be a gauge for the total length of the pinion, and can be measured over all with vernier gauge or douzième gauge.

Round up the ends of the pivots by a pivot file and burnish them. Finally rivet the wheel on. Put the pinion in a steel stake in the vice jaws. Press or punch the wheel on to its seating, and with a flat-ended steel punch rivet the points of the leaves well into the wheel. As a finish, turn the riveted surface clean.

Using a lathe, the pinion body can be held in a split chuck for reducing and facing, and also for turning the wheel seating, turning and polishing the arbor and the pivots. Or it may be shellaced into a chuck like Fig. 100. This chuck has a cone hollow, and is filled with shellac. This is warmed and the pinion pressed in until its lower end rests in the bottom of the cone. The shellac is built up round it and the pinion " run " true with a peg.

A cone shellac chuck for " running " true has to be warmed as it revolves in the lathe, and the ordinary form of chuck carries the heat away very much to the lathe headstock. This difficulty can be got over by drilling two large holes through the chuck at right angles to and through each other, and broaching them out as shown in Fig. 100. The chuck end that is heated is then only joined to the lathe by four slender strips of brass, and the heat is retained better.

These cone chucks ensure the perfect truth of both ends of the pinion.

If preferred, the entire pinion can be turned between dead centres, using a loose pulley runner and a carrier.

In the turns, a ferrule is affixed and the pinion placed between large centres to turn the body, face it, and turn the wheel seating. The arbor is turned and a rough pivot formed on its end, to rest in the polishing bed while polishing the arbor, as in Fig. 93, p. 86. It is cut to length by turning through with light cuts and a very sharp graver, like Fig. 101. This will leave almost a point. The centre is "run " by a pivot file, as in Fig. 102, A showing the end of the " running arbor. This forms a true turning centre. For turning the pivots a back centre (A, Fig. 93) is used. The front runner is triangular with a minute centre (made with pointed chamfering tool) at each corner, as near the edge as possible, like Fig. 101. They are polished as shown in Fig. 93.

Bushing Holes.—To bush a pivot hole, " bouchons " like Fig. 103 are used. These are small lengths of hard brass wire, each end of which is turned down and drilled up its centre. Select one with a central hole that will just stick on the pivot. Hold it in a pin vice and taper it very slightly at the point. Open the pivot hole by broaching from the inside surface of the plate or bar, until the bouchon goes in tight half-way. Then insert it and break it off where half cut through. File the projecting end flat, place a flat punch upon it and tap it quite in. Open it with a broach to take the pivot nicely, taking care to broach the hole upright. The inside surface may be stoned off level, or it may be turned in the mandrel. The outside surface where the oil cup comes may be chamfered out or turned. In each case turning makes the best job.

The bottom centre wheel hole in a full-plate watch, or either centre hole in a Geneva, must have a specially turned bush. A piece of clock bushing wire is sawn off about twice as long as the watch plate is thick. It is held in a pair of hand fitting tongs (Fig. 104) and broached out nearly to go on the pivot, placed on a turning arbor in the turns, and made true at each end, reduced in diameter and tapered. The pivot hole is then broached out to receive it. The bush must be turned to the exact length to rivet in, each face being turned a little hollow to leave an edge for riveting over. The hole is very slightly chamfered, and the bush riveted in with a flat punch on a flat stake. It is finally turned off on both sides flush and clean, and opened out to fit the pivot.

The bottom centre pivot of a full-plate watch is often so worn that turning it true and polishing will reduce it to a smaller diameter than the part where the cannon pinion fits on. In such a case turn the pivot down level. Make a steel collar and soft solder it on, afterwards forming a new pivot. The hole can then be opened out larger to fit. The steel collar is conveniently made by turning down a portion of an old cannon pinion, and is then ready hardened and tempered. The collar forms the new pivot.

Similarly, a top fusee pivot is often worn smaller than the winding square. In this case the pivot must be turned down and polished and the square reduced, the set-hands square being also reduced to match it and fit the same key.

A "hollow" fusee is one in which the pivot is sunk in a hollow and cannot be got at for turning without taking the fusee to pieces. In these fusees tl.e body can be entirely removed by taking out the three screws that hold the internal ratchet on.

A top fusee hole in a full plate requires a bush specially turned from bushing wire as a centre wheel. Turn it to the shape shown in Fig. 10)5. The bush rests upon the shoulder, and is riveted on the under side as shown in the section. A "setting" held by three screws, as in many 3/4 plate watches, may be bushed as described for a centre wheel.

Any bent wheels should be trued by a punch on boxwood, as on p. 84. If they touch their sinks in the watch plate, put the plate in the mandrel and turn the sinks out.

Wheel Teeth.—Broken teeth are put in by slotting and soft solder. The root is filed out flat, as A, Fig. 106, slotted with a slitting file, as at B. To widen the slot and square its sides, the teeth on the edge of the file can be smoothed off on an oilstone for half an inch at one end, so as only to let the file cut on the sides. A piece of brass pin wire is filed flat on two opposite sides, fitted tight in the slot, and cut off as at C. Wheel and wire are then laid on a blueing slip, a little solution applied to the slot and pin, and a minute piece of solder laid on it. All is then warmed over the flame until the solder runs in. After well washing, file off as at D, clear out the solder between the teeth, and shape up as at E. Flat both sides by laying the wheel on cork and using a fine sharp file. Finish with a buff and a rouge buff.

Several teeth can be put in a wheel by filing out and fitting a piece, as in Fig. 107, but in such cases a new wheel is best.

New Pivots.—Broken pivots are replaced by drilling, fitting a piece of tempered steel like a plug, and forming a new pivot.

A top centre pivot, like Fig, 108, A, is best put in by turning off the arbor and drilling the pinion body itself with a large hole, forming arbor and pivot on the new piece of steel, as at B. A third pivot is replaced as at C. A shallow pinion and thin arbor like D is repaired by drilling right through and putting new arbor and both pivots. A broken pallet staff pivot in an English watch requires a new staff complete.

In a lathe nothing is simpler than putting in pivots. Where possible the pinion body (preferred) or arbor is held in a split chuck ; or the wheel is held in a step chuck or by shellac. The hand rest is brought up and a centre for drilling turned, like Fig. 109. A very sharp graver and a good light are necessary, to see that no "pip" is left in the bottom of the hole. A drill (hardened and not tempered) well sharpened is put in the drill holder and lubricated with turps. Slow revolution and good pressure will cut almost any pinion. The moment the drill stops cutting, resharpen it. If it cannot be made to cut, blue the pinion in the spirit lamp and remove the blue by dipping for a moment in strong spirits of salt and well washing. It will then drill all right. Drill at least two or three diameters deep. Then peg the hole clean. Take a needle, let down to a blue temper, and in the pin vice file it down tapered (nearly straight) to fit the hole tightly half in. Fit it in. Cut it off and file flat on the end, as at A, Fig. 110, and hammer it in. Then put again in the lathe and turn, fit it to the hole and polish, finally burnishing the end.

In the turns there is more trouble. Fit up the turns as in Fig. III. The back pivot runs in a centre, and the drill is held in a central hole in a brass runner. The drilling centre is made by resting the pinion on a stake and chamfering with a pointed tool in its exact centre. If not quite correct it can be drawn and chamfered deeper. Then drill, leaving the brass runner loose and keeping the pressure up by hand. Fit the steel plug, and file a turning centre upon it by hand. Try in the turns for truth, and draw the centre by filing on one side until the pinion and wheel run true. Then turn and polish the pivot. A pivot end is rounded up and burnished in the turns by means of a lantern runner, as in Fig. 112. These are made of brass. A slender back pivot may be put through a "safety back centre," like Fig. 113 ; here the pivot shoulder takes the thrust. A centre like this is always used with a coned pivot.

Jewel Holes.—Jewel holes often crack. A cracked hole will cut a pivot and cause friction ; it should be replaced with a new one. Some jewel holes are set in the plate, lying in small circular sinks, and a thin brass edge is burnished over to hold them in, like Fig. 114, at A. When such a hole is broken it can be pushed out with a flat-ended peg and a hammer. This generally raises the thin brass edge; but if not, it can be raised by running a centre-punch point round inside with a circular motion. Then select an unset jewel hole to fit the sink and pivot, and burnish the brass edge over it again with the centre-punch point held in the fingers, working it lightly round and round, as in Fig. 115.

A jewel hole that is fixed in a brass setting and held by two screws had better be fitted by a watch jeweller. Watch jewelling is a trade by itself, and very few ordinary repairers can do a jewelling job even passably; none can do it well.

English jewelling fitted with endstones can only be re-placed by keeping a stock of set jewel holes and selecting one that fits the sink and the pivot. Even then the thickness is often wrong. This jewelling also is best sent to a jeweller for repair. An endstone with a crack across or a centre " pip" cut by the pivot end must be replaced.

A Geneva endstone set in a small brass slip, when broken, can be replaced by fitting a loose one. Chamfer out the old setting with a circular chamfer and select a loose endstone that lies in the hollow with its surface level with the brass slip. A similar method can be followed in the case of an English set endstone, but is not so good as a new setting and stone.

An English endstone slip, fitting in a dovetail groove in a potance, is replaced by filing up and fitting a new brass slip.

Such slips are purchased in the rough with stones set in them. First flat the surface of the slip level with the endstone, then bevel and taper its sides, reducing the width gradually until the slip goes in its groove tight with the endstone central. Then cut off and trim the ends.

A broken centre wheel jewel hole or fusee hole is expensive to replace, and often is best broached out and bushed with brass. Occasionally, also, in a cheap watch a third or fourth jewel hole may be filled up with brass and re-drilled. In this case, fill up with brass, rivet well in, and smooth off by stoning or turning level. Then put the frame together, centre it in the mandrel by the other hole, and mark the hole to be drilled by catching the centre of revolution with a sharp graver point. When marked, hold a pivot drill in a drillstock in the hand and drill it through while running in the mandrel. If preferred, an "uprighting tool" can be used instead, but is not much better.

As before remarked, repairers cannot do jewelling properly, but many may like to try. The jewelling cutters and appliances sold with watch lathes are more ornamental than practical. The methods of the watch jeweller are better, and require less in the way of apparatus. The stones themselves are flatted by cementing to a brass disc and grinding with diamond powder on a copper lap running in the lathe. When one side is flat the stone or stones are reversed, and the other sides flatted and reduced to the correct thickness.

They are drilled by centring them separately in the lathe with shellac and using a diamond turning tool to cut a central sink. Then they are perforated with a diamond drill kept moist, or by a steel wire and diamond powder. The interior of the hole is polished with the finest diamond powder on a copper wire with extremely rapid motion. A jeweller's lathe has a foot wheel about 30 in. diameter, and a mandrel pulley of only r in. or ri in., driving with a cotton band—a mere thread—and revolving the foot wheel as fast as possible. The speed thus obtained is very high, being several hundred revolutions per second. The outside edge of the stone and the angles of the hole itself are turned out with a diamond tool.

To set holes in brass settings, jewellers screw a short length of brass rod in the lathe mandrel and drill its centre, turn out a sink to take the hole, turn the thin outer edge, insert the stone, and burnish it in ; then cut the set hole off. It is then reversed and shellaced on the chuck and the other side of the setting turned. A jewel hole is accurately centred by warming the shellac as the lathe runs and running true with a peg point, as described on p. 85. To see if it is absolutely true, a peg point is inserted in the hole and rested on the hand rest. As the lathe revolves, any want of truth is shown by wobbling of the peg end, A. If true, A will be motionless.

The hand rest is used throughout, and cutters formed from the tail ends of old files like those shown in Fig. 117. These cutters lie nice and flat on the hand rest, and are generally handy. Their handles may be wound with string and cemented' with sealing wax.

All sinks for jewelling and screw heads are done in the same manner by shellacing on to a chuck and by these hand tools.

By using these methods a repairer may sink jewelling to decrease endshake, and may perhaps manage other details, but cannot expect to be able to do the entire process of watch jewelling.

Frames, Screws, etc.—In English full-plate watches the top plate is generally pinned on. Sometimes the pin holes burst through the pillars or the pillars split. It is then best to flat the pillar top and drill and tap it, fitting an ordinary pillar screw.

A cock or other screw, broken in its hole, is often difficult to remove. First try two graver points to turn the broken tap out, as in Fig. r 18. Two points used thus relieve the screw of the friction against the sides of the hole. If nothing can be done in this way, it must be punched out from behind with a flat-ended hard steel punch that fits the hole. One hard blow, with the plate resting on a good stake, should drive it out.

The fitting of new screws is an important part of watch repairing. For Geneva work generally " Progress " finished screws are invaluable. They are purchasable in sets of half-dozen or one dozen of each size and kind. A box of these enables any screw for a Geneva watch to be picked out and put straight in. American screws are also purchasable for American watches, and save a great deal of time and trouble.

For English watches and some others of special make soft unfinished screws are bought. These require hardening and tempering, shortening to the correct length, and the heads reducing as required. But occasionally, with the best possible stock of screws, one will have to be made. This is easily done by putting a piece of steel wire in a split chuck, turning down the tap portion, and threading it in a screw plate. It is then reversed and held by the tapped portion while the head is turned and cut to length. Very small screws for hairspring studs, etc., and " shoulder " screws are the ones that most frequently have to be made thus.

Cap studs for English full-plate watches are bought in the rough, like Fig. 119, A, and require cutting to length and marking for the slot. This is then cut with a slitting file and the top end burnished in the lathe, as at B.

Screws are finished in three ways. They may be polished bright, or they may be heated on a blueing slip to a "red " or a " blue." In fitting from " Progress " finished screws, it should be remembered that a "red "screw can always be blued if necessary by simply heating it.

To polish screw heads, hold them in a split chuck and rest a fine file on the roller -T rest; follow this with a 3/0 emery buff. Then smooth with oilstone dust and polish with red-stuff. For common jobbing a "burnished" head is good enough. After using the 3/0 emery buff, apply a flat burnisher with good pressure and rapid revolution of the lathe. A burnisher is sharpened by rubbing it crossways with a fine emery buff.

For a bright finish this surface is good enough for jobbing, and does for screw heads, studs, winding and set-hand squares, etc. But a burnished surface is a false one, and will not blue. For blued or red screws the surface, for common jobbing, may be left from the 3/0 buff. For better work the screws must be polished before blueing.

Loose pillars in a watch frame should be riveted tight by resting their tops on boxwood and using a round-faced punch. If the pillar tops are rested on a steel or brass stake they will be bruised, and the endshakes of all the wheels will be found to be closed up.



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