Component record · Power
Barrel Arbor
VerifiedThe central steel shaft running through the mainspring barrel, onto which the mainspring's inner coil is anchored.
What it does
Provides the axis about which the mainspring is coiled when wound, and transmits winding torque from the winding mechanism into the spring.
How it works
One end of the arbor is squared, slotted, or otherwise shaped to receive the winding key or the ratchet wheel of a keyless winding train.
The mainspring's inner coil is hooked or slipped onto a corresponding feature on the arbor, so turning the arbor coils the spring tighter during winding.
The arbor's pivots run in the plate and barrel bridge (or a cap jewel in finer work), and must be sufficiently robust to withstand the full winding torque without bending or excess friction.
Evolution
Little changed in basic principle across centuries of watchmaking, though pivot finishing and jeweling have improved to reduce friction and wear.
Known variations
- Square-ended arbor for key winding
- Arbor integrated with a ratchet wheel for keyless winding
- Arbors fitted with a hook versus a slipping-bridle attachment for the spring's inner coil
Identification for collectors
- Visible as the central shaft when a barrel is opened, distinguishable from the barrel body itself
Common failure modes
- Worn or rounded winding square
- Bent arbor from forced overwinding
- Worn pivots causing barrel wobble and poor meshing
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
Where sources disagree, the disagreement is stated rather than resolved silently.