Component record · Power
Maltese Cross
VerifiedA five-pointed star-shaped wheel, one point of which is solid rather than slotted, used as the indexing element of Geneva-style stopwork.
What it does
Provides the mechanical limit stop within stopwork by physically blocking the driving finger once the barrel has been wound or run down to its permitted extreme.
How it works
Four of the cross's five points are cut with a slot that lets the barrel's finger index the cross by one point per barrel revolution, in the manner of a Geneva drive mechanism used elsewhere in machinery for intermittent motion.
The fifth point is left solid; when the finger arrives at this point it cannot pass, arresting further rotation in that direction and thereby setting the limit on winding or unwinding.
Because the mechanism only allows a fixed number of index steps in each direction, it defines exactly how many turns of the mainspring barrel are usable before winding is physically prevented.
Evolution
The same Geneva-drive geometry used in stopwork is a general mechanical-engineering solution for intermittent indexing and predates its specific watchmaking application.
Known variations
- Five-pointed cross (most common in watch stopwork)
- Alternative tooth counts used in some clock stopwork designs
Identification for collectors
- Recognisable star-wheel shape distinguishes it from ordinary round gear wheels in the movement
Common failure modes
- Chipped points from forced overwinding
- Wear at the slot edges causing looseness in indexing
Photographs
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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., Watch and Clock Encyclopedia
Where sources disagree, the disagreement is stated rather than resolved silently.