SEIKO (SII) NH05/NH06 Fourth Wheel

Product Description

The SEIKO (SII) NH05/NH06 Fourth Wheel is a genuine Japanese-made component for these compact automatic movements, measuring 7¾”’ (approx. 17.5mm) in diameter . As a key part of the gear train, the fourth wheel transmits power from the third wheel to the escape wheel and pallet fork, playing a critical role in regulating the movement’s timekeeping accuracy. This brand new original part is essential for watchmakers restoring proper power transmission and timekeeping function when the original gear train component becomes worn or damaged.

Features & Function

• Genuine Seiko/SII part – authentic Japanese-made component for NH05 and NH06 movements

• Gear train component – transmits power from the third wheel to the escape wheel and pallet fork for accurate timekeeping

• 21-jewel movement – part of the 21-jewel NH0 series architecture 

• NH0 family compatibility – designed for the compact 7¾”’ NH05 (date) and NH06 (day-date) calibers 

Specifications

• Compatible Movements: Seiko NH05 (date), NH06 (day-date)

• Movement Family: NH0 Series

• Movement Size: 7¾”’ (approx. 17.5mm) 

• Movement Height: 5.92mm 

• Jewels: 21 

• Frequency: 21,600 vph (3 Hz) 

• Power Reserve: >40 hours 

• Crown Positions: Normal (manual winding), 1st click (date/day setting), 2nd click (time setting) 

• Origin: Japan

Applications

• Service and overhaul – replacing worn or damaged fourth wheels in NH05/NH06 movements

• Gear train restoration – ensuring stable power delivery to the escapement for accurate timekeeping

• Suitable for professional watchmakers and experienced repair technicians

FAQs

1. Is this a genuine Seiko/SII part?

Yes, this is a genuine Seiko (SII/TMI) factory part made in Japan. The NH05 and NH06 are manufactured by Seiko Instruments Inc. (SII) and distributed by Time Module Inc. (TMI) .

2. Which movements is this fourth wheel compatible with?

This fourth wheel is designed for Seiko NH05 and NH06 movements. The NH05 features a date display, while the NH06 adds a day-date complication, but both share the same basic gear train architecture .

3. What are the signs that the fourth wheel needs replacement?

Common signs include worn or damaged teeth, irregular timekeeping, low amplitude, or visible wear during movement inspection. A qualified watchmaker can diagnose these issues during servicing.

Why Choose SOFLY Watch Parts?

• Fast worldwide shipping within 3 business days.

• Competitive pricing on Seiko/Hattori calibers.

• 3,000+ watch movements and parts in stock.

• Trusted by watchmakers worldwide.

• Personalized sourcing support via [email protected] or WhatsApp +86 18620212114.