# Gear rack, module 1, 120 mm, full-depth 20° teeth

> What are the tooth dimensions of a module 1 rack?

- 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/gear-rack-m1-120-full-depth/ · JSON: https://xemstudio.com/api/geometry?object=gear-rack-m1-120-full-depth · Plain text: https://xemstudio.com/objects/gear-rack-m1-120-full-depth/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/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 120.0 | 11.0 | 8.0 |

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

## Notes

- Module 1 basic rack (ISO 53): straight 20° flanks, pitch π = 3.1416 mm, addendum 1 mm above the pitch line, dedendum 1.25 mm below it, tooth thickness π/2 on the pitch line; 120 × 8 mm, body to 10 mm below the pitch line, three Ø3.4 (M3 clearance) holes across it.
- A module 1 pinion of N teeth sits with its axis N/2 mm above the pitch line and moves the rack πN mm per turn.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| module | 1 |
| pressure angle | 20° |
| pitch | 3.1416 mm |
| addendum / dedendum | 1 / 1.25 mm |
| length × width | 120 × 8 mm |
| pitch line to back | 10 mm |
| holes | 3 × Ø3.4 at x = −45, 0, 45 |

## 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. 113: figure, his text and an animation](https://507movements.com/mm_113.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/rack-and-pinion-mechanism/) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/gear-rack-m1-120-full-depth/index.json

- gear-rack-m1-120: [STEP](https://xemstudio.com/files/hardware/gear-rack-m1-120-full-depth/gear-rack-m1-120.step) · [STL](https://xemstudio.com/files/hardware/gear-rack-m1-120-full-depth/gear-rack-m1-120.stl) — rack, pitch line y = 0, a tooth centred at x = 0, z 0..8

## Questions

**What are the tooth dimensions of a module 1 rack?**

Module 1 basic rack (ISO 53): straight 20° flanks, pitch π = 3.1416 mm, addendum 1 mm above the pitch line, dedendum 1.25 mm below it, tooth thickness π/2 on the pitch line; 120 × 8 mm, body to 10 mm below the pitch line, three Ø3.4 (M3 clearance) holes across it.

## Fits with

- [Rack and pinion, module 1 (20 T pinion, 120 mm rack)](https://xemstudio.com/objects/rack-and-pinion-mechanism/)
- [Pinion between two racks (opposite motion, pump drive)](https://xemstudio.com/objects/opposed-racks-and-pinion-mechanism/)