Hard-drive platters: 3.5 in Ø95 × 1.27 mm (Ø25 hole), 2.5 in Ø65 × 0.8 mm (Ø20 hole) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/hdd-platters/  (CC BY 4.0)
Basis: 3.5 in (95 mm) and 2.5 in (65 mm) hard-drive form-factor platters
Catalog version: 2026-10-20

Sizes: see table below
- 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).

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

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Compact disc — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Compact_disc
- Wikipedia: Hard disk drive platter — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Hard_disk_drive_platter
- Long Earth Society: Engine builds (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 2 parts): https://xemstudio.com/files/hardware/hdd-platters/index.json
API: https://xemstudio.com/api/geometry?object=hdd-platters