# Gear rack

Straight-tooth rack. Length along X, centred on the origin; width along Y; base on the XY plane, teeth up along +Z.

## Geometry

As many whole teeth as fit the length, centred, at pitch π m, with the root level running on to both ends. Tooth
thickness π m / 2 on the pitch line, 20° flanks, addendum 1.0 m, dedendum 1.25 m.

## Source

- **Teeth:** ISO 53:1998, standard basic rack profile.
- **Section:** KHK Gears, catalogue 2025, Racks, SR steel racks table,
  <https://khkgears.us/media/yzroimcg/catalog-2025-racks.pdf>:

| Module | Face width B | Height H | Height to pitch line H0 |
|---|---|---|---|
| 0.5 | 5 | 12 | 11.5 |
| 0.8 | 8 | 12.3 | 11.5 |
| 1 | 10 | 12 | 11 |
| 1.5 | 15 | 20 | 18.5 |
| 2 | 20 | 25 | 23 |

Module 1.25 isn't in that table, so it isn't offered. A rack is limited to 260 teeth: longer ones take more than a build's time limit. The catalogue's preset widths differ for some modules: this part
uses the KHK section. Maker names identify the source; this part isn't made by or affiliated with KHK.

Preset lengths: step.parts catalogue metadata (MIT, `library/NOTICE.md`).