# Splined mitre joint (hidden spline)

> How big is the spline in a mitre joint?

- Category: Joinery › Mitre joints
- Kind: Hardware
- Basis: Xem Studio design — geometry computed in the generator from traditional proportions
- Page: https://xemstudio.com/objects/splined-mitre-joint/ · JSON: https://xemstudio.com/api/geometry?object=splined-mitre-joint · Plain text: https://xemstudio.com/objects/splined-mitre-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 thin spline across the mitre faces lines the corner up and stops it slipping.

## Sizes

| dimension | value |
|---|---|
| stock | 20 × 20 mm square |
| parts | part a, part b, spline |
| mitre | 45° |
| spline | 3 mm thick, 18 mm along the mitre, 10 mm across it, hidden inside |
| assembles | spline into one slot, close the mitre |
| holds | keeps the mitre aligned and adds strength |

## 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/splined-mitre-joint/index.json · license: https://xemstudio.com/files/hardware/splined-mitre-joint/LICENSE.md

- splined-mitre-joint-part-a: [STEP](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-part-a.step) · [STL](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-part-a.stl) — Mitred member A with a spline slot
- splined-mitre-joint-part-b: [STEP](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-part-b.step) · [STL](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-part-b.stl) — Mitred member B with a spline slot
- splined-mitre-joint-spline: [STEP](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-spline.step) · [STL](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-spline.stl) — Spline 18 × 10 × 3 mm
- splined-mitre-joint-assembled: [STEP](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-assembled.step) · [STL](https://xemstudio.com/files/hardware/splined-mitre-joint/splined-mitre-joint-assembled.stl) — All parts in their assembled position (each part its own solid)

## Questions

**How thick is a mitre spline?**

About 1/6 of the stock: 3 mm in 20 mm here.

## Fits with

- [Keyed mitre joint (feather keys)](https://xemstudio.com/objects/keyed-mitre-joint/)
- [Butterfly key (bow-tie, dutchman)](https://xemstudio.com/objects/butterfly-key-joint/)