# Face spiral (scroll) disc, pitch 3.14 (module 1), r 20 → 46.39, Ø100 × 6

> What is a face spiral disc?

- Category: Mechanisms › Screws & feeds
- Kind: Modern device
- Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
- Page: https://xemstudio.com/objects/face-spiral-disc-m1-r20-8-4turns-d100/ · JSON: https://xemstudio.com/api/geometry?object=face-spiral-disc-m1-r20-8-4turns-d100 · Plain text: https://xemstudio.com/objects/face-spiral-disc-m1-r20-8-4turns-d100/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 |
|---|---|---|
| 100.0 | 100.0 | 8.25 |

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

## Notes

- A Ø100 × 6 disc with one raised Archimedean spiral rib on its face: radial pitch p = π m = 3.14 mm, from radius 20 to 46.39 (8.4 turns), Ø8 bore. The rib's radial section is the basic rack of module 1 (20° flanks, πm/2 thick at its pitch height 1.25 mm above the face, top at 2.25 mm): seen by a toothed part standing over the face, the rib is a rack that advances p per turn of the disc — a worm unrolled onto a face.
- Swept along the spiral with the profile kept upright and normal to the path; the bottom of the rib runs 0.5 mm into the disc so it is one solid.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| pitch p | 3.14 mm (module 1) |
| spiral | r 20 → 46.39, 8.4 turns |
| rib height | 2.25 mm above the face |
| disc | Ø100 × 6 |
| 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. 99: figure, his text and an animation](https://507movements.com/mm_099.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/face-spiral-rack-feed-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/face-spiral-disc-m1-r20-8-4turns-d100/index.json · license: https://xemstudio.com/files/hardware/face-spiral-disc-m1-r20-8-4turns-d100/LICENSE.md

- face-spiral-disc-m1-r20-8-4turns-d100: [STEP](https://xemstudio.com/files/hardware/face-spiral-disc-m1-r20-8-4turns-d100/face-spiral-disc-m1-r20-8-4turns-d100.step) · [STL](https://xemstudio.com/files/hardware/face-spiral-disc-m1-r20-8-4turns-d100/face-spiral-disc-m1-r20-8-4turns-d100.stl) — disc, axis Z, face at z = 0, rib up to z = 2.25

## Questions

**What is a face spiral disc?**

A Ø100 × 6 disc with one raised Archimedean spiral rib on its face: radial pitch p = π m = 3.14 mm, from radius 20 to 46.39 (8.4 turns), Ø8 bore. The rib's radial section is the basic rack of module 1 (20° flanks, πm/2 thick at its pitch height 1.25 mm above the face, top at 2.25 mm): seen by a toothed part standing over the face, the rib is a rack that advances p per turn of the disc — a worm unrolled onto a face.

## Fits with

- [Face spiral on a disc as a drill feed: scroll driving a rack](https://xemstudio.com/objects/face-spiral-rack-feed-mechanism/)