# Barrel (cylindrical) cam with pin follower

> How does a barrel cam make reciprocating motion?

- Category: Mechanisms › Cams
- Kind: Hardware
- Basis: Xem Studio drawing; classic mechanism (Brown No. 106)
- Page: https://xemstudio.com/objects/barrel-cam-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=barrel-cam-mechanism · Plain text: https://xemstudio.com/objects/barrel-cam-mechanism/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

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

## Notes

- A groove cut round a cylinder carries a follower pin: one turn moves the pin along the axis by the groove's rise and back. Here a sine groove gives 15 mm of simple-harmonic stroke.
- Groove shape sets the motion: a helix reversed at the ends gives uniform speed (Brown's grooved cylinder), a sine gives smooth harmonic motion.
- Used in sewing machines, fishing reels' level wind and indexing tables.
- Parts (each has its own page): barrel-cam-r20-h15, dowel-pins-metric. Brown's movement No. 106 shows it (1868).

## Sizes

| parameter | value |
|---|---|
| cylinder | Ø40 × 50 mm |
| stroke | 15 mm |
| groove width | 6.4 mm (Ø6 pin) |

## 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

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/barrel-cam-mechanism/index.json

- barrel-cam-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/barrel-cam-mechanism/barrel-cam-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/barrel-cam-mechanism/barrel-cam-mechanism-assembly.stl) — Assembled mechanism, all parts placed (STEP keeps each part separate)

## Questions

**How does a barrel cam make reciprocating motion?**

A groove cut round a cylinder carries a follower pin: one turn moves the pin along the axis by the groove's rise and back. Here a sine groove gives 15 mm of simple-harmonic stroke.

## Fits with

- [Barrel (cylindrical) cam Ø40, 15 mm stroke](https://xemstudio.com/objects/barrel-cam-r20-h15/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)