Component record · Power
Barrel Arbor Hook
Partially verifiedThe hook or slot on the barrel arbor engaging the mainspring's inner end.
What it does
Anchors the inner coil of the mainspring so winding the arbor tightens the spring.
How it works
The inner eye of the spring engages the hook, so arbor rotation coils the spring inward.
A worn hook lets the spring slip, giving a watch that winds without gaining power.
Evolution
Hook geometry became standardised as springs were industrially produced.
Known variations
- Hooked arbor
- Slotted arbor
Identification for collectors
- Winding with no build-up of resistance suggests a slipping inner attachment.
- Inspection requires the barrel to be opened by a watchmaker.
Common failure modes
- Worn hook
- Broken spring eye
Related photographs
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- de Carle, D., Practical Watch Repairing
- de Carle, D., Watch and Clock Encyclopedia
- Daniels, G., Watchmaking
Where sources disagree, the disagreement is stated rather than resolved silently.