# Geneva stop star: 5 positions, 4 slots and one convex stop tooth, Ø64.72, Ø5 bore

> What is the star of a Geneva stop?

- Category: Mechanisms › Intermittent motion
- Kind: Modern device
- Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
- Page: https://xemstudio.com/objects/geneva-stop-star-5-positions-4-slots-r32-4/ · JSON: https://xemstudio.com/api/geometry?object=geneva-stop-star-5-positions-4-slots-r32-4 · Plain text: https://xemstudio.com/objects/geneva-stop-star-5-positions-4-slots-r32-4/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 60.13 | 63.14 | 6.0 |

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Maltese cross of tip radius 32.36 (= a·cos(π/5)) with 5 positions 72° apart: 4 radial slots 4 wide (= the pin, no clearance) with round bottoms 17.87 mm deep, and one position left as a convex tooth of the full rim radius — the stop. Between positions the rim is a concave arc of radius 20.51 about the finger wheel's centre, which rests on the locking disc.
- Each turn of the finger wheel indexes the star one position; after four turns the pin arrives at the convex tooth, cannot enter, and the wheel is held: a four-turn stop. In a watch the finger wheel sits on the barrel arbor and the star on a stud — it limits the winding so the mainspring never reaches its stiffest, over-wound turns.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| positions | 5 (4 slots + 1 stop tooth) |
| tip radius | 32.36 mm |
| slot | 4 wide, 17.87 deep |
| locking arcs | r 20.51 about the wheel centre |
| thickness | 6 mm |
| bore | Ø5 |
| turns allowed | 4 |

## Where the files are

- Henry T. Brown (1868, public domain): [Five Hundred and Seven Mechanical Movements — scan on archive.org](https://archive.org/details/fivehundredseven00browiala) — web — Publisher's page; dimensions are facts
- 507movements.com: [Brown's movement No. 212: figure, his text and an animation](https://507movements.com/mm_212.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/geneva-stop-winding-stop-mechanism/) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/geneva-stop-star-5-positions-4-slots-r32-4/index.json · license: https://xemstudio.com/files/hardware/geneva-stop-star-5-positions-4-slots-r32-4/LICENSE.md

- geneva-stop-star-5-positions-4-slots-r32-4: [STEP](https://xemstudio.com/files/hardware/geneva-stop-star-5-positions-4-slots-r32-4/geneva-stop-star-5-positions-4-slots-r32-4.step) · [STL](https://xemstudio.com/files/hardware/geneva-stop-star-5-positions-4-slots-r32-4/geneva-stop-star-5-positions-4-slots-r32-4.stl) — star, axis Z, z 0..6, slot 0 on -X, stop tooth at 288°

## Questions

**What is the star of a Geneva stop?**

Maltese cross of tip radius 32.36 (= a·cos(π/5)) with 5 positions 72° apart: 4 radial slots 4 wide (= the pin, no clearance) with round bottoms 17.87 mm deep, and one position left as a convex tooth of the full rim radius — the stop. Between positions the rim is a concave arc of radius 20.51 about the finger wheel's centre, which rests on the locking disc.

## Fits with

- [Geneva stop (Maltese cross stop-work): finger wheel limited to four turns](https://xemstudio.com/objects/geneva-stop-winding-stop-mechanism/)