# Screw jack, Tr16×4 (4 mm lift per turn)

> How much force does a screw jack give?

- Category: Mechanisms › Screws
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 389 (1868)
- Page: https://xemstudio.com/objects/screw-jack-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=screw-jack-mechanism · Plain text: https://xemstudio.com/objects/screw-jack-mechanism/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/)

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

## Notes

- Turning the screw in its threaded body lifts it one pitch per turn (4 mm). Ideal force gain = 2π × lever radius / pitch: 2π × 40 / 4 ≈ 63 with the 80 mm tommy bar; friction in the 30° thread takes about two-thirds of that and keeps the load from running back.
- Basic-profile Tr16×4 trapezoidal thread on screw and body, drawn engaged with no allowance.
- Brown's No. 389 (lifting jack).
- Parts (each has its own page): screw-jack-screw-tr16x4, screw-jack-body-tr16x4, tommy-bar-6x80.
- Brown's movement No. 389 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| thread | Tr16×4 |
| lift per turn | 4 mm |
| lever radius | 40 mm |
| ideal gain | ≈ 63 |

## 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. 389: figure, his text and an animation](https://507movements.com/mm_389.html) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/screw-jack-mechanism/index.json

- screw-jack-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/screw-jack-mechanism/screw-jack-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/screw-jack-mechanism/screw-jack-mechanism-assembly.stl) — Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)

## Questions

**How much force does a screw jack give?**

Turning the screw in its threaded body lifts it one pitch per turn (4 mm). Ideal force gain = 2π × lever radius / pitch: 2π × 40 / 4 ≈ 63 with the 80 mm tommy bar; friction in the 30° thread takes about two-thirds of that and keeps the load from running back.

## Fits with

- [Screw-jack screw Tr16×4, 90 mm thread, Ø28 head with tommy-bar holes](https://xemstudio.com/objects/screw-jack-screw-tr16x4/)
- [Screw-jack body with Tr16×4 internal thread, Ø60 base, 50 high](https://xemstudio.com/objects/screw-jack-body-tr16x4/)
- [Tommy bar Ø6 × 80](https://xemstudio.com/objects/tommy-bar-6x80/)