If it is a train which requires 16,200, we then have to get the spring of such a strength that it will make 270 vibrations per minute; but it is best to count every alternate vibration, making the counting 135 per minute for the 16,200 train. If it goes a little over or under this number move the tweezers a little along the spring till you find the exact place where the number is correct; this is just the place to pin in the stud, and the watch will be to time. With the 16,200 train the watch beats 4 1/2 times per second; but some of the old-fashioned levers and Genevas beat only 4 per second; this, of course, can be counted by taking every alternate beat until you get 120 per minute. Those who follow this method will be able to set the spring and return it at once ready timed.
This is effected by grinding the spring down. Remove the spring from the collet, and place it upon a piece of pivot wood cut to fit the centre coil. A piece of soft steel wire, flattened so as to pass freely between the coils, and armed with a little pulverised oil-stone and oil, will serve as your grinder, and with it you may soon reduce the strength of the spring. Your operations will, of course, be confined to the centre coil, for no other part of the spring will rest sufficiently against the wood to enable you to grind it, but this will generally suffice. The effect will be more rapid than one would suppose, therefore you will watch carefully, or you may get the spring too weak before you suspect it. Another and perhaps later process is as follows: - Fit the collet, without removing the spring, upon a stick of pivot wood, and having prepared a little diluted nitric acid in a watch-glass, plunge the centre coils into it, keeping the other parts of the spring from contact by holding it in the shape of an inverted hoop skirt with your tweezers.
To clean a Hairspring, immerse it in benzine and leave it there for a few minutes; if you watch it, you will see all the little particles of dirt and oily matter leaving the spring; after they are all off, lay the spring flat on the paper and just hold the chamois leather in your finger and press carefully on the spring: this will soon dry it.
First dissolve 1/2 oz. potassium cyanide in hot water: to this add 2 oz. strongest ammonia and 1/2 oz. spirits of wine. Dip the dial for a few seconds, and immediately immerse in warm water, brushing it lightly with soap; this will soon show a clean dial; then rinse, and dry off in hot boxwood dust. Some use diluted nitric acid for cleaning dials, or soda hyposulphite will do it, if dissolved and mixed with am-monia; but with either of these the painted numbers go with the dirt, so. only dials with gold numbers can be done with this process.
Amongst the various repairings it will often happen that new dials are required to replace damaged ones, and it is well known how seldom the feet of these new dials correspond with the old holes in the plate. The making of new holes sometimes meets with some obstacles, as they (the holes) occasionally would come in contact with parts of the movement. In such cases, it is best to cut the feet off, and carefully file flat with the enamel, then hold the dial in the proper place on the plate, and mark through the old holes the place for the feet to fill these holes; remove the enamel on these marked places with an emery file until a small space of the copper is laid bare. Then cut 2 feet out of an old dial, so as to leave a small plate on them, and solder these to the places for the purpose on the new dial. With a little care and practice the experiment will not fail to give the desired result, as regards strength of the feet and the neat fitting into the proper holes.
To effect the best possible results in timing an ordinary watch to the various positions, it is absolutely necessary to strictly observe the condition of the pivots of the cylinder or staff in lever, etc, escapements, and the jewel holes in which the pivots run. The pivots ought in all cases not to be unnecessarily long, be made conical at the shoulder and elongating, perfectly cylindrical for about 1 1/2 the length of the jewel hole, in order to rest freely on the cap jewel. When the watch is in a horizontal position, the point of the pivot should be quite flat, with merely the sharp edge removed and well polished; a pivot so constructed will work easy in all positions, and be least exposed to bending or breaking. The hole in the jewel should always be of the same length as the width of it, which is the proper size to equalise the friction of the pivot, whether the watch be in vertical, horizontal, or slanting position. If the hole is found to be larger than the diameter, the length can easily be reduced with the aid of a diamond drill, the end of which to be of a round instead of a sharp-pointed shape; or too large a hole may be reduced in a few seconds.
The bars of the polished steel effected in the hollow of the jewel is quite immaterial to the action of the pivot, as long as it is kept clean. Last of all, the balance should be carefully poised, and the balance spring be kept quite flat and free.