# Elliptical gear, module 1.5, 36 teeth, b/a = 0.75, bore at the centre

> What is a centre-pivoted elliptical gear for?

- Category: Mechanisms › Gears
- Kind: Modern device
- Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
- Page: https://xemstudio.com/objects/elliptical-gear-m1-5-36t-centre-bore/ · JSON: https://xemstudio.com/api/geometry?object=elliptical-gear-m1-5-36t-centre-bore · Plain text: https://xemstudio.com/objects/elliptical-gear-m1-5-36t-centre-bore/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 |
|---|---|---|
| 64.18 | 48.97 | 12.0 |

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

## Notes

- Pitch ellipse 61.4 × 46.05 mm (perimeter 36 × π × 1.5) with the Ø8 bore at its centre; teeth generated by a 20° basic rack rolled round the pitch curve (spline outline within 0.008 mm), so it meshes with any module 1.5 involute pinion whose centre is free to follow the curve.
- Turning on its centre, its pitch radius at the mesh swings between the semi-axes twice per turn; the pinion must be free to move in and out to stay in mesh. 12 mm face.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| module | 1.5 |
| teeth | 36 |
| pitch ellipse | 61.4 × 46.05 mm |
| bore | Ø8 at the centre |
| face | 12 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. 35: figure, his text and an animation](https://507movements.com/mm_035.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/elliptical-gear-pinion-slotted-bar-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/elliptical-gear-m1-5-36t-centre-bore/index.json · license: https://xemstudio.com/files/hardware/elliptical-gear-m1-5-36t-centre-bore/LICENSE.md

- elliptical-gear-m1-5-36t-centre-bore: [STEP](https://xemstudio.com/files/hardware/elliptical-gear-m1-5-36t-centre-bore/elliptical-gear-m1-5-36t-centre-bore.step) · [STL](https://xemstudio.com/files/hardware/elliptical-gear-m1-5-36t-centre-bore/elliptical-gear-m1-5-36t-centre-bore.stl) — gear, centre on the Z axis, major axis along X, z 0..12

## Questions

**What is a centre-pivoted elliptical gear for?**

Pitch ellipse 61.4 × 46.05 mm (perimeter 36 × π × 1.5) with the Ø8 bore at its centre; teeth generated by a 20° basic rack rolled round the pitch curve (spline outline within 0.008 mm), so it meshes with any module 1.5 involute pinion whose centre is free to follow the curve.

## Fits with

- [Elliptical gear driving a pinion whose shaft slides in a slotted bar](https://xemstudio.com/objects/elliptical-gear-pinion-slotted-bar-mechanism/)