# Lazy tongs (three-cell scissor linkage)

> How much do lazy tongs multiply motion?

- Category: Mechanisms › Linkages
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 144 (1868)
- Page: https://xemstudio.com/objects/lazy-tongs-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=lazy-tongs-mechanism · Plain text: https://xemstudio.com/objects/lazy-tongs-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

- Crossed bars pinned at their middles and ends: closing the handles a little extends the far end a lot. With n cells the end moves n times as far as the first cell's joint (3 here), and every joint stays on the centre line.
- Each bar is the 80 mm centre-hole link; length along the axis = 2·n·40·cos α (207.8 mm at α = 30° here).
- Brown's No. 144 (lazy tongs); the scissor lift and the extending mirror arm are the same linkage.
- Parts (each has its own page): centre-hole-link-80, dowel-pins-metric.
- Brown's movement No. 144 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| cells | 3 |
| bars | 6 × 80 mm centre-hole links |
| angle drawn | 30° to the axis |
| reach at 30° | 207.8 mm |

## 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. 144: figure, his text and an animation](https://507movements.com/mm_144.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/lazy-tongs-mechanism/index.json

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

## Questions

**How much do lazy tongs multiply motion?**

Crossed bars pinned at their middles and ends: closing the handles a little extends the far end a lot. With n cells the end moves n times as far as the first cell's joint (3 here), and every joint stays on the centre line.

## Fits with

- [Centre-hole link, 80 mm (three Ø3 holes: −40, 0, +40)](https://xemstudio.com/objects/centre-hole-link-80/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)