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Watch Repair - Motion Work, Hands, And Dials

( Originally Published 1918 )



Motion Work.—The ordinary motion work (Fig. 164) consists of a steel cannon pinion, A, so-called from its shape, a minute wheel, B, and pinion, C, generally of brass, and a brass hour wheel, D, revolving upon the pipe of the cannon pinion. The teeth of these wheels are so proportioned that the hour wheel makes one revolution to twelve of the cannon pinion.

Rough cannon pinions are bought, and require fitting to the centre arbor; the outside has to be turned to fit the hour wheel, and the top cut to length or squared to fit the minute hand. Finally, the "snap" has to be made. Rough hour wheels require broaching out to fit on the cannon pinion, turning to revolve freely under the dial with a little play, and turning to fit the hour hand. A rough minute wheel and pinion has only to be broached out to fit upon its stud, and the pinion reduced in height to be quite free of the dial.

Motion wheels are often lost, and to some workmen it is more or less a puzzle to find out the right number of teeth for the new wheel.

The usual trains found in key-wind watches and keyless Genevas are as under :

Cannon pinion. Minute wheel. Minute pinion. Hour wheel

10 30 8 32
8 32 10 30
10 40 12 36
12 46 14 42

Modern keyless English levers generally have cannon pinion 14, minute wheel 28, minute pinion 8, hour wheel 48 ; and the minute wheel is of steel for strength, as the hands are set through it.

Any other train can be calculated, remembering that the minute wheel and hour wheel multiplied together and divided by the cannon pinion and minute pinion must = 12.

An English centre seconds motion train is generally cannon pinion and minute wheel 28, minute pinion 6, hour wheel 72, or minute pinion 7, and hour wheel 84.

Tightening the Hands.—A cannon pinion is often loose upon its arbor and turns too easily. Some are snapped on by having a hollow filed in one side and a centre-punch mark in its thinnest place. This makes a bulged place inside, which springs into a slight groove turned in the centre arbor. To tighten one of these, punch the snap, resting the cannon pinion on boxwood. Some have circular snaps. A groove is turned round the cannon pinion and the thin bottom is burnished in. To tighten one of these, hold it in a split chuck in the lathe and reburnish the bottom of the groove. If these methods fail, the arbor may have some rings made round it with cutting nippers. Or if the pinion has a square for the minute hand to fit on, two opposite sides of the square may have a centre-punch mark deeply made on the outside. A cannon pinion that does not turn upon its arbor when the hands are set may be tightened by inserting a hair from the watch brush and pushing the pinion on tight.

A loose set-hands arbor, going through a hollow centre pinion, may be tightened by ringing it with cutting nippers, or by rolling it between two files under pressure. Never hammer them to tighten; it only knocks them out of truth.

An hour wheel that rocks badly upon the cannon pinion can have a new pipe put in very easily by means of a watch lathe, holding the wheel in a step chuck and turning the pipe clean out. A new pipe is turned from clock stopping wire and riveted in.

An hour wheel that has too much shake under the dial may have one or two paper washers placed over it; or a thin washer made of metal foil curled up at the edges to form a light spring and keep the wheel down.

The motion work in some cheap watches is very roughly made, and the teeth have burrs left on them, making the depths tight. Such wheels may be brushed through the teeth with a brass wire brush.

Fitting Hands.—The hands are more important than many people think, and badly fitted or faulty hands probably stop more watches than anything else. The hour hand should push tightly on to the hour-wheel pipe. If the wheel pipe is thin, pushing on the hand sometimes tightens the wheel upon the cannon pinion. The remedy for this is to take the hour wheel out of the watch and put the hand on it, then to just turn a broach round inside to ease it. Some hour hands have thick sockets that rub against the dial. These require thinning down in the turns. To open out an hour hand that will not quite go on the hour-wheel pipe, hold it in a pair of hand tongs, like Fig. 104, p. 91, and file it out with a rat-tail file. Do not use a broach. Or it is sometimes advisable to turn the hour-wheel pipe to fit the hand. For this purpose, put it on an arbor in the turns.

A minute hand that fits on a square cannon pinion requires filing out to fit the pinion. Hold it in the hand tongs, and use a square file that cuts on all four sides. Do not attempt to file the sides of the square hole, but file its angles one stroke in each, round and round the hole. This keeps it square. A minute hand that has a round hole should, if large enough to admit of it, be filed out, and not broached, as broaching leaves a burr. A minute hand centre boss that is too thick should not be filed, but always reduced by turning. This keeps all surfaces true and flat.

A seconds hand requires broaching to fit on its pivot. If the pipe is too long, shorten it by laying it upon a piece of boxwood, pipe upwards, and placing a piece of thin brass over it so that the pipe comes through a small hole in the brass and projects upwards. File off the projecting part. To remove the burr, put the hand on a pivot broach and file it off with a pivot file, resting the pipe in a filing groove in the boxwood. A pipe may be reduced in thickness by sticking the hand tightly on a pivot broach and filing the pipe with a pivot file on the filing block, manipulating the broach as if it were a pin vice.

All the hands of a watch should be quite free of the dial, the glass, and each other. The hour hand must always have a little play, showing that it is quite free. A fragment of tissue paper shut under the glass over the minute hand centre will show if the hand touches, or a drop of oil or red-stuff on the hand will mark the glass.

Set-hand Arbors.—A new set-hand arbor in a Geneva watch is fitted by filing in the pin vice.

Rough arbors are bought from the makers with the square formed and the arbor rough turned, the whole being hardened and tempered. Pick out one with a square the same size as the winding square. Hold it by the square in a pin vice, and with a fine file reduce the arbor to a very gradual taper to fit the centre pinion. Very careful filing is necessary towards the end of the operation, and for the final fitting a pivot file should be used. When fitted to the centre pinion a good tight fit, reduce the projecting end to fit the cannon pinion, a good driving-on fit. Then cut off to length, round up, and burnish the end. Reduce the square to length, and file off its four edges a little bevelled, smooth and burnish it in a lathe or screw-head tool.

Some old English 3/4-plate watches have set-hand arbors made in one piece with the cannon pinion, and the square at the back pinned through. Often the arbors are broken off where drilled through. In such a case it is best to put the cannon pinion in a split chuck, turn the arbor off, turn a true drilling centre, and drill the pinion right through. Then fit a Geneva set-hand arbor of the ordinary pattern.

Some difficulty is sometimes experienced in getting the small pin out of these loose set-squares. If a flatted needle is held in a pin vice and used as a pusher, the square is liable to turn round and cause the needle to scratch the watch plate. To do it safely, hold the movement by the cannon pinion, either by means of a pair of cutting nippers and its square or by holding its body in a pin vice. The pin can then be pushed through firmly with no fear of the arbor turning round.

To polish up such a loose set-square, file a taper steel pin, drive the square on, and smooth and burnish it in a screw-head tool or split chuck in a lathe, holding it by the pin.

Enamel Dials.—White enamel dials are subject to many accidents. A crack can only be left alone. A piece chipped out may be stuck in again neatly with gum, or, better still, " coaguline" or "seccotine" cement. A piece chipped out and lost can be filled in with the special white dial cement sold for the purpose. Run a little of this on warm, like sealing-wax, and when cold file it off flat. Then warm over a flame to just "gloss" it. A loose seconds piece is cemented in with this cement. Scrape the piece clean on its edges, and also the dial edges inside. Hold the dial in pliers and warm it in the spirit-lamp flame, run on the white wax, as you would sealing-wax, and place the seconds piece in position. Hold the dial level, and again warm it until the cement is seen to run well. Finally, file off the surplus cement flat.

A soldered seconds may be re-soldered by scraping the edges clean, applying the acid, and laying the seconds piece in place. Cut off small pieces of solder and lay over the join at short intervals all round. Hold the dial with pliers over the lamp flame until the solder runs. Let cool slowly and wash well.

Any brown discoloration that forms on the dial face by heating may be removed by washing or by a peg point and rubbing.

A dial hole is opened by chamfering a little with a small emery stick (sold on purpose) with a cone-shaped end, and then filing with a rat-tail file and turps. Great care has to be taken not to let the file go so far in as to block, or the dial will crack. The outer edges of a dial may be reduced by filing and turps, or with coarse emery sticks. The back of a dial may be hollowed at one spot to free some of the motion work by rubbing round and round with one of the small circular emery sticks kept moist with water.

Sometimes the feet break off. To replace one, scrape off the back enamel with a graver to lay bare a space about 3/16 in. round. Make a new foot from copper wire, and silver solder it on to a round base 3/16 in. diameter, as in Fig. 165. Soft solder this on to the dial.

The figures of enamel dials are burnt in, and cannot be rubbed off by ordinary means ; but names are sometimes added after-wards, in which case they can be removed in a moment by a peg and spirit of wine. A burnt-in name may be removed by using a polishing paste of diamantine and water used on a flat-ended peg. Half an hour's patient rubbing will remove the name and leave a polished surface.

Metal Dials.—Silver dials go a very bad colour in wear. If they have gold raised figures, they may be much improved by washing in soda and hot soap and water and drying in boxwood dust, the gold figures being previously buffed over with a rouge-on-leather buff. This process is apt to remove any painted figures there may be. To restore such a painted dial as new involves bleaching and repainting, which is dial-maker's work.

Gold or silver-gilt dials may be washed in the same way as silver ones. For restoring as new, send them to a dial-maker.

Feet may be put on gold or silver dials by soft soldering. Some gold and silver dials are snapped on by a turned-down edge. Such dials often get loose. To tighten them, lay face down on flat wood with paper between, and burnish the edge a little inwards by hand with a wetted oval burnisher.

To open holes in metal dials, never use a broach ; do it all by filing, the dial being held face upwards.

A finger mark may be taken off a new gold dial by clean tissue paper twisted up into a little mop and moistened, using it in the same direction as the engine turned marks on the dial face. Both gold and silver dials, when new, have very delicate surfaces, and should always be handled with tissue paper. The slightest touch of the finger-tip marks them badly. Great care should also be taken in removing the hands not to scratch them, as scratches can only be removed by re-engine-turning the surface.

General Remarks.—Steel hands are sometimes blue and sometimes red. A red hand, however, can always be blued by placing it on a blueing slip and heating. Thus, if a blue hour hand is wanted to match a minute hand, and only a red one can be found to fit, then blue it to match ; or if an hour hand is wanted to match a red minute hand, and only a blue one can be found, then blue the minute hand to match it.

An enamelled dial that is thick and prevents the bezel shutting down properly, or that leaves no hand room, may be thinned down on the back with a coarse emery stick until the copper nearly shows bare.

Never leave much white dial cement on the back of an enamel dial round the. seconds piece. It breaks away and adheres to the oil round the pivots in the lower plate. Oil dissolves it and forms a sticky compound like glue, effectually sticking the pivots in their holes and stopping the watch.

A seconds piece that is cut out to show the phases of the moon, as in some calendar watches, has a loose centre piece, and a new one can, if necessary, be filed up with a file and turps from the centre of an ordinary seconds dial.

"Up and down" mechanism is sometimes found in good fusee watches to show when the watch is wound up or run down. A small pinion is driven on to the bottom fusee pivot, and works an " up and down wheel," which runs on a fixed stud like a minute wheel. This wheel carries the indicator hand.

Up and down mechanism is occasionally seen in going-barrel watches, but involves great complication and multiplication of parts.



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