# Hard-drive platters: 3.5 in Ø95 × 1.27 mm (Ø25 hole), 2.5 in Ø65 × 0.8 mm (Ø20 hole)

> What are hard drive platter dimensions?

- Category: Hardware › Found & household materials
- Kind: Standard part
- Basis: 3.5 in (95 mm) and 2.5 in (65 mm) hard-drive form-factor platters
- Page: https://xemstudio.com/objects/hdd-platters/ · JSON: https://xemstudio.com/api/geometry?object=hdd-platters · Plain text: https://xemstudio.com/objects/hdd-platters/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

- A 3.5 in drive platter is Ø95 × 1.27 mm (some 0.8–1.0) with a Ø25 mm centre hole, about 30 g.
- A 2.5 in drive platter is Ø65 × 0.8 mm with a Ø20 mm centre hole, about 7 g.
- Platters are flat and balanced; three 3.5 in platters stacked are about 90 g at Ø95.
- The hubs in the can-engine kit take a 3.5 in platter's Ø25 hole onto a 5 or 8 mm shaft (spigot drawn at Ø25.0).

## Sizes

| platter | dia_mm | thickness_mm | hole_mm | mass_g |
|---|---|---|---|---|
| 3.5 in | 95 | 1.27 | 25 | 30 |
| 2.5 in | 65 | 0.8 | 20 | 7 |

## Where the files are

- Wikipedia: [Compact disc](https://en.wikipedia.org/wiki/Compact_disc) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Hard disk drive platter](https://en.wikipedia.org/wiki/Hard_disk_drive_platter) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine builds (videos and write-ups)](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/hdd-platters/index.json

- hdd-platter-3-5in: [STEP](https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-3-5in.step) · [STL](https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-3-5in.stl) — 3.5 in hard-drive platter: Ø95 × 1.27, Ø25 hole (aluminium or glass)
- hdd-platter-2-5in: [STEP](https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-2-5in.step) · [STL](https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-2-5in.stl) — 2.5 in platter: Ø65 × 0.8, Ø20 hole

## How it fits

### Goes in or on
- [Can-engine cap for 53.3, 58, 66 and 76.2 mm cans](https://xemstudio.com/objects/can-engine-cap/): Ø25 hole on the hub's Ø25.0 spigot

### Alternatives
- [CD / DVD disc Ø120 × 1.2 mm with Ø15 hole (and mini CD Ø80)](https://xemstudio.com/objects/cd-dvd-discs/): lighter Ø120 disc
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/): a drawn flywheel

## Questions

**What are 3.5 inch hard drive platter dimensions?**

Ø95 mm, Ø25 mm hole, about 1.27 mm thick (0.8–1.0 in some drives).

**What is a 2.5 inch platter's size?**

Ø65 × 0.8 mm with a Ø20 mm hole.

**Are all 3.5 in platters the same thickness?**

No; 1.27 mm is common, some drives use 0.8–1.0 mm platters with the same Ø95 / Ø25 size.

## Fits with

- [CD / DVD disc Ø120 × 1.2 mm with Ø15 hole (and mini CD Ø80)](https://xemstudio.com/objects/cd-dvd-discs/)
- [Can-engine cap for 53.3, 58, 66 and 76.2 mm cans](https://xemstudio.com/objects/can-engine-cap/)
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)
- [2.5-inch drive (SATA SSD / HDD)](https://xemstudio.com/objects/2-5-inch-drive/)