Component record · Train
Centre-Seconds Pinion
VerifiedA pinion (and its associated friction-driven or indirectly geared wheel) that carries a seconds hand mounted concentrically with the hour and minute hands at the centre of the dial.
What it does
Delivers a one-revolution-per-minute drive to a centrally mounted seconds hand, as an alternative to a small subsidiary seconds dial driven directly off the fourth wheel.
How it works
In an 'indirect' centre-seconds arrangement, common in wristwatches, a separate small wheel is friction-driven from the fourth wheel pinion and, in turn, friction-drives a pipe carried up through a hollow centre arbor to the dial side, where it carries the seconds hand.
The friction coupling in an indirect system deliberately allows some slip, both to permit hacking (stopping) the seconds hand for time-setting in hacking movements, and to absorb the small backlash that would otherwise make a swept seconds hand visibly judder.
A 'direct' centre-seconds arrangement instead routes the fourth wheel's own arbor through the centre, avoiding the friction coupling but requiring a specific train layout to bring the fourth wheel to the centre position.
Evolution
Subsidiary (off-centre) seconds dials were standard in earlier pocket watches and many mid-century wristwatches; sweep centre-seconds became progressively more popular through the 20th century, particularly after the rise of the wristwatch as an instrument for reading time at a glance, and became near-universal with quartz and many mechanical calibres.
Known variations
- Indirect (friction-driven) centre seconds
- Direct centre seconds
- Hacking centre-seconds mechanisms that stop the hand for precise time-setting
Identification for collectors
- A watch with a sweeping seconds hand emerging from the same centre point as the hour and minute hands, rather than a small subsidiary dial
Common failure modes
- Worn or contaminated friction coupling causing the seconds hand to stutter or lag (indirect systems)
- Bent centre-seconds pipe fouling the hour or minute hand
- Loose seconds hand from insufficient friction grip
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.