Seiko Calibers 6R20/6R21/6R24/6R27

Table of Contents

• Mechanical Watch Characteristics

• Part Names

• Usage

• How to Set Time, Day of the Week, and Date

• How to Read the Power Reserve Indicator

• Care for Your Watch

• Where to Store Your Watch

• Periodic Checks

• Warranty and Repair

• Troubleshooting

• Accuracy of Mechanical Watches

• Specifications

Part Names

The diagrams below illustrate the parts of the watches for Calibers 6R20/6R21 and 6R24. The appearance of the dial may vary depending on the model.

Caliber 6R20/6R21

Diagram Description: A watch face is shown with various hands and indicators. The main dial displays the hour, minute, and second hands. Additional sub-dials or indicators are present for the day of the week and the power reserve. The winding crown is located on the side of the watch case.

Key Components Labeled:

• Hour Hand
• Minute Hand
• Second Hand
• Day of the Week Indicator
• Date Indicator
• Power Reserve Indicator
• Winding Crown

Caliber 6R24

Diagram Description: Similar to the 6R20/6R21, this diagram shows a watch face with hour, minute, and second hands. It features a day of the week indicator and a date indicator. The power reserve indicator is also present. The winding crown is on the side.

Key Components Labeled:

• Hour Hand
• Minute Hand
• Second Hand
• Day of the Week Indicator
• Date Indicator
• Power Reserve Indicator
• Winding Crown

Winding Crown Positions

The winding crown has three positions:

• a) Normal Position: For manual winding of the watch.
• b) Pulled out to the first click: For setting the date and day of the week.
• c) Pulled out to the second click: For setting the time.

Usage

How to Wind Your Watch

These watches are equipped with both automatic and manual winding functions. When worn on the wrist, the watch is automatically wound by the movement of your arm. If the watch stops, it is recommended to wind it manually using the crown.

Manual Winding Procedure:

1. Slowly turn the winding crown clockwise (towards the 12 o'clock position). Turning the crown counter-clockwise (towards the 6 o'clock position) does not wind the mainspring.
2. Continue turning the crown until the power reserve indicator shows the maximum reserve. The second hand will begin to move.
3. Set the time, day of the week, and date before wearing the watch.

Important Notes:

• To check the mainspring's winding status, refer to the "How to Read the Power Reserve Indicator" section on page 146.
• There is no need to force the crown when the mainspring is fully wound; it can be turned without damaging the watch mechanism.
• A fully wound watch will operate continuously for approximately 45 hours.
• Using the watch when the mainspring is not fully wound may cause variations in timekeeping. To ensure optimal performance, wear the watch for at least 10 hours a day. If you do not wear the watch, wind it manually every day at the same time.
• If the watch has stopped and the mainspring is not wound, winding it may not start the watch immediately. This is because the initial torque from the mainspring is low. Gently shake the watch from side to side to help start the movement.

How to Set Time, Day of the Week, and Date

Before setting the day of the week, date, and time, ensure the watch is running. The 6R27 caliber shows only the date.

The watch is designed so that the day of the week and date change approximately every 24 hours. The date typically changes at midnight, and the day of the week changes around 2 AM. If the AM/PM indicator is set incorrectly, the date may change at noon and the day of the week at 2 PM.

Setting the Day of the Week and Date:

1. Pull the winding crown out to the first click. The second hand will continue to move, ensuring the watch's accuracy is not affected.
2. Set the day of the week by turning the winding crown clockwise.

For Caliber 6R24:

• Avoid setting the day indicator between two days.
• If you turn the crown to set the day when it indicates Saturday, it may jump back to Sunday. If it skips Sunday and stops on Monday, reset it slowly.

3. Set the date by turning the winding crown counter-clockwise. Turn it until the previous day's date is displayed. For example, if today is the 6th, set the date to "5" by turning the crown counter-clockwise.

For Caliber 6R24:

• If you turn the crown when the date indicator is at 31, it may revert to 1.

Warning: Do not set the date between 21:30 and 2:00. Doing so may cause the date to change incorrectly, leading to a malfunction.

Setting the Time:

1. Pull the winding crown out to the second click when the second hand is at the 12 o'clock position (the second hand will stop).
2. Turn the winding crown until the date changes to the next day. This indicates that the current time is in the AM period. Continue moving the hands to set the current time.
3. Return the winding crown to the normal position simultaneously with a time signal (e.g., a radio time signal).

Note on Mechanical Watch Accuracy: When setting the time, it is recommended to set the minute hand slightly before the desired time, then advance it to the exact time.

Correction of Date at the Beginning of the Month:

Manual date correction is required at the end of months with fewer than 31 days. For example, after a 30-day month, if the watch shows "31" instead of "1":

1. Pull the winding crown out to the first click.
2. Turn the winding crown to set the date to "1", then return the crown to the normal position.

Warning: Do not set the date between 21:30 and 2:00. Doing so may cause the date to change incorrectly, leading to a malfunction.

How to Read the Power Reserve Indicator

The power reserve indicator shows the winding status of the mainspring. Before removing the watch, check the position of the indicator to ensure it has enough power to continue running. If necessary, wind the mainspring to provide sufficient reserve for uninterrupted operation.

Notes:

• When the mainspring is fully wound, the winding crown can be turned freely without damaging the mainspring. The watch is equipped with a stopper mechanism to prevent over-winding.
• The position of the power reserve indicator may vary depending on the model.

Care for Your Watch

Under normal circumstances, your watch requires minimal special care and will function reliably for many years. To ensure its longevity and prevent skin irritation:

• Wipe off moisture, sweat, or dirt with a soft, dry cloth immediately after removing the watch.

Leather Strap Care:

• Gently blot moisture from the strap using a soft, dry cloth. Avoid rubbing the leather strap, as this may cause damage or color loss.

Metal Bracelet Care:

• To maintain cleanliness, use a soft toothbrush dipped in clean or soapy water. Be careful not to let water enter the watch case.

Warning: Skin Rash and Allergic Reaction:

• Adjust the strap so that there is a slight gap between it and your wrist to allow for ventilation.
• For some individuals, prolonged contact with the watch may cause skin irritation or an allergic reaction. Possible causes include:
• Allergic reactions to metals or leather materials.
• Accumulation of rust, dirt, or sweat on the watch or strap.
• If you experience any allergic symptoms or skin irritation, discontinue wearing the watch immediately and consult a doctor.

Precautions When Wearing Your Watch:

• Exercise caution when holding an infant or small child while wearing your watch, as they could be injured or develop an allergic reaction from direct contact with the watch.
• Avoid impacts, drops, or scratches against hard surfaces, as well as strenuous sports activities that could cause temporary malfunctions in your watch.
• There is a possibility of injury when wearing a watch, especially if you fall or collide with other people or objects.

Where to Store Your Watch

• Avoid storing the watch at temperatures below 5°C (41°F) or above 35°C (95°F).
• Do not leave the watch in locations exposed to strong magnetic fields (e.g., near televisions, speakers, or magnetic bracelets) or static electricity.
• Do not leave the watch in places with strong vibrations.
• Do not leave the watch in dusty environments.
• Do not expose the watch to chemicals or gases (e.g., organic solvents like benzine and thinner, gasoline, nail polish, cosmetic sprays, detergents, adhesives, mercury, and iodine-based antiseptics).
• Avoid direct contact with hot water.

Periodic Checks

This watch is a precision instrument with many moving parts lubricated by special oil. Insufficient lubrication or wear on parts can lead to inaccurate timekeeping or stoppage. Therefore, periodic checks are necessary.

Warranty and Repair

• For repairs or inspections, please contact the store where the watch was purchased or a SEIKO SERVICE CENTER.
• When seeking service within the warranty period, please present the warranty certificate.
• Warranty terms are detailed in the warranty certificate. Please read it carefully and keep it.

Troubleshooting

* For any other problems, please contact the store where the watch was purchased.

Accuracy of Mechanical Watches

The accuracy of mechanical watches is indicated by daily rates, typically averaged over a week.

The accuracy of mechanical watches may deviate from the specified range due to variations caused by usage conditions, such as wearing time, arm movement, and mainspring winding status.

The metal components in mechanical watches expand or contract with temperature changes, affecting accuracy. Mechanical watches may run slower in high temperatures and faster in low temperatures.

To maintain accuracy, it is crucial to regularly supply energy to the balance wheel, which regulates the timekeeping mechanism. The driving force from the mainspring, which powers the mechanical watch, is not uniform when the spring is fully wound versus partially wound. A less wound mainspring provides less driving force.

Consistent accuracy can be achieved by wearing the watch regularly for automatic models, and by fully winding the mainspring daily at the same time for manual winding models.

If the watch is exposed to a strong external magnetic field, mechanical watches may temporarily gain or lose time. Parts of the watch may become magnetized depending on the strength of the magnetic field. In such cases, consult the store where the watch was purchased, as the watch may require repair, including demagnetization.

Specifications

1. Dial

• Caliber 6R20/6R21/6R24: 6 hands: hour, minute, second hands; day of the week indicator; date indicator; power reserve indicator.
• Caliber 6R27: 5 hands: hour, minute, second hands; date indicator; power reserve indicator.

2. Vibrations per hour:

28,800

3. Accuracy (per day):

+25 to -15 seconds (between 5°C and 35°C)

4. Continuous operation time:

Not less than 45 hours

5. Drive type:

Automatic, with manual winding capability

6. Jewel count:

• Caliber 6R20/6R21/6R27: 29 jewels
• Caliber 6R24: 31 jewels

* The accuracy specified above is set at the factory.

** According to the characteristics of mechanical watches, actual accuracy may fall outside the specified range depending on usage conditions such as wearing time, temperature, arm movement, mainspring winding status, etc.