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Watch Repair - Making Small Tools

( Originally Published 1918 )



IN former times apprentices made the greater part of their own small tools, and it was very good practice in filing and turning to do so. The tools so made were generally of more lasting quality than modern bought ones. No one now thinks of making his own tweezers, screwdrivers, broaches, and turning arbors, because such things are purchased so cheaply and are so good. But the same cannot yet be said of all tool-shop productions.

Drills.—It is necessary occasionally to make a drill, the process being as follows : A piece of steel wire (a broken broach is good if softened) is filed flat on the end and held in a pin vice. It is rested on the edge of the anvil or stake, and " spread" cold with a light blow or two of a watch hammer, as at A (Fig. 54). B shows it spread. It is then shaped by a file like a finished as at C, hardened in oil, brightened with an emery buff or on an oilstone, and tempered to a pale straw for C ordinary work, or left hard if for tempered steel. A drill so small that it cools before reaching the oil is hardened by "flirting," as described under "the hardening of steel."

Taps.—To make a tap, take a piece of well softened steel wire, taper it gradually to just enter the hole of the screw plate ; work it in very carefully with plenty of oil until a full thread is cut for a sufficient distance, then lay it in a groove on the boxwood block and file three flats upon it, making it triangular for its whole length, slightly tapered all along and a little more tapered towards the extreme end, where the thread should just disappear. A tap should be hardened in oil and tempered to a full straw. Each flat is smoothed on the oil-stone to give sharp cutting edges. Finally the number of the screw-plate hole is filed in Roman characters on its back end. In small sizes triangular taps cut much more freely than square ones. This is a "taper tap." A "plug tap " has the full thread left right up to the end, and is to follow the taper tap when cutting a thread in a shallow hole in which the screw is required to reach to the bottom.

Punches.—A centre punch should be turned from good tool steel rod é in. thick, or from a large broken broach well softened. Its shank should be soft, but the point hardened in oil and left hard. Fig. 55 shows the shape. A gentle taper enables the exact position of the punch to be seen when placed on small work, and the sudden short taper at the point gives strength.

A pivot shoulder punch is for placing over a balance-staff coned pivot to drive on a roller or for other operations. It is made of square steel 1/8 in. square, and may be made from an old file handle. It has a hole drilled through near to one end, leaving the face thin. A pivot drill is then put through the centre into the big hole and chamfered out a little. The coned pivot operated upon passes through this small hole in the punch face, and the chamfered part rests upon the pivot shoulder and does not injure it. Fig. 56 shows one. These punches are left soft, so as not to mark the pivots.

Punches of all shapes in graduated sizes — flat-faced, round-faced, flat with central hole, etc.—can all be made from steel rod, turned up and drilled. The shanks of all should be left soft, and the faces only hardened and polished. No tempering is needed. The tops of punches where the hammer strikes them should be slightly rounded.

Screwdrivers are so cheap and good that ordinary ones are best bought, but a useful one for specially small screws—smaller than jewel screws—can be made from an ordinary needle, sharpened on the oilstone to a chisel edge, and soft soldered into a length of small brass bushing wire for a handle. Such a screwdriver is useful for turning the screws that fasten some white dials on from the front, and does not chip the enamel. To soft solder the needle in the brass, some killed acid will be wanted as a flux. Killed acid,is spirits of salt in which zinc cuttings have been dissolved until the acid will dissolve no more. A little acid is put in the hole, some is put on the needle, and the needle inserted in the hole. A small piece of tinman's solder is placed at the joint, and the whole held over the flame of a spirit lamp. When hot, the solder will run and flow in the hole, adhering where the acid has run. While hot, dip it in water and wash well to remove all traces of acid, which would otherwise rust the steel.

Many watchmakers use oil to prevent rusting after soft soldering. This is no good at all. The only safe method is to thoroughly wash in water and dry off quickly. Steel parts treated thus never rust at the joint or where the acid has been.

Countersinks.—A set of chisel countersinks for sinking the heads of square-headed screws is very useful. They should run from the jewel screw size to that of pillar screw heads.

A straight piece of steel wire is taken, and a hole drilled up one end to take a central pin of such a size as to enter the screw hole easily. It is then put in the lathe or turns, and a short length turned down to the required size of the sink it is to cut, as at A (Fig. 57). This is then filed to a thin chisel. edge like a screwdriver, and hardened and tempered as a drill. It is then sharpened well on the oilstone, and a truly filed tempered steel pin driven in the central hole and rounded up on the end smooth, as at B. The set may each have a brass ferrule driven on, as in the figure, or may be short lengths fitted to a drill stock, or may be made to fit a lathe chuck.

The usual set of circular countersinks sold are very good for work of such a size as to admit of their use. For making a delicate dot to start a drill, a small pointed chamfering tool is useful, and can be made from a piece of pinion wire or steel wire 1/8 in. thick and about 2 1/2 in. long. One end is turned down parallel and the point sharpened, as shown in Fig. 58 at A, by being rubbed down or filed to a triangular point having three flats and three. cutting edges. This is hardened in oil and left hard, and must be kept quite sharp for use.

A similar sized countersink or chamfering tool, with a semi-circular edge, sharpened like a round-bladed chisel, is useful for just taking the edge or burr off a pivot hole or other small hole.

Joint Pusher.—This is for pushing out joint Fig. 58 —Pointed pins. A piece of steel rod about half as thick chamfering Tool. again as the average large joint pin is set in a handle made of 3/16 in. round brass rod, by drilling up the rod and driving and soft soldering the steel into it. The steel is gently tapered down to a convenient site for joint pins, and the end is left fiat. The brass handle has a circular turned brass cap riveted on for applying pressure by hand.

The steel portion is hardened and tempered blue. The whole may be 4 in. long and of the proportions shown in Fig. 59.

The Oiler is to apply the watch oil to the pivots and other parts requiring it. It is made from a 4-in. piece of steel wire, spread like a drill at the blade, very thin and rounded on the edge. The handle can be turned into a ring for convenience. Fig. 6o shows one. The watch oil is kept in its original bottle and put out a drop or two at a time, for use, into an " oil cup " having a cover. The oiler blade is inserted into the oil cup and takes up a minute quantity of oil, which can be transferred to the pivot holes, etc., by just touching them. A drop or two from the original stock bottle is enough to oil a dozen watches.

A brass "blueing slip " is an oblong piece of thin brass sheet, about 1 1/4 in. X 5/8 in. To it is "hard soldered" an iron wire handle—iron, because it can be held in the fingers, heat not running up iron like brass. Fig. 61 shows the appliance. A row of graduated holes is drilled across the end to accommodate screws for blueing, a larger hole or two being behind them to take the pipes of hour hands so that the hand may lie flat on the brass. Another similar slip may be made with no holes, for blueing flat pieces of steel. This one may also have a groove filed across its centre, so that pieces of round steel wire will not roll off while heating.

To hard solder the handles on, silver solder is used, and borax and water rubbed to a paste is used as a flux. File the parts to fit; lay them on a block of pumice stone in position, having boraxed the surfaces ; lay a piece of silver solder along the join, and blow to a good red heat. Warm very gently at first, as the borax will boil up and may displace the parts ; then raise gradually to running heat, when the solder will flow in.

Brass spelter may also be used for hard soldering, in the same way as silver solder; but it rims at a greater heat, and does not flow so nicely.

A pair of brass tweezers, for handling the polished steel parts of new watches, are very useful, and may be made from two pieces of thin brass sheet thinned by filing and riveted together. Before riveting they should be well hardened by hammering. Brass tweezers, being soft, will require constant filing up of the points to keep them in good condition. Tweezers that have become slightly round on the edges with wear are apt to shoot off small screws and other parts.



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