# Swing arm / link 30 mm, Ø3 hole one end, Ø6 the other

> What is this 30 mm arm?

- 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/swing-arm-30-holes-3-and-6/ · JSON: https://xemstudio.com/api/geometry?object=swing-arm-30-holes-3-and-6 · Plain text: https://xemstudio.com/objects/swing-arm-30-holes-3-and-6/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 | 10.0 | 5.0 |

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

## Notes

- 10 × 5 mm bar with a Ø3 hole and, 30 mm away, a Ø6 hole: used twice in the eccentric gear drive, as the arm that swings the pinion's Ø6 axle about a fixed Ø3 pin and as the link from the gear's Ø3 centre stud to that axle.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| centres | 30 mm |
| holes | Ø3 and Ø6 |
| section | 10 × 5 mm |

## 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. 222: figure, his text and an animation](https://507movements.com/mm_222.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/eccentric-gear-and-pinion-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/swing-arm-30-holes-3-and-6/index.json · license: https://xemstudio.com/files/hardware/swing-arm-30-holes-3-and-6/LICENSE.md

- swing-arm-30-holes-3-6: [STEP](https://xemstudio.com/files/hardware/swing-arm-30-holes-3-and-6/swing-arm-30-holes-3-6.step) · [STL](https://xemstudio.com/files/hardware/swing-arm-30-holes-3-and-6/swing-arm-30-holes-3-6.stl) — Ø3 at (−15, 0), Ø6 at (15, 0), z 0..5

## Questions

**What is this 30 mm arm?**

10 × 5 mm bar with a Ø3 hole and, 30 mm away, a Ø6 hole: used twice in the eccentric gear drive, as the arm that swings the pinion's Ø6 axle about a fixed Ø3 pin and as the link from the gear's Ø3 centre stud to that axle.

## Fits with

- [Eccentric spur gear and pinion on a swinging arm (variable speed)](https://xemstudio.com/objects/eccentric-gear-and-pinion-mechanism/)