# Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23

> What size pin is a crank pin, wrist pin or link pivot on a small engine?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Solid Ø3 pins at the Ø3 pin holes of the crank discs, webs, clevises and pistons
- Page: https://xemstudio.com/objects/pins-3mm/ · JSON: https://xemstudio.com/api/geometry?object=pins-3mm · Plain text: https://xemstudio.com/objects/pins-3mm/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

- Solid Ø3 pins, 12, 16, 19, 20 and 23 long, 0.3 chamfers both ends.
- They sit fixed in the crank disc and web pin holes, the yoke and the clevis tines, and the con-rods turn on them; each fit is listed under Mating features.
- Ø3 × 16 is the wrist pin through the free-piston plug legs; Ø3 × 23 is the alpha V-twin crank pin (disc 6, two rods and two 1 mm spacers, then a full 5 mm collar) and the Ross yoke's rocking pin.

## 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 |
|---|---|---|---|---|
| shafts, rods, pins | Ø3 / Ø5 / Ø8 | the bores listed on each mating object | slide | all |

## Sizes

| file | Ø | length |
|---|---|---|
| pin-3x12 | 3 | 12 |
| pin-3x16 | 3 | 16 |
| pin-3x19 | 3 | 19 |
| pin-3x20 | 3 | 20 |
| pin-3x23 | 3 | 23 |

## Where the files are

- Long Earth Society: [Engine builds](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/pins-3mm/index.json

- pin-3x12: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x12.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x12.stl) — Ø3 × 12 pin: crank pin, wrist pin, link pivot
- pin-3x16: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x16.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x16.stl) — Ø3 × 16 pin: crank pin, wrist pin, link pivot
- pin-3x19: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x19.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x19.stl) — Ø3 × 19 pin: crank pin, wrist pin, link pivot
- pin-3x20: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x20.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x20.stl) — Ø3 × 20 pin: crank pin, wrist pin, link pivot
- pin-3x23: [STEP](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x23.step) · [STL](https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x23.stl) — Ø3 × 23 pin: crank pin, wrist pin, link pivot

## How it fits

### Goes in or on
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/): Ø3 pin hole at stroke / 2
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/): Ø3 hole across the 5 mm gap

### Connects to
- [Connecting rods 30 to 80 mm centres with 623 pockets](https://xemstudio.com/objects/connecting-rods-623/): 623 bore on the pin

### Alternatives
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/): ISO 2338 Ø3 dowel

## Questions

**What diameter crank pin fits a 623 bearing?**

Ø3, the 623 bore. The pins are 12, 16, 19, 20 and 23 long.

**Which pin is the wrist pin?**

Ø3 × 16 through the piston plug legs.

## Fits with

- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)
- [Connecting rods 30 to 80 mm centres with 623 pockets](https://xemstudio.com/objects/connecting-rods-623/)
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/)
- [Clevis pins ISO 2341 B, Ø3 to Ø8](https://xemstudio.com/objects/clevis-pins/)