# Butterfly key (bow-tie, dutchman)

> What size is a butterfly key?

- Category: Joinery › Keys & inlays
- Kind: Hardware
- Basis: Xem Studio design — geometry computed in the generator from traditional proportions
- Page: https://xemstudio.com/objects/butterfly-key-joint/ · JSON: https://xemstudio.com/api/geometry?object=butterfly-key-joint · Plain text: https://xemstudio.com/objects/butterfly-key-joint/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 |
|---|---|---|
| 80.0 | 80.0 | 20.0 |

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

## Notes

- Woodworking joint drawn for 3D printing: the parts lock together by shape, so a print can be joined without glue or screws. Drawn at true size with the parts line to line (zero gap) in their assembled position — add your printer's fit allowance to the mating faces (your AI or slicer can do this).
- A bow-tie shaped key let into the surface across a joint or a crack.

## Sizes

| dimension | value |
|---|---|
| stock | 20 mm boards edge to edge |
| parts | board a, board b, key |
| key | 40 long, 16 at the ends, 8 at the waist, 8 mm deep |
| assembles | boards together, key pressed in from above |
| holds | the two boards (or a crack) from pulling apart |

## Where the files are

- Xem Studio: [Joinery design (geometry computed in the generator from traditional proportions)](https://xemstudio.com/) — web — Xem Studio design

## Free STEP/STL (4 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/butterfly-key-joint/index.json · license: https://xemstudio.com/files/hardware/butterfly-key-joint/LICENSE.md

- butterfly-key-joint-board-a: [STEP](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-board-a.step) · [STL](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-board-a.stl) — Board with half the bow-tie socket
- butterfly-key-joint-board-b: [STEP](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-board-b.step) · [STL](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-board-b.stl) — Board with the other half
- butterfly-key-joint-key: [STEP](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-key.step) · [STL](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-key.stl) — Bow-tie key, 8 mm deep
- butterfly-key-joint-assembled: [STEP](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-assembled.step) · [STL](https://xemstudio.com/files/hardware/butterfly-key-joint/butterfly-key-joint-assembled.stl) — All parts in their assembled position (each part its own solid)

## Questions

**How deep should a butterfly key be?**

About a third to half the board: 8 mm in 20 mm here.

## Fits with

- [Tongue and groove joint](https://xemstudio.com/objects/tongue-and-groove-joint/)
- [Splined mitre joint (hidden spline)](https://xemstudio.com/objects/splined-mitre-joint/)