# Shaft adapter Ø5 to Ø8 × 20

> How does an 8 mm bore flywheel go on a 5 mm crankshaft?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Sleeve with a Ø5 bore and Ø8 OD, two M3 radial holes
- Page: https://xemstudio.com/objects/shaft-adapter-5-to-8mm/ · JSON: https://xemstudio.com/api/geometry?object=shaft-adapter-5-to-8mm · Plain text: https://xemstudio.com/objects/shaft-adapter-5-to-8mm/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- A sleeve Ø8 OD × Ø5 bore × 20 long.
- Two Ø2.5 radial holes (M3 tap drill) through both walls, 5 mm from each end: one grub bears on the Ø5 shaft's flat, the other lines up under the flywheel's set screw.
- It puts any Ø8-bore hub (the Ø80–Ø150 spoked flywheels) on a Ø5 crankshaft.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| shaft-adapter bore | Ø5 | Ø5 crankshaft | slide | shaft-adapter-* |
| shaft-adapter OD | Ø8 | Ø8 flywheel hub | slide | shaft-adapter-* |
| shaft-adapter grub holes | Ø2.5 | M3 tap drill | designed | shaft-adapter-* |

## Sizes

| feature | value_mm |
|---|---|
| OD | 8 |
| bore | 5 |
| length | 20 |
| grub holes | 2 × Ø2.5 at 5 and 15 |

## Where the files are

- Long Earth Society: [Tri-clamp Stirling engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/shaft-adapter-5-to-8mm/index.json

- shaft-adapter-5-to-8: [STEP](https://xemstudio.com/files/hardware/stirling-linkage-fittings/shaft-adapter-5-to-8.step) · [STL](https://xemstudio.com/files/hardware/stirling-linkage-fittings/shaft-adapter-5-to-8.stl) — Ø5 → Ø8 shaft adapter × 20 with two M3 grubs: puts a Ø8-bore flywheel (Ø80–150) on a Ø5 crankshaft

## How it fits

### Goes in or on
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/): Ø5 bore on the D-flat shaft

### Connects to
- [Spoked flywheels Ø50 to Ø150 × 10](https://xemstudio.com/objects/spoked-flywheels/): Ø8 OD in the flywheel's Ø8 bore

### Also needed
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/): two M3 grubs

## Questions

**The flywheel has an 8 mm bore and the crankshaft is 5 mm. What goes between?**

This adapter: Ø5 bore, Ø8 OD, 20 long, two M3 grub holes.

**How long is the shaft adapter?**

20 mm, with grub holes 5 mm in from each end.

## Fits with

- [Spoked flywheels Ø50 to Ø150 × 10](https://xemstudio.com/objects/spoked-flywheels/)
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/)
- [Flexible shaft couplers, 5–10 mm bores](https://xemstudio.com/objects/shaft-couplers/)
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/)