# Helical gear, normal module 1.5, 30 teeth, helix 20° left hand, face 12, Ø8 bore

> What are the dimensions of a 30-tooth, 20° helical gear?

- 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/helical-gear-mn1-5-30t-beta20-lh-bore8/ · JSON: https://xemstudio.com/api/geometry?object=helical-gear-mn1-5-30t-beta20-lh-bore8 · Plain text: https://xemstudio.com/objects/helical-gear-mn1-5-30t-beta20-lh-bore8/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 |
|---|---|---|
| 50.89 | 50.89 | 12.0 |

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

## Notes

- Normal module 1.5, helix angle 20°: transverse module 1.6, transverse pressure angle 21.17°, pitch Ø47.89, tip Ø50.89, root Ø44.14; addendum 1.5, dedendum 1.88 (normal-module depths).
- The transverse involute is twisted 10.45° over the 12 mm face (lead π·d / tan β = 413.34 mm). Meshes with a 20-tooth gear of the opposite hand on a parallel shaft.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| normal module | 1.5 |
| teeth | 30 |
| helix angle | 20° LH |
| transverse module | 1.6 |
| pitch Ø | 47.89 mm |
| tip Ø | 50.89 mm |
| face | 12 mm |
| bore | Ø8 |

## 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. 40: figure, his text and an animation](https://507movements.com/mm_040.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/helical-gears-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/helical-gear-mn1-5-30t-beta20-lh-bore8/index.json · license: https://xemstudio.com/files/hardware/helical-gear-mn1-5-30t-beta20-lh-bore8/LICENSE.md

- helical-gear-mn1-5-30t-beta20-lh-bore8: [STEP](https://xemstudio.com/files/hardware/helical-gear-mn1-5-30t-beta20-lh-bore8/helical-gear-mn1-5-30t-beta20-lh-bore8.step) · [STL](https://xemstudio.com/files/hardware/helical-gear-mn1-5-30t-beta20-lh-bore8/helical-gear-mn1-5-30t-beta20-lh-bore8.stl) — gear, axis Z, z 0..12, a tooth on +X at z = 0

## Questions

**What are the dimensions of a 30-tooth, 20° helical gear?**

Normal module 1.5, helix angle 20°: transverse module 1.6, transverse pressure angle 21.17°, pitch Ø47.89, tip Ø50.89, root Ø44.14; addendum 1.5, dedendum 1.88 (normal-module depths).

## Fits with

- [Helical (oblique-toothed) gears on parallel shafts, 20 : 30, helix 20°](https://xemstudio.com/objects/helical-gears-mechanism/)