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Authored by Tokunaga

Question: From John L-san

I was wondering about the Seiko entry level mechanical movt. 7S26 & 7S36 found in many divers and Seiko 5's. My experience with those movt. as well as many others here on the forum, is that they tend to run fast from the factory. Sometimes as much as +60 sec./day. These movt. are very well made and are capable of up to +2 sec./day when regulated from my understanding.

My question is why doesn't Seiko regulate them from the factory, better then 30,45,60 sec. faster than real time? These movt. are capable of tighter regulation and it would seem to me that that could be regulated at the factory. This would result in the watches being sold to be very accurate right out of the box.

Is this not done do to the higher cost at the factory? Maybe the cost would be too high.

I have read accounts of the higher end movt. in the King Seikos, Grand, Cretor, to come out of the box very accurate.


As for the accuracy of the mechanical watches, daily rate is about + or - 20 sec./day on the medium-class watches, it will be about + or - 40 sec./day in case of the popular-class watches, and about + or - 5 sec./day in case of the high precision watches such as chronometer.

Since the delay of time poses a problem on social life, daily rate is adjusted to a little fast than the center, in order to that the accuracy of the watches go by the side of safety.

In case of the standard of chronometer, the permissible accuracy range is adjusted to the plus side, as +6 to -4 sec./day, and Cal.9S(4Hz) of the present Seiko caliber is in this class. Since Cal.7S(3Hz) is a popular-class mechanical watch, it consists of +45 to -35 sec./day, and Cal.4S(4Hz) is from +25 to -15 sec./day as medium-class mechanical watch.

On the present mechanical watches, since 8 beats/sec. (4Hz) is the highest, there is no + or - 2 sec./day level Caliber which had realized by VFA(Very Fine Adjusted) of old grand Seiko (10 beats/sec.) at present.

Concerning the cost, except for the case where it is not adjusted at all, the cost of the almost same amount occurs regardless of the amount of adjustments.

Sincerely yours,

Ikuo Tokunaga

Ikuo Tokunaga

Picture credit: Seiko
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