What Makes the Grand Seiko 9S86 Movement So Special? A Technical Overview

The Grand Seiko 9S86 movement is a mechanical movement that can be wound automatically by the motion of the wearer’s wrist or manually by turning the crown. It has a high-beat frequency of 10 beats per second, which means that it oscillates 36,000 times per hour. This gives it a higher accuracy and stability than most mechanical movements, which usually oscillate at 6 or 8 beats per second. The movement also has a GMT function, which means that it can display two time zones at the same time. The GMT hand shows the time in the home time zone, while the hour hand can be adjusted to show the local time. The movement has a date window at 3 o’clock position and a power reserve of about 55 hours.


Features and Specifications


The following table summarizes the main features and specifications of the Grand Seiko 9S86 movement:


  • Winding mechanism: Automatic with manual winding capability
  • Display: Analog with date window
  • Diameter: 28.4 mm
  • Thickness: 6.5 mm
  • Jewels: 37
  • Power reserve: Approximately 55 hours
  • Frequency: 36,000 vibrations per hour (10 beats per second)
  • Accuracy: -5 to +3 seconds per day (when static)
  • Functions: Hours, minutes, seconds, date, GMT





GMT Function


The GMT function allows the user to keep track of two time zones simultaneously. This is useful for travelers who need to know the time in their home country and their destination country.

The GMT hand is a fourth hand that rotates once every 24 hours and points to a 24-hour scale on the bezel or the dial. The GMT hand shows the time in the home time zone, which is usually set to the user’s country of origin.

The hour hand can be adjusted independently to show the local time, which is usually set to the user’s current location. The hour hand can be moved in one-hour increments by pulling out the crown by one notch and turning it clockwise or counterclockwise.

The date will change accordingly when the hour hand passes midnight. The second hand will continue to run during this operation, so that the accuracy of the movement is not compromised.

To adjust the home time, the user can pull out the crown by two notches and turn it clockwise or counterclockwise to move both the hour hand and the GMT hand in sync. The date will not change during this operation.





High-Beat Technology


The high-beat frequency of 36,000 vibrations per hour (10 beats per second) gives the movement a higher precision and stability than conventional mechanical movements that beat at 21,600 or 28,800 vibrations per hour (6 or 8 beats per second). The high-beat frequency also results in a smoother sweep of the second hand, creating a more refined visual impression. To achieve such a high frequency, Grand Seiko has developed several innovations, such as:


• A redesigned hairspring that is thinner and more resistant to shock and magnetism. The hairspring is made of a special alloy called Spron 610, which was developed by Grand Seiko’s parent company Seiko Instruments Inc. The hairspring regulates the oscillation of the balance wheel, which controls the accuracy of the movement.







• A redesigned mainspring that provides more torque and longer power reserve. The mainspring is made of another special alloy called Spron 530, which was also developed by Seiko Instruments Inc. The mainspring stores the energy that powers the movement.





• A MEMS (Micro Electro Mechanical Systems) technology that allows for more precise and lightweight components. MEMS is a process that uses semiconductor manufacturing techniques to create microscopic parts with high accuracy and durability. Grand Seiko uses MEMS to produce parts such as the escapement wheel, pallet fork and lever, which are essential for transferring energy from the mainspring to the balance wheel. • A special lubricant that reduces friction and wear. Grand Seiko uses a synthetic oil that has a low viscosity and a high resistance to temperature changes. The lubricant ensures that the movement runs smoothly and reliably.











The Grand Seiko 9S86 movement is used in SBGJ Family of Grand Seiko watches.

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