1. Excessive side friction of pivots because of being too large in diameter.

2. Train wheels and pinions being of incorrect proportion and causing irregular motion and affecting the vertical positions mostly.

3. Centrifugal force, which would cause the balance rims to spring outward in the longer arcs of vibration and thereby produce an abnormal slow rate in the horizontal positions where the arc of motion is always longest. This is due to the balance rims being too heavy in proportion to the arms or center bar.

When either of these three conditions are found there will be others among the same lot of watches, but as a rule they are only found on older watches made before correct proportions were firmly established.

Train depthings can often be improved if the workman is equipped with a rounding up machine and knows how to use it. Otherwise the watch can be sent to the factory for correction and the only alternative of the repairer is to cut the spring to the slow point, or counterpoise, with the intention of eliminating expense and getting as good results as can be expected for the financial returns that are to be received.

74. _How to Locate Defective Gearings._

Defective gear or depthing of wheels can be detected in two ways, one by observing the engaging surfaces of the wheel teeth and another by testing the engagement of wheel and pinion.

If the gearing is correct, observation will show that the engaging surfaces of the wheel teeth are smooth and either dark or possibly polished from wearing away of the plating. If the gearings are not correct the engaging surfaces will have cuts or ridges crosswise which have been produced by the pinion leaves.

The cause of this cutting is due to either a faulty construction of the teeth or to the fact that the pitch circle of the wheel is too small while that of the pinion is too large.

Testing the gearing in the watch is accomplished by placing the engaging wheel and pinion in the watch so that they are free to turn without engaging with any other wheel. A piece of ivory or celluloid several inches long and about the diameter of a piece of peg wood should be pointed at one end and this end should be held between the upper pivot and oil cup of the jewel, with enough pressure of the left hand to cause friction in turning the pinion. The larger wheel should then be turned in the direction in which it revolves when running; this is accomplished with a piece of peg wood held in the right hand.

If the gearing is perfect there will be smoothness as the wheel and pinion turn and if it is imperfect there will be a b.u.t.ting effect in the action. Should there be a slight intermittent stepping action due to drop of the wheel teeth on the pinion leaves it should not be mistaken for b.u.t.ting as this is not detrimental and will not cause cutting of the teeth.

Watches that have below standard train gearings require considerably stronger mainsprings than do those which have correct gearing and they will seldom take a reasonably good motion without a strong spring.

A safe way to judge gearings if in doubt is by the motion and the engaging surfaces of the wheel teeth. If the motion is steady and the teeth are not cut by the pinion leaves they may be considered as satisfactory. If the motion is steady for a time and then suddenly drops off there is generally something wrong in the gearing. The wheel and pinion in error can be determined by noting at what particular intervals the motion decreases. In nearly all instances this condition will cause a gaining rate in the vertical positions because of the fact that the vertical arcs are shorter and comparatively more easily affected than the horizontal arcs.

CHAPTER XV

TIMING AND FINAL REGULATION

75. _Mean Time Screws and Timing Washers._

In the general overhauling of watches, changing staffs, retruing and repoising of balances it is often necessary to make corrections of several minutes per day in the mean time.

For this reason and for the convenience of the future some manufacturers have provided from two to four mean time screws in the balances. A complete revolution of these screws either in or out, generally corrects any variation that may be required and frequently considerably less is all that is required in bringing the watch to time.

It is of course necessary that these screws be turned in opposite pairs as well as equal distances and that they be fitted with enough friction to prevent looseness and not too tight to cause bending of the pivots when they are turned.

If properly used for the purpose for which they were intended they are of inestimable value to the repairing fraternity in producing results.

The manufacturers of some watches do not supply mean time screws with the balances and the repairer is obliged to depend entirely upon timing washers for fast corrections, for it is, of course, not to be expected that repair shops will carry an a.s.sortment of all different kinds of screws such as the factories are able to maintain.

Occasionally a jeweler or watchmaker will be found who has strenuous objections to the use of timing washers in any sense, but unless they are supplied with a large a.s.sortment of the various makes and weights of screws and are willing to use the extra time required for properly changing the screws it is difficult to see just what legitimate alternative they can adopt. Investigation of this point disclosed the fact that the method employed by some watchmakers was to spread the regulator pins, which would of course make the mean time slower but would certainly destroy the adjustment to positions and make it practically impossible to obtain results from the regulator.

It is admittedly poor workmanship to use ill-fitting washers and poor taste to use bra.s.s washers on high grade gold screw balances, but the fact should not be overlooked that the manufacturers of many fine watches use washers to a limited extent, even when an abundance of balance screws are available and very fine Swiss models are often supplied with a pair of thin platinum washers which are not easily detected. The regulator should not be moved from the center of the index in correcting the mean time but should be used for minor final regulation only. The length of the hairspring should also not be disturbed in correcting the mean time of an adjusted watch and while a slow rate can be corrected by reducing the weight of a pair of balance screws it is necessary to use either heavier screws or washers for correcting a fast rate.

76. _Importance of Properly Fitted Regulator._

Final regulation of watches is necessary after making repairs regardless as to whether they have been adjusted to positions or not.

Position rating does not necessarily suggest that the timing has been completed as the object is only to limit the variations from one position to any other and a test of three or four days should always be made in one position after the position rating has been completed.

This additional timing has for its purpose the close regulation of the watch either in the pendant up position or in the position it is carried. The last column on the rate card is reserved for this purpose. In this respect the repairer who comes in contact with the customer may gain considerable advantage by noting in which pocket the watch is usually carried and then being guided in the final regulation by this knowledge. The method of doing this regulating consists generally of moving the regulator which requires certain attention to be effective when it is moved.

The regulator should be carefully fitted around the dome and all attachments in connection should be tightly fitted to the plate or bridge so that they will remain rigid when regulation takes place.

The tension around the dome should be even and if a tension spring is used in connection it should be strong enough to keep the regulator against the screw constantly without sticking at any point as the screw is moved forward and backward.

It should also be closely examined to see that there is no shake. This can be determined by lightly taking hold of the segment holding the regulator pins and moving it up and down and side ways before the tension spring is fitted. This should be examined with a gla.s.s and a correction made if any looseness is noted.

77. _Effect of the Middle Temperature Error._

In the final regulation of watches it is important that the middle temperature error receive due consideration. This error is always a few seconds fast as explained in temperature adjusting Chapter V, No.

21, and is of some consequence in the larger number of complaints regarding losing rates in the pocket, compared to complaints of gaining rates.

The position rating as well as the final regulation is generally done in normal temperature which produces a rate from two to four seconds faster than the heat extreme and it is to be expected that the pocket rate will be slower because the temperature will be higher than normal. This loss may not be the full amount of the middle error as it would depend upon the actual temperature encountered for the entire twenty-four hours and the watch may only be subjected to the pocket temperature for a part of this period. This works in exactly the same way in a lower temperature, as the variation is a loss in either direction from the middle or normal temperature and in case that the watch should be subjected to a freezing temperature at night the result will be a loss during that period.

As an example we will a.s.sume the regulation of a watch in which the temperature rate at the extremes of 40 and 90 Fahr. is perfect, while at the temperature of 70 it will time four seconds fast.

Now if this watch is regulated to no variation in the normal temperature it will be plainly seen that there will be a loss of four seconds per day if the watch is placed in service at either of the temperature extremes. If it had been regulated to run four seconds fast in the middle or normal temperature it would time more nearly correct in the pocket.

It is safe to a.s.sume that the watch will lose its proportional rate with a lesser change in temperature and for this reason it is of advantage to finally regulate all watches from two to four seconds fast in the rack rather than to time them just correct.

78. _Some Practical Reasons for Slow Rates._

There are additional reasons for the suggestion of timing watches a few seconds fast rather than just correct. Among them may be mentioned the fact that many watches are carried in the left vest pocket, and that in this instance they very often a.s.sume the pendant right position which is generally a trifle slow compared to pendant up in most watches of close adjustment. Magnetism to any extent whatever always causes a slow rate and this will have its effect whenever the balance, hairspring, regulator, regulator spring or pallet are slightly effected or when the mainspring, large winding wheels or case springs are considerably charged and experiments have shown that in no instance has a fast rate been produced from this cause.

The gradual weakening or loss of elastic force of the hairspring is also a factor to be considered.

There are some influences which cause a gaining rate that to some extent may offset these losses, although in the absence of necessity for cleaning or other repairs these influences are slight in comparison to the natural and possible causes for a slow rate.

PART III

SPECIAL NOTES