Seiko 6R21 Instructions - Page 22

Accuracy of Mechanical Watches

○ The accuracy of mechanical watches is indicated by the "daily rate."

○ The accuracy of mechanical watches may not fall within the specified range of

time accuracy because loss/gain changes due to the position of the watch,

which is dependent on the conditions of use, such as the length of time during

which the watch is worn on the wrist, arm movement, and whether the

mainspring is wound up fully or not, etc.

○ The loss/gain of mechanical watches is not measured by a daily rate, but by

daily rates of one week or so.

○ Accuracy variation according to temperature

The parts that compose the accuracy of mechanical watches are made of

metals. It is well known that metals 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.

82

○ Mainspring wound condition and accuracy

In 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 between when fully wound

and immediately before it is unwound. As the mainspring unwinds, the force

weakens.

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.

○ Effect of magnetism

When affected by a strong magnetism from outside, the mechanical watch

may lose/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.

83

Specifications

＊The accuracy above is factory-adjusted.

＊Due to the characteristics of mechanical watches, any actual daily rate may not fall within the range of time

accuracy specified above dependent on the conditions of use, such as the length of time during which the watch

is worn on the wrist, temperature, arm movement, and whether the mainspring is wound up fully or not, etc.

Cal.

１.Function

6R20／6R21

Time display (Hour, minute and second hands),

day and date display,power reserve

indicator

6 hands

2.Vibrations per hour

28,800/Hour

5.Driving system

Automatic winding type with manual winding mechanism

More than approx. 45 hour

6.Jewels

29 jewels

3.Loss/gain

(daily rate)

+25 ～ -15seconds at normal temperature range

(between 5℃ and 35℃)

4

.Continuous operating time

84

本　社　〒105-8467

東京都港区芝浦1-2-1

http://www.seiko-watch.co.jp/

東京都千代田区丸の内

3-1-1

国際ビル

大阪市西区新町 1-4-24

大阪四ﾂ橋新町ビルディング

100-0005

550-0013

〒

〒

お客様相談室

全国共通フリーダイヤル

0120-612-911

Seiko 6R21 Instructions - Page 22

Specifications

Page 22 highlights