# Constant-breadth cam: rounded Reuleaux triangle, breadth 40, Ø5 bore at its centre

> What is a constant-breadth cam?

- Category: Hardware › Mechanism parts
- Kind: Modern device
- Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
- Page: https://xemstudio.com/objects/constant-breadth-cam-s30-r5-bore5/ · JSON: https://xemstudio.com/api/geometry?object=constant-breadth-cam-s30-r5-bore5 · Plain text: https://xemstudio.com/objects/constant-breadth-cam-s30-r5-bore5/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 |
|---|---|---|
| 40.0 | 40.0 | 8.0 |

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

## Notes

- Reuleaux triangle of side 30 (three arcs of R30 about the opposite corners) with every edge offset 5 mm, so the corners are R5 arcs: breadth 40 mm in every direction. Bored Ø5 at its centre: turning there inside a yoke 40 mm wide it always touches both faces and moves the yoke 4.64 mm, three times per turn.
- Corner (vertex arc centres) on a 17.32 mm circle; largest radius 22.32 mm, smallest 17.68 mm.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| breadth | 40 mm |
| Reuleaux side | 30 mm |
| corner radius | 5 mm |
| thickness | 8 mm |
| bore | Ø5 at the centre |

## 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. 276: figure, his text and an animation](https://507movements.com/mm_276.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/constant-breadth-cam-yoke-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/constant-breadth-cam-s30-r5-bore5/index.json · license: https://xemstudio.com/files/hardware/constant-breadth-cam-s30-r5-bore5/LICENSE.md

- constant-breadth-cam-s30-r5: [STEP](https://xemstudio.com/files/hardware/constant-breadth-cam-s30-r5-bore5/constant-breadth-cam-s30-r5.step) · [STL](https://xemstudio.com/files/hardware/constant-breadth-cam-s30-r5-bore5/constant-breadth-cam-s30-r5.stl) — cam, z 0..8, a corner on +Y

## Questions

**What is a constant-breadth cam?**

Reuleaux triangle of side 30 (three arcs of R30 about the opposite corners) with every edge offset 5 mm, so the corners are R5 arcs: breadth 40 mm in every direction. Bored Ø5 at its centre: turning there inside a yoke 40 mm wide it always touches both faces and moves the yoke 4.64 mm, three times per turn.

## Fits with

- [Constant-breadth cam turning in a yoke (three strokes per turn)](https://xemstudio.com/objects/constant-breadth-cam-yoke-mechanism/)