# CD and HDD-platter flywheel hubs: Ø15 and Ø25 spigots for Ø3 / 5 / 8 shafts

> What are the dimensions of a hub that mounts a CD or hard-drive platter on a shaft?

- Category: Stirling engines › Can & LTD engines
- Kind: Standard part
- Basis: Spigot at the disc's centre hole (CD Ø15, 3.5 in HDD platter Ø25); bore at the shaft; M3 tap drill Ø2.5 for the set screw
- Page: https://xemstudio.com/objects/flywheel-disc-hub/ · JSON: https://xemstudio.com/api/geometry?object=flywheel-disc-hub · Plain text: https://xemstudio.com/objects/flywheel-disc-hub/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 hub that carries a CD/DVD or a 3.5 in hard-drive platter as a flywheel. The spigot is the disc's centre hole exactly: Ø15 for a CD, Ø25 for a platter, 1.3 tall.
- As drawn, the spigot sits between a Ø(spigot + 8) × 2 collar below and the Ø(spigot + 8) hub body above (Ø23 for CD hubs, Ø33 for platter hubs), 12 mm overall.
- Bores: Ø3, Ø5 or Ø8 (fit: slide) for the shaft, with a Ø2.5 radial hole (M3 tap size) 6 mm above the lower collar for an M3 set screw.

## 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 |
|---|---|---|---|---|
| CD hub spigot | Ø15 | CD / DVD centre hole | press | hub-cd-* |
| platter hub spigot | Ø25 | 3.5 in HDD platter hole | press | hub-platter-* |
| hub bore | Ø3 / Ø5 / Ø8 | shaft (M3 set screw) | slide | hub-* |
| hub set-screw hole | Ø2.5 | M3 tap drill | designed | hub-* |

## Sizes

| file | disc | spigot | bore | outside | height |
|---|---|---|---|---|---|
| hub-cd-15-to-3 | CD / DVD | 15 | 3 | 23 | 12 |
| hub-cd-15-to-5 | CD / DVD | 15 | 5 | 23 | 12 |
| hub-cd-15-to-8 | CD / DVD | 15 | 8 | 23 | 12 |
| hub-platter-25-to-5 | 3.5 in HDD platter | 25 | 5 | 33 | 12 |
| hub-platter-25-to-8 | 3.5 in HDD platter | 25 | 8 | 33 | 12 |

## Where the files are

- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Can engine build](https://longearthsociety.com/engineering/) — video, web — LES site
- Long Earth Society: [Engine builds (videos and write-ups)](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/flywheel-disc-hub/index.json

- hub-cd-15-to-3: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-cd-15-to-3.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-cd-15-to-3.stl) — CD / DVD hub: Ø23 × 10 boss with a Ø3 shaft bore and M3 set-screw hole (Ø2.5), Ø15 × 1.2 spigot that takes the disc
- hub-cd-15-to-5: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-cd-15-to-5.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-cd-15-to-5.stl) — CD / DVD hub: Ø23 × 10 boss with a Ø5 shaft bore and M3 set-screw hole (Ø2.5), Ø15 × 1.2 spigot that takes the disc
- hub-cd-15-to-8: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-cd-15-to-8.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-cd-15-to-8.stl) — CD / DVD hub: Ø23 × 10 boss with a Ø8 shaft bore and M3 set-screw hole (Ø2.5), Ø15 × 1.2 spigot that takes the disc
- hub-platter-25-to-8: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-platter-25-to-8.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-platter-25-to-8.stl) — 3.5 in HDD platter hub: Ø33 × 10 boss with a Ø8 shaft bore and M3 set-screw hole (Ø2.5), Ø25 × 1.27 spigot that takes the platter
- hub-platter-25-to-5: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-platter-25-to-5.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/hub-platter-25-to-5.stl) — 3.5 in HDD platter hub: Ø33 × 10 boss with a Ø5 shaft bore and M3 set-screw hole (Ø2.5), Ø25 × 1.27 spigot that takes the platter

## How it fits

### Goes in or on
- [CD / DVD disc Ø120 × 1.2 mm with Ø15 hole (and mini CD Ø80)](https://xemstudio.com/objects/cd-dvd-discs/): Ø15 / Ø25 spigot in the disc's centre hole

### Connects to
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/): Ø3 / Ø5 / Ø8 shaft in the bore
- [Craft sticks 114 × 10 × 2 mm and jumbo 150 × 18 × 2 mm](https://xemstudio.com/objects/craft-sticks/): Ø3 skewer in the Ø3 bore

### Alternatives
- [Flywheels Ø100–Ø200 with hex-nut rim pockets](https://xemstudio.com/objects/nut-pocket-flywheels/): a nut-weighted flywheel instead of a disc

### Also needed
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/): M3 set screw in the Ø2.5 hole

## Questions

**What is the hole in a CD?**

Ø15; the CD hubs here have a Ø15 spigot 1.3 tall to match it.

**Which hub goes on a bamboo skewer?**

Hub-cd-15-to-3: Ø3 bore, Ø15 spigot, M3 set screw.

## Fits with

- [CD / DVD disc Ø120 × 1.2 mm with Ø15 hole (and mini CD Ø80)](https://xemstudio.com/objects/cd-dvd-discs/)
- [Crank stand for a 623 bearing, 40 / 60 / 80 mm](https://xemstudio.com/objects/can-engine-crank-stand/)
- [Flywheels Ø100–Ø200 with hex-nut rim pockets](https://xemstudio.com/objects/nut-pocket-flywheels/)
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/)
- [Build list: Soda-can gamma](https://xemstudio.com/objects/list-can-engine/)