Grand Seiko: A Constant Force in Watchmaking

This article is from the WatchTime Archives and was originally published in 2022.

During the past six decades, Grand Seiko has constantly been pursuing the creation of the world’s most accurate wristwatch, pushing the development of quartz, mechanical and Spring Drive movements. Now, the Japanese
giant is ready to finally enter the haute horlogerie segment.

The T0 is Grand Seiko’s first constant-force tourbillon movement.

In September 2020, Seiko Watch Corporation revealed the T-zero Constant-force Tourbillon (abbreviated as “T0”) as a concept creation of Grand Seiko. It is the world’s first watch movement with a fully integrated constant-force mechanism and a tourbillon on the same axis, aiming to create a mechanical watch with the highest accuracy (and prestige) possible. The constant-force mechanism provides an even energy distribution to the escapement, regardless of how much the mainspring is wound, and the tourbillon aims to eliminate the error in precision caused by gravity by incorporating the escapement parts and balance in a rotating carriage.

The T0 obviously isn’t the first tourbillon from Seiko —that would be the Credor Fugaku tourbillon from 2016. Nor is it the first wristwatch to combine a remontoire and a tourbillon (with F.P. Journe most likely having made the first), but this undoubtedly is a first for Grand Seiko, and the brand claims that this is the only time a remontoire and a tourbillon have been brought together on the same axis. In most cases, when a constant-force mechanism is added, it is usually placed away from the carriage. Here, however, the T0 stores torque from a gear co-axially arranged with the carriage in a constant-force spring, and the energy of the unwinding spring is used for rotating the carriage, including the balance in it. Under laboratory conditions, the performance of the T0 over the duration of its 50-hour power reserve already indicated that the team of Takuma Kawauchiya, the movement’s designer and watchmaker at Seiko Instruments Inc., was successful with this choice of design: the T0 showed an incredible ±0.5 seconds maximum deviation in rate per day.

Kawauchiya also took a different approach in manufacturing the T0’s gears: to ensure even higher precision than traditional machining, he used a manufacturing process called Micro Electro Mechanical Systems (MEMS), a forming technique normally used for semiconductors. With this technique, metal films are layered like plating to materialize a perfect gear-tooth shape with precision measuring in microns. The same process has already been utilized in Grand Seiko’s pallet fork and escapement wheel, but this is the first time for the company to apply MEMS technologies to almost all gears. For the stop wheel, a ceramic gear was chosen to offer both high durability and low friction. Another specialty of the movement: While the inner tourbillon carriage (made of blued titanium) is rotating, the outer carriage is stopped by the engagement of the stopper and the stop wheel, resulting in a deadbeat motion of the second hand.

The T0 was developed over a five-year period; hand finishing alone took three months. The new caliber offers a 50-hour power reserve using two mainspring barrels, which run in parallel. The T0 measures 36 mm in diameter and 8.22 mm in height (with the tourbillon); the total parts count is 340 components. Surprisingly, the movement is actually based on the Grand Seiko Caliber 9S65, the brand’s “most standard automatic movement that typifies the 9S mechanical series.” The balance wheel therefore oscillates at 4 Hz (28,800 vph), which has become a standard for modern mechanical watches, but not necessarily for those with a remontoire and tourbillon. Still in the concept stage, the T0 is currently not used for a production model. But with the 220th birthday of the tourbillon coming up next year (the mechanism was patented on June 26, 1801 by Abraham-Louis Breguet), it would be surprising to not see a Grand Seiko of some sorts, sporting a “whirlwind” to increase accuracy, which has always been the mechanism’s main goal.

The SBGR321 is limited to 2,500 pieces, priced in the U.S. at $5,200.

A New Dawn
The 9S65 can also be found in one of the brand’s latest limited-edition watches, made in celebration of Grand Seiko’s 60th anniversary: the Grand Seiko Ref. SBGR321. The release of this watch follows the opening of Grand Seiko Studio Shizukuishi last July, a high-end watch and movement manufacturing site of Morioka Seiko Instruments (located in the town of Shizukuishi in Iwate Prefecture), “devoted to producing Grand Seiko mechanical watches and other high-end timepieces.” Its deep blue dial is inspired by “the brilliant blue sky over Mt. Iwate at dawn that greets the watchmakers and technicians of the Grand Seiko Studio Shizukuishi.”

The watch has a 40-mm-diameter stainless-steel case and a matching steel link bracelet with a push-button- release three-fold clasp. The case is water resistant to 100 meters and magnetic-resistant to 4,800 A/m. The movement, which is visible through a sapphire caseback, is assembled, adjusted, and inspected by hand at said new studio; it is adjusted to a daily rate accuracy from +5 to -3 seconds per day, beats at 28,800 vph, and stores a power reserve of 72 hours. The SBGR321 is limited to 2,500 pieces, priced in the U.S. at $5,200.

The Grand Seiko Caliber 9S65 is visible through the caseback.

Technically more demanding was the development of the new Grand Seiko Hi-Beat Caliber 9SA5 earlier this year: the latest evolution of the brand’s 9S mechanical caliber (first introduced in 1998) combines a 36,000-vph frequency with a lengthy 80-hour power reserve. Adjusted to a precision rate of +5 to -3 seconds per day, the new movement benefits from three technical features. The first is an in-house-developed dual-impulse escapement, in which the wheel transmits power directly to the balance for increased efficiency. Next in line is a newly developed free sprung balance that is more resistant to shock and friction than its predecessor and uses an overcoil rather than a flat hairspring to improve isochronism. Finally, Caliber 9SA5’s innovative, horizontal gear train allows the overall movement to be 15 percent slimmer than existing Grand Seiko Hi-Beat calibers.

The new movement made its debut in a limited-edition timepiece (100 pieces) that is based on the very first Grand Seiko watch of 1960. The 18k yellow-gold case of the Ref. SLGH002 measures 40 mm in diameter and features slightly wider lugs. The watch retails for $43,000.

The Ref. SLGH002 in yellow gold, limited to 100 pieces

Simultaneously, Grand Seiko has also been working on its Spring Drive calibers (first introduced in 1999). The new 9RA5 takes the brand’s proprietary technology literally to the next level: a power reserve of five days (a 60-percent increase), an even higher monthly precision rate of +/-10 seconds per month, and even a reduction in thickness, from 5.8 mm to 5 mm. This movement first debuted in the Grand Seiko Ref. SLGA001 dive watch. Water resistant to a professional-grade 600 meters, the 46.9-mm case in high-intensity titanium is mounted on a metal bracelet with a three-fold clasp, along with an interchangeable blue silicone strap. The watch is limited to 700 pieces and priced around $11,100. This model has already been nominated in the Diver’s category of the 2020 edition of the Grand Prix d’Horlogerie de Genève (GPHG).

A Dedication to Accuracy
While most of the Swiss high-end brands have focused on mechanical movements in the past three decades, the inventor of the world’s first quartz watch (introduced on Dec. 25, 1969), has never stopped pushing quartz technology further. Grand Seiko’s 60th anniversary is therefore also celebrated with the introduction of a new quartz movement. Caliber 9F85 has a time difference adjustment function that allows the hour hand to be adjusted without stopping the seconds hand and thus preserving its high precision. (In the SBGP007, the movement is adjusted to ±5 seconds per year; in the SBGP015 it is ±10 — as a comparison, Longines also offers an accuracy of ± 5 seconds per year with the Conquest V.H.P.) This new caliber makes its debut in two 60th anniversary designs. One of them, the SBGP015 with blue dial and a ceramic bezel of the same color offers a 20-bar water resistance, magnetic resistance of 16,000 A/m and a screw-down crown for enhanced security. It is available as a limited edition of 2,000 pieces and priced at $3,800.

Grand Seiko SBGP015 - angle
Grand Seiko Ref. SBGP015 has a blue dial and blue ceramic bezel.

Grand Seiko USA President Brice Le Troadec recently summed it up, saying, “Grand Seiko is now renowned for its three categories of calibers: Mechanical (including Hi-Beat), Spring Drive and Quartz. In the U.S., our sales are evenly shared between 9R Spring Drive-powered watches and 9S mechanical. Spring Drive offers an excellent alternative to those who really care for a fine mechanical movement, but want the precision of a quartz watch.”

The year 2020 saw the opening of the Grand Seiko Studio Shizukuishi (above) and a new boutique in Paris.

Perhaps one of the most fascinating things about Grand Seiko is that the Japanese watchmaker never lost sight of what ultimately has always been the main objective of a watchmaker: accuracy. Needless to say, watchmaking is part science, part art, especially in times when more and more people prefer to carry a computer on their wrist with twice the processing power of the Cray-2 (the fastest machine in the world when it was released in 1985). But the very essence of watchmaking is and has been about telling the time as accurately as possible. If it just becomes l’art pour l’art, the whole industry is at risk of losing its soul and its original purpose. When Greubel Forsey, for example, launched its first creation in 2004, the Double Tourbillon 30°, the two inventor-watchmakers wanted to increase the accuracy of mechanical timepieces. It was not about adding two tourbillons for the sake of adding two tourbillons. F.P. Journe’s Chronomètre à Résonance is, first and foremost, a chronometer. With the T0, Grand Seiko has demonstrated once again that it has never lost sight of the principles it was founded on 60 years ago, but the brand now covers almost every aspect of what might be best described as meaningful high-end watchmaking.

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  1. Thomas Cain

    I have a a259 5019 serial # 940594 missing a 12mm battery cover and gasket could anyone heip obtain these items?

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