Skeleton / Openwork
Movement plates cut away to reveal the mechanics
What it is
A skeleton or openwork movement has its bridges and main plate cut away to reveal the gear train, escapement, and other components to the viewer. The remaining material forms a structural web of pillars and arches that retains the mechanical integrity of the movement while exposing as much of the mechanism as possible. Skeleton movements are typically paired with an exhibition caseback; and often a transparent or open-worked dial; so the mechanism is visible from both sides.
History
Skeleton pocket watches were made in the 18th century for the same reason they are made now: to show the owner the mechanism inside. Breguet produced skeleton pocket watches; in the modern wristwatch era, Audemars Piguet's Royal Oak Squelette (openwork) is the most commercially significant example, carrying the AP price premium while removing material from the movement rather than adding it. Skeletonising is deceptively expensive because every new edge created by cutting the material must be chamfered and polished; more exposed edges means more finishing work per part, so removing material typically increases production cost.
How it works
Bridges and plates are cut using a jeweler's saw, CNC milling, or laser cutting to remove material between structural pillars, leaving a minimal framework. Every exposed edge created by the cutting operation must be chamfered (anglaged) and polished by hand; the quality of this edge finishing is the primary differentiator between a fine skeleton movement and a production-level one. Exhibition casebacks and sapphire crystal casebacks are standard additions to allow viewing.
Parts required
No additional components are required for the skeleton function itself; the existing bridges and plates are machined to remove material while retaining structural geometry. An exhibition caseback (typically sapphire) is added to the case.
In the catalog
Related
- Anglage: Beveling and polishing the edges of movement parts
- Mirror polishing: Producing an optically flat, reflective surface on steel
- Guilloché: Engine-turned geometric engraving on metal
