Component record · Keyless work
Winding Pinion
VerifiedA small, splined or square-bored pinion at the inner end of the winding stem that slides along the stem and engages the keyless winding train when the crown is turned for winding.
What it does
Transmits the crown's rotation into the winding train (via the intermediate or crown wheel to the ratchet wheel) when the stem is in its normal winding position, and disengages or is bypassed when the stem is pulled out for hand-setting.
How it works
The winding pinion has a squared or splined bore that engages a matching square or splines on the winding stem, so that it is carried around when the stem turns but can also slide axially along the stem as the setting lever repositions the stem between winding and setting positions.
In the winding position, the winding pinion meshes with the crown wheel (or an intermediate winding wheel, depending on the specific keyless-works layout), driving the ratchet wheel and winding the mainspring; in the setting position, the stem's motion is instead routed through the sliding pinion and setting/minute wheels to the motion work for hand-setting.
The switch between these two engagement states is what the setting lever, yoke and clutch lever/wheel assembly of the keyless works exist to control.
Evolution
Refined in detail across the many keyless-works patents of the later nineteenth century, but functionally stable as a concept since keyless winding became the near-universal standard, replacing separate key-wound arbors.
Known variations
- Winding pinion designs specific to a given manufacturer's keyless-works layout
- Combined winding/sliding pinion assemblies in some compact calibres
Identification for collectors
- Visible on the stem when the keyless works is exposed, as the toothed component nearest the crown end that meshes with the crown wheel when winding
Common failure modes
- Worn or rounded splines/square causing the pinion to slip on the stem rather than turning it positively
- Chipped teeth from forceful or careless winding
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- de Carle, D., Practical Watch Repairing
Where sources disagree, the disagreement is stated rather than resolved silently.