Crank discs for a Ø5 shaft, 10 to 30 mm stroke — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/crank-discs-5mm-bore/  (CC BY 4.0)
Basis: Disc 6 thick, Ø5 bore, Ø3 pin hole at stroke / 2, M3 grub; disc Ø = max(30, stroke + 12)
Catalog version: 2026-10-20

Sizes: see table below
- A 6 mm disc with a Ø5 bore and a Ø3 crank-pin hole at half the stroke from the axis: 5.0, 7.5, 10.0, 12.5, 15.0 mm for 10–30 mm stroke.
- Disc Ø grows with the stroke: Ø30 (10 and 15), Ø32 (20), Ø37 (25), Ø42 (30).
- A radial Ø2.5 hole (M3 tap drill) at mid-thickness locks the disc to the shaft's D-flat.
- The crank pin is fixed in the disc and the con-rod's 623 turns on it; fits are under Mating features.

file  stroke  pin offset  disc Ø × t  bore
crank-disc-stroke10  10  5.0  30 × 6  5
crank-disc-stroke15  15  7.5  30 × 6  5
crank-disc-stroke20  20  10.0  32 × 6  5
crank-disc-stroke25  25  12.5  37 × 6  5
crank-disc-stroke30  30  15.0  42 × 6  5

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Crank (mechanism) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Crank_(mechanism)
- Wikipedia: Flywheel — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Flywheel
- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine
- Long Earth Society: Engine builds that use these parts (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 5 parts): https://xemstudio.com/files/hardware/crank-discs-5mm-bore/index.json
API: https://xemstudio.com/api/geometry?object=crank-discs-5mm-bore