Practical Watch Repairing by Donald De Carle

Author:Donald De Carle
Language: eng
Format: epub, pdf
Publisher: Crowood

Fig. 243. The arc of vibration of the balance.

It can be taken as a standard that if the watch is to function satisfactorily, the arc of vibration of the balance should not be less than turns or more than turns, dial up or down, and not less than turns PU or in the vertical position. If the arm under observation reaches to the other side, that is half a turn, then the balance is said to be crossing or vibrating one turn. One turn, because it must take half a turn backwards as well as forwards. Therefore if the arm reaches another turn further on, that is of a turn in one direction, it is equal to turns, or it crosses turns. The illustration (Fig. 243) will help you to ascertain the arc of vibration of the balance. A little practice is necessary before being able to determine the extent of the arc quickly. First, note the position of the arm with relation to some part of the watch, say the balance spring stud. Then hold the pegwood pointer at the point of commencement—that is the arm—and move the pointer round as the balance increases its arc, so that at each swing the balance arm reaches the pointer. When the balance arm has reached its maximum, the position of the pointer with relation to the balance spring stud will give us the arc of the balance. With a little practice you will be able to dispense with the pointer.

Although a timing tool was used when fitting the balance spring, the watch will need regulating to bring the watch to time dial up over a period of 24 hours. It must be borne in mind that the timing tool gives the count of the balance when perfectly free, not even the friction of the balance pivots are taken into consideration. In addition to this, the interference of the escapement, the action of the ruby pin, unlocking, etc., all have their effect upon the rate of the vibrations of the balance. Another point to consider is that the timing tool gave us the “perfect” time at one particular time; when the balance is in the watch the power of the mainspring will vary, and with it the arc of vibration of the balance, and the extent of the arc of the balance influences the timekeeping. So, as you see, the timing over a period of 24 hours is another story to the timing on the vibrating tool—and this equally applies to timing machines.

Should it be found necessary to make an alteration for a considerable error, the adjustment must be done by altering the weight of the balance. On no account may the balance spring be et o ut or taken in, as this will alter the theoretical terminal—this does lnot apply to a flat balance spring—nor should the index be moved to any extent, for the same reason. In order to simplify matters, bring the watch to within a few seconds in 24 hours, we shall then not be confused with lengthy calculations.

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