a.s.suming, however, that the motion is good in one position and drops off in the other, it is quite probable that only an ordinary position correction will be required and the immediate problem to be considered is that of causing the short arc of motion to accelerate enough to equal the longer arc. The precise correction required will most probably be found among the causes listed in No. 46, this Chapter.
52. _Which Rate to Use as the Unit for Comparison._
The horizontal position which has the slower rate of the two should be considered as the unit which is correct and it will always have the longer motion of the two, barring the occasional exception as described in No. 50.
This longer arc of motion is universally due to a better condition, while the shorter motion indicates that something is wrong, and it should always be the aim of the adjuster to improve some condition that is below standard, rather than to make some good condition a little worse in order to equalize the rates.
It may be possible to equalize horizontal rates by flattening the ends of pivots, but it does not require much more time to improve the motion in one position than it does to make it a little worse in another. The advantage is all one way and results either good or bad depend entirely upon the viewpoint of the worker and how he applies himself to the situation.
53. _Damaged Pivots, Pitted End Stones and Methods of Correction._
In the examination of pivots, end stones and jewels, it is necessary to use a stronger gla.s.s than the one used for ordinary work.
Damaged pivots can often be detected by looking through the end stone with a strong gla.s.s while the balance is moving. If imperfect they will appear dark or display a slight waver or flash and if they are in good condition they will appear bright and seem to stand still. They can also be examined in the lathe and a good true enclosed balance chuck is of immense value in detecting burrs, chipped edges, rings on the sides, slight bends and poorly shaped ends. The complete balance and spring can be inserted and the pivots can be refinished without disturbing the roller or hairspring. The chuck should be revolving very slowly when making the examination and moving the belt with the hand will enable one to see more than can be seen when the lathe is running at regular speed. Some watchmakers use small bow lathes for examining and finishing pivots, or the Jacot lathe, which is excellent for this kind of work. An end stone that has been deeply pitted should always be discarded and a new one supplied. If the hole is very slight, however, it can be removed entirely and the surface of the stone re-polished on a lap charged with No. 5 diamond powder, but the stone and setting should be thoroughly cleansed by brushing and pithing before replacement.
Should a slight particle of diamond or any other hard stone powder possibly remain on the stone or in the bezel it might eventually enter the end of pivot and again cause pitting. In case that the end stone is of the type that is flat and highly polished on both sides, such as is usually found on detachable dome foreign watches, it can be punched out with a piece of bra.s.s wire or peg wood and replaced in reverse position, after which the bezel can be closed and the stone will be just as serviceable as a new one.
Pivots that have been running on pitted end stones are generally rough on the end which is charged with some hard substance. They require special treatment to remove the cause of the pitting and the following method of refinishing is very good. Place the balance in the lathe and draw a soft Arkansas oil stone over the end of pivot with pressure enough to remove a bit of the metal. This will drag out any hard particles that may be lodged in the end and after this has been done the pivot should be pithed clean and polished with a smooth hard steel burnisher covered with oil.
A hard stone such as sapphire or jasper, or a steel burnisher should not be used on the pivot until the Arkansas stone has first done its work, because a hard instrument of this description will force the small particles that cause the pitting further into the end of the pivot instead of removing them entirely.
A pivot that has been treated in this way will not pit the end stone a second time unless carelessness in the use of hard powder permits additional particles to come in contact with the pivot or end stone.
There are some instances in which the steel is highly carbonized but manufacturers generally use the best steel obtainable for balance staffs and excessive carbon can generally be detected with a magnifying gla.s.s. Free use of diamond powder and emery wheel dust are more often responsible. The holes of jewels should never be enlarged or polished with diamond powder after the jewels have once been placed in their permanent settings, as this allows the powder to lodge between the jewel and the setting where it cannot be removed by cleaning but where it will be drawn out by the oil and charge any pivot that may be run in the jewel. The grey powder in such instances may be seen through the top of jewel with a strong gla.s.s.
FOOTNOTES:
[Footnote B: Note Exceptions in No. 50.]
CHAPTER XII
PRELIMINARY NOTES AND PRACTICE ON VERTICAL CORRECTIONS
54. _Five Princ.i.p.al Causes and Corrections for Pendant Up Variation._
The first of the vertical positions to be considered is that of Pendant Up and to understand the causes of and corrections for variations in this position completes what is known as three position adjusting.
The usual causes of variation in the pendant up position as compared to the horizontal positions are as follows.
Poor Motion Pendant Up.
Regulator Pins not properly adjusted.
Balance not in poise.
Hairspring not in circle.
Hairspring not pinned at proper point.
55. _Poor Motion, Cause and Effect._
Among these causes that of Poor Motion covers a number of troubles such as roller jewel rubbing in fork, guard pin rubbing roller, strong lock on the escapement, or no lock on some teeth.
Such causes may not prevent close rating between the horizontal positions because of non-interference until the position of the watch is changed.
The pendant up motion should therefore be the first vertical point of investigation and if at fault the cause should be eliminated. In this connection it should not be expected that the arc of motion in the pendant up or any other vertical position will be as long as it will be in the horizontal positions, for when a watch is in excellent condition in every particular the vertical arcs are always approximately one-fourth of a turn shorter than the horizontal.
This is due to frictions and is impossible of correction and therefore should not be confused with a poor motion of greater extent which has removable causes that are practical of execution.
A good motion is to be considered as one of the results to be expected in overhauling and putting a watch in good order and it should not be understood that it is particularly to be a.s.sociated with adjusting only, nor should any watch be slighted in cleaning and a.s.sembling with the idea that adjusting will correct it in a few minutes" time. On the other hand it should be understood as fundamental that no watch can be a close time keeper unless it has a good motion and no good adjuster will attempt to obtain close time in one position or a close rate in different positions until the motion is first what it should be. If it is what it should be, about ninety per cent of the necessary work required for obtaining close position rates will have been completed.
56. _Regulator Pin Practice for Pendant Up Variation._
When the watch is in reasonably satisfactory condition and a three position test proves that the pendant up position has a variation of from ten to twenty seconds either fast or slow compared to the horizontal positions, the regulator pins may be the first point of examination. If there is considerable vibration of the coil between them, and the pendant rate is slow, it will be necessary to close the pins and if the rate is fast and the pins are found to be closed so that there is no vibration of the coil, it will be necessary to spread them slightly. Closing the pins will of course make the general timing of the watch faster and spreading them will make it slower and therefore it will be necessary to regulate the watch for one or two seconds per hour before again testing it in positions. The result of either operation, however, will be to cause the rate in the pendant up position to conform more closely to the horizontal rates.
Preliminary and profitable two position experiments can be made between dial up and pendant up, by having the pins closed on most any watch that is in good order and timing it within five or ten seconds in twenty-four hours, then rating it in these two positions. Next spread the pins slightly, re-time the watch and rate it in the same two positions and compare the variations. A few experiments of this description will soon demonstrate as to the extent of correction that can be obtained in this way.[C] The rule of equal vibration of the coil between the pins after they have been spread must be rigidly enforced.
57. _Pendant Up Corrections Through Poise of Balance._
a.s.suming that the motion and regulator pins seem to be satisfactory, the next point of investigation should be the poise of balance. The hairspring should be removed and the pivots known to be straight and polished before testing. The rollers are of course a part of the balance and are not to be removed. A perfectly poised balance can be stopped at any point on the tool and it should at least remain stationary at each of the four quarters of its circ.u.mference. No. 28, Chapter VII, should be consulted for details on poise corrections.
58. _Concentricity of the Hairspring._
The next point of consideration may be the concentricity of the hairspring, and it is quite important that the spring be centered as nearly perfect as the trained eye can determine. Any unusual pressure of the spring in one direction will cause undue friction and a fast rate compared to the opposite direction.
There are several easy tests for determining as to how nearly the spring may be centered. One of these is to look straight down upon the spring and examine the s.p.a.ce between the coils that extend beyond the circ.u.mference of the dome. This test may be made in three ways, one with the balance at rest, one with the coils of the spring wound up and the third with the coils unwound. With the balance at rest and the spring centered there will be the same s.p.a.ce between the coils all around as though the spring were out of the watch entirely and laying on the bench.
If it is not properly centered there will be more s.p.a.ce between the coils on one side than there will be on the opposite. The same conditions will be apparent when the spring is wound up, although the coils will all be nearer to each other than they were with the balance at rest, and when they are unwound the coils will all be farther apart with the same apparent difference on opposite sides when the centering is not correct.
The winding and unwinding of the spring is alternating and almost instantaneous, as the balance oscillates from one extreme to the other. For observation of the spring when it is wound or unwound it is necessary to stop the balance with the finger or camel"s hair brush as it reaches its extreme arc of motion, then hold it stationary for a few seconds while the s.p.a.ce between the coils is being examined. The balance should then be allowed to swing to the opposite extreme, when it should again be held for examination of the coils. In one of these extremes the coils will be wound and in the other they will be unwound and after a few experiments in stopping and starting the balance it will be found that the entire examination will not require over ten seconds" time.
When the spring is not properly centered the reason is of course found in some curve of the over coil and the most usual point at fault is the section or curve on which the regulator pins act. If the coils open too wide on the side where the regulator pins are located this section of the coil will be too near the center and should be moved outward, possibly equal to one-half or one full s.p.a.ce of the coils. If the coils are too close on the side where the pins are it will probably be found that the section requires shifting toward the center slightly. The balance should be removed from the watch in either instance and the coil circled with the over-coiling tweezer, although experienced workmen can frequently make excellent corrections with a fine pointed tweezer without removing the balance.
Finely adjusted watches will always be found to have springs as nearly perfectly centered as it is possible for expert workmen to get them and it is quite interesting and instructive to observe the vibration of a perfect spring by any one interested in the work.
Some watchmakers center the spring on the balance c.o.c.k before it is staked on the balance and very good results can be obtained in this way. The balance c.o.c.k is placed on the bench in the inverted position which makes it easy to locate the point or curve requiring alteration.
59. _Correcting Pendant Up Variation Through Pinning Point Alterations._
Should most careful investigation of the condition of the watch indicate that the Motion, Regulator Pins, Poise of Balance and Centering of the Hairspring as well as the general condition of the watch are satisfactory and the rating show that there is still considerable variation between the horizontal positions and the pendant up position there is still one source through which positive correction may be obtained.
This refers to the relative positions of the collet and stud pinning points which is defined with explanatory cuts and formula in Chapter VIII.