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This is a genuine 6H second chronograph wheel designed for the MIYOTA 0S20 quartz chronograph movement, made in Japan and brand new. This gear is a critical transmission component in the chronograph module, located at the 6 o‘clock sub-dial position, responsible for transmitting chronograph power to the 60-minute or small seconds indicator for precise timing function. As an original factory part, it is the ideal choice for replacing worn components during service or repair.
MIYOTA 0S20 Technical Background :
| Parameter | Value |
|---|---|
| Movement Type | Quartz chronograph |
| Size | 13 1/2‴ (approx. 30.8 mm) |
| Height | 5.10 mm |
| Accuracy | ±20 seconds per month |
| Battery Life | 5 years |
| Battery | SR927W |
| Functions | Chronograph (min/sec), 24 hour, date |
| Sub-dial Layout | 3H: 24 hour / 6H: small seconds / 9H: chronograph minute |
| Normal Operation | Press button A (2 o‘clock) to start/stop chronograph; press button B (4 o’clock) to reset |
| Chronograph Reading | Center large seconds hand measures seconds; 9 o‘clock sub-dial measures minutes (up to 59:59); 6 o’clock indicates small seconds |
| Failure Symptoms | Worn 6H wheel causes: 6 o‘clock small seconds hand stops or jumps erratically; inaccurate chronograph minute display |
| Post-Battery Reset | If chronograph hands don’t reset after battery change, pull crown to 2nd position and press button A to zero hands |
| Step | Instruction |
|---|---|
| 1. Remove Movement | Open the case back and carefully remove the MIYOTA 0S20 movement |
| 2. Remove Hands | Carefully remove hour, minute, and all sub-dial hands |
| 3. Remove Dial | Remove the dial to expose the chronograph module |
| 4. Remove Old Gear | Carefully remove the old 6H chronograph wheel |
| 5. Cleaning | Clean the gear mounting area – remove debris |
| 6. Install New Gear | Place the new 6H wheel in position, ensuring proper gear meshing |
| 7. Assemble & Test | Reinstall dial and hands, then test chronograph function |
Important Note: The 0S20 chronograph module requires precise alignment. For hand reference, set crown to 2nd position (time setting), align hour/minute hands at 12, and center seconds hand at 0 . Professional installation by a watchmaker is recommended.
| Aspect | Guidance |
|---|---|
| Inspection Period | Check chronograph function during each battery change (approx. 5 years) |
| Wear Indicators | Worn 6H wheel causes: 6 o‘clock small seconds stops, uneven ticking, or inaccurate chronograph minute display |
| Common Issues | If chronograph fails, first check battery voltage; then inspect gear for sticking or wear |
| Battery Replacement | Use SR927W battery ; after replacement, check chronograph reset function |
| Cleaning Method | Use dust blower to clean movement surface; avoid liquid cleaners |
| Replacement Interval | Replace only when gear is damaged or wear significantly affects chronograph function |
Q1: What is the 6H chronograph wheel used for?
A: The 6H chronograph wheel drives the sub-dial at the 6 o‘clock position. The 0S20 movement’s 6H sub-dial typically indicates small seconds (running seconds), not the chronograph minutes .
Q2: Can I install this wheel myself?
A: This repair requires movement disassembly, careful handling of small parts, and experience with chronograph modules. Professional installation by a watchmaker is strongly recommended.
Q3: How do I reset the chronograph after replacing the battery?
A: Pull crown to 2nd position, press button A to move the chronograph seconds hand to zero, then push crown back. Do not return crown while hand is moving – it will stop midway and register the wrong zero position .
Q4: What are the hand dimensions for the 0S20?
A: According to technical specifications, hand dimensions are: hour 120, minute 70, seconds 17, sub-dial indicators 26 (in 1/100mm units) .
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