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 associated with adjusting only, nor should any watch be slighted in cleaning and assembling 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.
Assuming 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 circumference. No. 28, Chapter VII, should be consulted for details on poise corrections.