# Hex nuts M8, M10, M12, 3/8 in and 1/2 in (flywheel weights)

> What are the dimensions of the hex nuts that fill the flywheel pockets?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: ISO 4032 (M8, M10, M12) and ASME B18.2.2 finished hex (3/8, 1/2 in) envelopes; bore at the thread major Ø
- Page: https://xemstudio.com/objects/hex-nut-weights/ · JSON: https://xemstudio.com/api/geometry?object=hex-nut-weights · Plain text: https://xemstudio.com/objects/hex-nut-weights/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

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

## Notes

- Hex nut envelopes: across flats × thickness, across corners, and a bore at the thread major Ø (thread not drawn).
- M8 13 × 6.8 (AC 15.01); M10 16 × 8.4 (18.48); M12 18 × 10.8 (20.78); 3/8 in 14.29 × 8.33 (16.50); 1/2 in 19.05 × 11.11 (22.00).
- Each sits in the matching flywheel pocket with one flat facing outward, flush with the rim face.

## Sizes

| file | thread | across flats | across corners | thickness | bore |
|---|---|---|---|---|---|
| nut-m8 | M8 | 13.0 | 15.01 | 6.8 | 8.0 |
| nut-m10 | M10 | 16.0 | 18.48 | 8.4 | 10.0 |
| nut-m12 | M12 | 18.0 | 20.78 | 10.8 | 12.0 |
| nut-3-8in | 3/8 in | 14.29 | 16.5 | 8.33 | 9.53 |
| nut-1-2in | 1/2 in | 19.05 | 22.0 | 11.11 | 12.7 |

## Where the files are

- ISO: [ISO 4032 Hexagon regular nuts (style 1)](https://www.iso.org/standard/72624.html) — standard — ISO (verify at link)
- ASME: [ASME B18.2.2 Nuts for general applications](https://www.asme.org/codes-standards/find-codes-standards/b18-2-2-nuts-for-general-applications-machine-screw-nuts-hex-square-hex-flange-coupling-nuts-(inch-series)) — standard — ASME (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (5 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/hex-nut-weights/index.json

- nut-m8: [STEP](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-m8.step) · [STL](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-m8.stl) — M8 hex nut, 13 across flats × 6.8: the flywheel weight
- nut-m10: [STEP](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-m10.step) · [STL](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-m10.stl) — M10 hex nut, 16 across flats × 8.4: the flywheel weight
- nut-m12: [STEP](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-m12.step) · [STL](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-m12.stl) — M12 hex nut, 18 across flats × 10.8: the flywheel weight
- nut-3-8in: [STEP](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-3-8in.step) · [STL](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-3-8in.stl) — 3/8 in hex nut, 14.29 across flats × 8.33: the flywheel weight
- nut-1-2in: [STEP](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-1-2in.step) · [STL](https://xemstudio.com/files/hardware/nut-weighted-flywheels/nut-1-2in.stl) — 1/2 in hex nut, 19.05 across flats × 11.11: the flywheel weight

## How it fits

### Goes in or on
- [Flywheels Ø100–Ø200 with hex-nut rim pockets](https://xemstudio.com/objects/nut-pocket-flywheels/): hex pocket at the across-flats

### Alternatives
- [Hex nuts, M2–M8 (ISO 4032)](https://xemstudio.com/objects/hex-nuts-metric/): M2–M8 nut range

## Questions

**What are M10 hex nut dimensions?**

16 across flats, 18.48 across corners, 8.4 thick (ISO 4032).

**What are 1/2 in hex nut dimensions?**

3/4 in (19.05) across flats, 7/16 in (11.11) thick (ASME B18.2.2 finished hex).

## Fits with

- [Flywheels Ø100–Ø200 with hex-nut rim pockets](https://xemstudio.com/objects/nut-pocket-flywheels/)
- [Hex nuts, M2–M8 (ISO 4032)](https://xemstudio.com/objects/hex-nuts-metric/)
- [Nyloc lock nuts, M2.5–M8 (DIN 985)](https://xemstudio.com/objects/nyloc-nuts-metric/)