Component record · Power
Barrel Cover
Partially verifiedThe removable lid closing a mainspring barrel.
What it does
Retains the coiled mainspring and its lubricant inside the barrel drum.
How it works
The cover snaps into a groove machined in the barrel wall, holding the spring in place while allowing service access.
Its inner face forms one of the two surfaces the spring bears against, so it is lubricated along with the barrel wall.
Evolution
Unchanged in principle; modern covers are stamped to tighter tolerances than early hand-finished examples.
Known variations
- Snap-fit cover
- Screwed cover in some clock barrels
Identification for collectors
- A distorted cover sits proud of the barrel rim.
- Bright rub marks inside indicate a spring running dry.
Common failure modes
- Distortion from careless prising
- Loose fit allowing the cover to lift
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.