TECHNICAL GUIDE
Cal. 4R35A
18/18
Measure the rate in three different positions within 30 minutes after the watch is fully wound up (wait
approximately for 5 minutes after winding up in order to get a stable oscillation of the balance) and
make sure the value shows within the range in the table below.
Measure the rate in dial-up position after 24 hours from fully wound up (T24) and check the rate
difference with the rate in dial-up position when it is fully wound up (T0). Make sure that the value of
T24-T0 shows within the range of the isochronism in the table below.
v T
he accuracy of mechanical watches is indicated by the daily rates of one week or so.
v T
he accuracy of mechanical watches may not fall within the specified range of time accuracy because
of loss/gain changes due to the conditions of use, such as the length of time during which the watch
is worn on the wrist, arm movement, whether the mainspring is wound up fully or not, etc.
v The key components in mechanical watches are made of metals which expand or contract depending on
temperatures due to metal properties. This exerts an effect on the accuracy of the watches. Mechanical
watches tend to lose time at high temperatures while they tend to gain time at low temperatures.
v I
n order to improve accuracy, it is important to regularly supply energy to the balance that controls
the speed of the gears. The driving force of the mainspring that powers mechanical watches varies
b
etween when it is fully wound and immediately before it is unwound. As the mainspring unwinds,
the force weakens.
v Relatively steady accuracy can be obtained by wearing the watch on the wrist frequently for the self-
winding type and winding up the mainspring fully everyday at a fixed time to move it regularly for the
wind-up mechanical type.
v
When affected by external strong magnetism, a mechanical watch may loss/gain time temporarily.
The parts of the watch may become magnetized depending on the extent of the effect. In such a case,
consult the retailer from whom the watch was purchased since the watch requires repair, including
demagnetizing.
Standard rate
for
measurement
Mainspring
wind up status
Fully wind up (T0)
Af
ter 24 hours
from fully wind
up (T24)
Testing
positions
Di
al upwards:
T0 (CH)
6 o'clock at the
top
9 o'clock at the
top
Di
al upwards:
T24 (CH)
Measurement
(daily rate in
seconds:s/d)
±20 s/d ±30 s/d ±30 s/d
( Iso chronism
fault: T24-T0)
±30 s/d
l
Duration time test
Check the Power reserve of the watch after the mainspring is fully wound up and leave it oon natural
condition with the dial-up position. Make sure that the watch runs approximately 41 hours until it
stops.
l
Accuracy test
ACCURACY OF MECHANICAL WATCHES
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