--Orders are currently shipped by DHL(Free shipping) -- Due to EMS postal service delays --
0 Cart
Added to Cart
    You have items in your cart
    You have 1 item in your cart

      SeiyaJapan blog

      A way to rebirth of Seiko’s mechanical watches Vol.2/ 4S movement

      A way to rebirth of Seiko’s mechanical watches Vol.2/ 4S movement

      Summarized and translated the article, “A way to rebirth of Seiko’s mechanical watches”
      (p.5-9, GS9 "Grand Seiko Magazine / Grand Seiko Nine" TWO, March 2015) 

      Production of the new 4S caliber

      Seiko formed an in-house mechanical watch project team due to the
      positive response received from the 6810 UTD series.
      But no engineer with experience in mechanical caliber design was
      available in a company.

      So, the new caliber, 4S35 was decided to manufacture based on the old
      52 caliber, which was produced 20 years ago.
      The 52 caliber prided itself on precision of the 1970’s Chronometer standard.

      At last, 200,000 4S calibers were produced. Seiko understood it was
      too many. However, manufacturing new caliber costs a lot. Seiko had to
      make 200, 000 calibers.

      The first watch fitted with the 4S was on sale at the end of 1992.
      It was SCVK001 (4S35-8000) with 4S35 caliber.

      Mechanical watches became the focus of attention in the media.
      This boosted Grand Seiko’s mechanical type revival.

      Tanaka wanted to create new Grand Seiko with new high-end caliber. But
      because there were too many 4S caliber surplus, company didn't want to
      develop new caliber.

      As Seiko had to keep to use 4S calibers, they made mechanical watches
      like "Credor Chronometers GBAY992”,  "KING SEIKO 2000 repro model", Laurel, and SUS with 4S calibers.

      Grand Seiko’s mechanical type revival

      Some years later, Seiko began to produce new Grand Seiko with new
      mechanical caliber. It was 1996.

      A young engineer, Jujo Kouichiro tried to fine-tune 4S calibers for new Grand
      Seiko first. But he soon understood it was impossible. Because Grand
      Seiko needs more precision accuracy.

      Each and every retired technical expert was interviewed in order to
      form the new movement.
      Many test products were developed by utilizing 3D CAD computer
      technology. The precision and structure of the test products were
      redone over and over again by ”Ohira Akira”, allowing the completely new movement to be
      completed in just 2 short years.
      (Please search ”Ohira Akira” by Google) 

      The Grand Seiko SBGR001 mechanical type was revived on November 27, 1998.


      Citizen watch instructions are available online only


      I have an announcement to make.

      Citizen has ceased to provide instructions for their wristwatch lineup.

      Their instructions have been made available online.

      They are available in English, French, Spanish, German, Italian, Portuguese, and Chinese.

      They can be printed,  but it will use up a lot of paper, so please print only the necessary pages.



      About the OCW-T200 series Mobile Link "Oceanus Connected"

      The OCW-T200 easily connects to your smartphone via Bluetooth where you can check the information available on Oceanus.


      Top screen


      History of Self Adjustment

      You can view its history of self adjustment records to view time zone corrections via radio waves and Bluetooth.



       Solar Power Charging Transition

      The amount of energy generated by the solar cell of the watch is displayed.


      Latest Updates

      It updates with the latest time zone and summer time information from each country.

      Phone finder 

      It searches for your smartphone.

      Tuna can / Next generation model

      Tuna can / Next generation model

      Out of production model


      Next generation model


      SBDX038 /1000m 8L35 Automatic Movement

      • Listed price about 4000US$
      • Aug 2020 release
      • The bezel is made using "Ever-brilliant steel" (EBRSS), giving the surface a sense of world-class durability and beauty.


      Left -- SBBN047  1000m 7C46 Quartz Movement 

      • Listed price about 2500US$
      • Jul 2020 release
      • The SBBN047 is made even more scratch resistant due to the shroud and bezel being finished with "Super black dia-shield"

      Right  -- SBBN045   300m 7C46 Quartz Movement  

      • Listed price about 1500 US$
      • Jul 2020 release
      • The SBBN045 is finished by dia-shield on the shroud
      Uniform upgrade 
      • There is an arrow tip on the minute hand to make it easily visible when underwater.
      • The indexes have been triangulated and rounded, which increases visibility even more.


      About the Quartz watch Second hand alignment

      About the Quartz watch Second hand alignment

       About the Quartz watch Second hand alignment

      There are times when the second hand doesn’t quite hit the marker.second hand mis-alignment

      I have received many questions regarding this from several customers asking why this was happening. I found an easy-to-understand explanation on the Citizen watch site, so I am posting a summary of it. 

      The second hand’s movement is controlled by the gears. There is an intentional space placed in-between each gear.  That space(playfully) is called "backlash". This backlash is the cause of the second hand mis-alignment The gear space causes the place where the second hand stops to slip a little.

       An adequate backlash is essential for smooth gear operation. To put it quite simply, the gears would stop turning if the backlash was too small.

      The reasons for the necessity of an adequate backlash are outlined below. 

      1.Thermal expansion
      The gears expand due to the heat from friction. A difference of just 10C can have an affect on gear alignment, even if they are small. The backlash is essential in minimizing that affect. 

      2.  Distortion
      The gears of a watch take on pressure as they mov, causing these small parts to become slightly distorted. The backlash is necessary to minimize distortion.

       3. Impact
      Watches are sometimes dropped. The will cause the gears to break upon direct impact if there isn’t a bit of slack. 

       4. Wear resistance
      By creating a backlash, it is easier for lubricant to get up into the gearspreventing abrasion. 

      5.Parts Standardization
      The parts in a watch are not all exactly the same size, strictly due to error, despite an increase in machining accuracy.(Of course this is within the acceptable range for the maker).In order to account for this error, it is important to put the backlash into place to ensure that all parts turn smoothly..
      This might be the main reason.

      In conclusion

      The Backlash is an essential part of the gear, and can’t be removed 100%.

      While it is possible to reduce the backlash by improving the gear manufacturing precision and assembly method, doing so would have an impact on thermal expansion, impact, and wear resistance etc.

      In other words, an adequate backlash is the solution for balancing durability, accuracy, and refined hand movement within the watch.

      That is all of the available information from the Citizen watch site.

      Citizen watch site (Japanses)
      Picture : Wikipedia

      The rest is what I have been able to determine speaking from personal experience.

      SEIKO has come out with Backlash auto-adjust mechanism, which they use in the Grand Seiko Quartz for reducing second hand mis-alignment.

      The Grand Seiko Quartz uses the power of the spring to reduce the slight second hand  mis-alignment that is created by the backlash as much as possible. (It’s like stopping the motion of a moving object with the power of a spring, which is difficult to wrap my head around.)

      Even though the misalignment is far less noticeable in Grand Seiko is n comparison to any other watch, even the meticulously crafted Grand Seiko suffers from a slight second hand mis-alignment. (Sorry SEIKO)

      About SEIKO Backlash auto-adjust mechanism,

      Seiya Kobayashi