Cautions for accuracy of mechanical watch
Mechanical watches have a mechanism that is moved by power generated when the
mainspring is unwound, and small metal parts physically work together to control the
accuracy. Fragile metal parts of a mechanical watch are easily influenced by external
environment such as temperature, gravity, and shock. Also, conditions of use such as normal
usage time and winding state of the mainspring can influence the loss/gain of the watch.
1
Accuracy of mechanical watch is “mean daily rate.”
Accuracy of the quartz watch is indicated monthly or annually such as a monthly rate of
±15 seconds or annual rate of ±10 seconds. This indicates the degree of total difference
in accuracy when the quartz watch is continuously used for a month or a year.
To the contrary, accuracy of the mechanical watch is normally indicated as a “mean daily
rate.”
Accuracy of the mechanical watch slightly varies each day as it is influenced by various
conditions of use, and it is normally unstable. Then it is required to judge whether the
accuracy is satisfactory or not by checking the mean values in the case of use for a week
to ten days, but not for only one day.
For normal usage accuracy of Grand Seiko mechanical watch, -1 to +10 seconds (–1 to
+8 seconds for Cal. 9S86 and 9S85, –5 to +10 seconds for Cal. 9S27) per day are specified
as target values. If the mean value exceeds the abovementioned target value in the normal
usage condition when the watch is used for a week to ten days, we recommend adjusting
it.
* Please note that the parts that are age-deteriorated due to long duration of use may not be
adjusted to your desired accuracy. For details, refer to P. 39.
2
Factor influencing accuracy (1): Wound amount of the mainspring
In order to use the mechanical watch at better accuracies, it is required to supply a constant
strong energy wherever possible to respective parts.
In the state where the mainspring is fully wound, accuracy is stable, however, when the
mainspring is unwound to weaken energy to be supplied, the parts controlling accuracy
tends to be externally influenced, and accuracy becomes unstable.
In order to use a mechanical watch at a steady accuracy, it is recommended to use it in a
condition where the mainspring is sufficiently wound.
3
Factor influencing accuracy (2): Temperature influence
Mechanical watch parts are metal which slightly elongate and contract by change in
temperature, and this influences accuracy. Normally, under high temperatures, it tends to
lose time, and under low temperatures, it tends to gain time.
4
Factor influencing accuracy (3): Difference by position (orientation of a watch)
Parts related to accuracy of a mechanical watch are also influenced by the earth’s gravity.
For example, gain or loss differs when a watch is horizontally placed and when it is vertically
placed in the 12 o’clock up position.
When the watch is not worn on the wrist, accuracy errors that occur while wearing can also
be compensated to some extent according to the position. Try to place it in various positions
to find the position appropriate to your watch.
38
THE GRAND SEIKO STANDARD
■
TO PRESERVE THE QUALITY OF YOUR
WATCH
After-sale service
Notes on guarantee and repair
○ Contact the retailer from whom the watch was purchased or Grand Seiko international
service network mentioned on CERTIFICATE OF GUARANTEE or our website for repair
or overhaul.
○ Within the guarantee period, present the certificate of guarantee to receive repair services.
○ Guarantee coverage is provided in the certificate of guarantee. Read carefully and retain
it.
○ For repair services after the guarantee period has expired, if the functions of the watch can
be restored by repair work, we will undertake repair services upon request and payment.
Replacement parts
○ Please keep in mind that if original parts are not available, they may be replaced with
substitutes whose outward appearance may differ from the originals.
Inspection and adjustment by disassembly and
cleaning (overhaul)
○ Periodic inspection and adjustment by disassembly and cleaning (overhaul) is
recommended approximately once every 3 to 4 years in order to maintain optimal
performance of the watch for a long time.
○ The movement of this watch has a structure that consistent pressure is applied on its power-
transmitting wheels. To ensure these parts work together properly, periodic inspection
including cleaning of parts and movement, oiling, adjustment of accuracy, functional check
and replacement of worn parts is needed. Inspection and adjustment by disassembly and
cleaning (overhaul) within 3 to 4 years from the date of purchase is highly recommended
for longtime use of your watch. According to use conditions, the oil retaining condition of
your watch mechanical parts may deteriorate, abrasion of the parts may occur due to
contamination of oil, which may ultimately lead the watch to stop.
As the parts such as the gasket may deteriorate, water-resistant performance may be
impaired due to intrusion of perspiration and moisture.
Please contact the retailer from whom the watch was purchased for inspection and
adjustment by disassembly and cleaning (overhaul). For replacement of parts, please
specify “GRAND SEIKO GENUINE PARTS”. When asking for inspection and adjustment
by disassembly and cleaning (overhaul), make sure that the gasket and push pin are also
replaced with new ones.
○ When your watch is inspected and adjusted by disassembly and cleaning (overhauled),
the movement of your watch may be replaced.
39
TO PRESERVE THE QUALITY OF YOUR WATCH
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