# Gear racks: module 1 (100 mm) and module 2 (150 mm)

> Where can I get a 3D printable gear rack?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Involute rack, 20° pressure angle, module 1 and 2, matching the spur gears here
- Page: https://xemstudio.com/objects/gear-racks/ · JSON: https://xemstudio.com/api/geometry?object=gear-racks · Plain text: https://xemstudio.com/objects/gear-racks/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- Straight toothed bars that mesh with the module 1 and module 2 spur gears to turn rotation into straight-line travel.
- One turn of a z-tooth pinion moves the rack π × module × z: 62.8 mm for a 20-tooth module 1 gear.
- Module 1: 100 mm long, 8 × 8, three Ø3.4 mounting holes. Module 2: 150 mm long, 12 high × 10 wide.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| mounting holes | Ø3.4 | M3 screw clearance | designed | rack-m* |

## Sizes

| module | length | section | travel per turn, 20 T pinion |
|---|---|---|---|
| 1 | 100 mm | 8 × 8 | 62.8 mm |
| 2 | 150 mm | 12 × 10 | 125.7 mm |

## Where the files are

- Wikipedia: [Rack and pinion](https://en.wikipedia.org/wiki/Rack_and_pinion) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine and rig builds on extrusion frames](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/gear-racks/index.json

- rack-m1-100: [STEP](https://xemstudio.com/files/hardware/gear-racks/rack-m1-100.step) · [STL](https://xemstudio.com/files/hardware/gear-racks/rack-m1-100.stl) — rack, module 1, 100 mm, 8 high × 8 wide, three Ø3.4 mounting holes; meshes with the module 1 spur gears
- rack-m2-150: [STEP](https://xemstudio.com/files/hardware/gear-racks/rack-m2-150.step) · [STL](https://xemstudio.com/files/hardware/gear-racks/rack-m2-150.stl) — rack, module 2, 150 mm, 12 high × 10 wide; meshes with the module 2 spur gears

## How it fits

### Goes in or on
- [Aluminium T-slot extrusion: 2020, 2040, 2060, 2080, V-slot, 3030, 3060, 4040, 4080, 1010, 1515](https://xemstudio.com/objects/t-slot-extrusions/): rack bolted along a frame

### Connects to
- [Spur gears, involute 20°: module 0.5, 1 and 2, 12–60 teeth](https://xemstudio.com/objects/spur-gears-involute/): module 1 / 2 pinion

### Alternatives
- [T8 lead screw and brass nut (Tr8×8, 2 mm pitch 4-start)](https://xemstudio.com/objects/lead-screw-t8/): screw drive instead of rack

## Questions

**Which gear meshes with these racks?**

Any 20° module 1 or module 2 spur gear; the spur gear page has matching ones.

**How far does the rack move per turn?**

Π × module × teeth: 62.8 mm for a 20-tooth module 1 pinion.

## Fits with

- [Spur gears, involute 20°: module 0.5, 1 and 2, 12–60 teeth](https://xemstudio.com/objects/spur-gears-involute/)
- [Aluminium T-slot extrusion: 2020, 2040, 2060, 2080, V-slot, 3030, 3060, 4040, 4080, 1010, 1515](https://xemstudio.com/objects/t-slot-extrusions/)
- [MGN9 / MGN12 / MGN15 miniature linear rails and carriages](https://xemstudio.com/objects/mgn-linear-rails/)