# Hex nuts, M2–M8 (ISO 4032)

> What size pocket does an M3 nut need in a 3D print?

- Category: Hardware › Fasteners
- Kind: Hardware
- Basis: ISO 4032 (DIN 934 matches for M2–M8; they differ at M10 and up)
- Page: https://xemstudio.com/objects/hex-nuts-metric/ · JSON: https://xemstudio.com/api/geometry?object=hex-nuts-metric · Plain text: https://xemstudio.com/objects/hex-nuts-metric/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- Width across flats (AF) and thickness per size below. A printed nut trap: AF + 0.2–0.3 mm, thickness + 0.3 mm, and the corner-to-corner dimension is AF × 1.155.
- M3: 5.5 AF, 2.4 thick → print a 5.8 mm hex, 2.8 deep.

## Sizes

| thread | width_af_mm | corner_mm | thickness_mm |
|---|---|---|---|
| M2 | 4 | 4.6 | 1.6 |
| M2.5 | 5 | 5.8 | 2 |
| M3 | 5.5 | 6.4 | 2.4 |
| M4 | 7 | 8.1 | 3.2 |
| M5 | 8 | 9.2 | 4.7 |
| M6 | 10 | 11.5 | 5.2 |
| M8 | 13 | 15 | 6.8 |

## Where the files are

- McMaster-Carr: [Hex nuts (free STEP/IGES/STL per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/nuts/hex-nuts/) — STEP, IGES, STL, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)
- Wikipedia: [Nut (hardware)](https://en.wikipedia.org/wiki/Nut_(hardware)) — web — CC BY-SA 4.0 (text)

## Free STEP/STL (7 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/hex-nuts-metric/index.json

- nut-m2: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m2.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m2.stl) — ISO 4032 M2
- nut-m2.5: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m2.5.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m2.5.stl) — ISO 4032 M2.5
- nut-m3: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m3.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m3.stl) — ISO 4032 M3
- nut-m4: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m4.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m4.stl) — ISO 4032 M4
- nut-m5: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m5.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m5.stl) — ISO 4032 M5
- nut-m6: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m6.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m6.stl) — ISO 4032 M6
- nut-m8: [STEP](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m8.step) · [STL](https://xemstudio.com/files/hardware/hex-nuts-metric/nut-m8.stl) — ISO 4032 M8

## Questions

**What size is an M3 nut?**

5.5 mm across flats, 6.4 mm across corners, 2.4 mm thick (ISO 4032). Print a nut trap 5.8 mm across flats and 2.8 mm deep.

**What size is an M4 nut and M5 nut?**

M4: 7 mm across flats, 3.2 mm thick. M5: 8 mm across flats, 4.7 mm thick. Across corners = AF × 1.155.

**How to model a captive nut pocket in a 3D print?**

Hex pocket at AF + 0.2–0.3 mm, depth = nut thickness + 0.3 mm, slot it in from the side so the nut can't spin, and keep at least 1.5 mm of wall around the corners.

## Fits with

- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/)
- [Flat washers, M2–M8 (ISO 7089)](https://xemstudio.com/objects/flat-washers-metric/)
- [Threaded standoffs, M2.5 and M3 (hex and round)](https://xemstudio.com/objects/threaded-standoffs-metric/)