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The SEIKO (SII) NH35/NH36/NH37/NH38/NH39 Third Wheel (#0231070) is a genuine Japanese-made component for the popular NH series automatic movements. The third wheel is a critical part of the gear train, transmitting rotational power from the center wheel through the gear train to the second reduction wheel and fourth wheel, ultimately driving the hands with stable torque for accurate timekeeping. This brand new original part is essential for watchmakers restoring smooth power transmission and timekeeping accuracy when the original third wheel becomes worn or damaged.
Genuine Seiko/SII part – authentic Japanese-made component for NH35, NH36, NH37, NH38, and NH39 movements
Gear train component – transmits power from the center wheel to the second reduction wheel and fourth wheel
NH family compatibility – compatible across the most popular NH series calibers
Direct replacement – drop-in replacement for worn or damaged third wheels
Part Number: 0231070
Compatible Movements: Seiko NH35, NH36, NH37, NH38, NH39 (also known as 4R35/36/37/38/39)
Movement Family: NH Series (Basic Mechanical Series)
Movement Diameter: 27.4 mm
Movement Height: 5.32 mm
Jewels: 24
Frequency: 21,600 vph (3 Hz)
Power Reserve: >41 hours
Hacking: Yes
Hand-Winding: Yes
Origin: Japan
Service and overhaul – replacing worn or damaged third wheels in NH series movements
Gear train restoration – ensuring smooth power transmission and stable timekeeping
Suitable for professional watchmakers and experienced repair technicians
1. Is this a genuine Seiko/SII part?
Yes, this is a genuine Seiko (SII/TMI) factory part made in Japan. The NH series is manufactured by Seiko Instruments Inc. (SII) and distributed by Time Module Inc. (TMI). The NH prefix indicates the movement is sold without Seiko branding for use by third-party watch manufacturers and the mod community.
2. Which movements is this third wheel compatible with?
This third wheel is compatible with Seiko NH35, NH36, NH37, NH38, and NH39 movements. These are all based on the same NH35 architecture, with differences in complications (date, day-date, 24-hour indicator, open heart) . The gear train components are shared across these calibers.
3. What are the signs that the third wheel needs replacement?
Common signs include irregular timekeeping, low amplitude, or visible wear/damage to the teeth during movement inspection. The NH series has a factory accuracy specification of -20 to +40 seconds/day . A qualified watchmaker can diagnose these issues during servicing.
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