Identify index-regulated vs free-sprung balances and understand how each system is adjusted, plus what that means for timing behaviour and service.
| System | How rate is adjusted | Owner takeaway |
|---|---|---|
| Index regulator | Move regulator arm / curb pins | Common, efficient to regulate in service |
| Free-sprung | Adjust balance weights/screws | Often chosen for stability-focused designs |
Index-regulated movements change rate by altering the effective active length of the hairspring through a regulator assembly.
Free-sprung balances keep the hairspring free of an index and adjust rate by changing the balance’s effective inertia (screws/weights).
Index systems are common and practical to regulate. Free-sprung designs are often favoured where positional stability is a design priority.
• This is not a DIY adjustment feature
• Rate correction belongs to trained watchmakers
• “Free-sprung” does not automatically mean perfect accuracy forever
• Poor regulation or aged oils can hurt either system
What is an index regulator? A common regulation system where a movable index assembly changes the effective active length of the hairspring to adjust rate.
What is a free-sprung balance? A balance design without an index regulator, adjusted by changing balance inertia through screws or weights.
Is free-sprung always more accurate? Not automatically. It can support excellent stability, but overall movement quality and regulation still decide results.
Can I regulate my watch at home? No. Regulation requires proper tools, timing equipment and training.