# 8520 (820) coreless motor: Ø8.5 × 20 mm, Ø1 shaft

> What are the dimensions of an 8520 coreless motor?

- Category: Electronics › Motors
- Kind: Hardware
- Basis: DFRobot FIT0796 and Makeblock 820 listings (they agree). Envelope only: the outside of the motor at its published sizes. The windings, magnets, brushes and bearings inside are not drawn.
- Page: https://xemstudio.com/objects/coreless-motor-8520/ · JSON: https://xemstudio.com/api/geometry?object=coreless-motor-8520 · Plain text: https://xemstudio.com/objects/coreless-motor-8520/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**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

- Envelope only: the outside of the motor at its published sizes. The windings, magnets, brushes and bearings inside are not drawn.
- The body is a plain Ø8.5 × 20 mm cylinder; the Ø1.0 shaft stands 5 mm out of the front end.
- 8520 and 820 are the same size: 8.5 mm diameter, 20 mm long.
- The leads leave the back end; they and any bearing boss are not drawn (not listed). It is held by its body in a Ø8.5 clip or socket.
- Coreless motors have no iron in the rotor, so they turn without cogging; on small, low-power Stirling models they are used as generators or tachometer pickups.

## 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 |
|---|---|---|---|---|
| shaft | Ø1.0 | propeller or pinion bore (pressed on) | press | coreless-8520* |
| body | Ø8.5 × 20 | clip or socket | socket | coreless-8520* |

## Sizes

| feature | mm | from |
|---|---|---|
| body | Ø8.5 × 20 | DFRobot FIT0796, Makeblock 820 |
| shaft | Ø1.0 × 5 | DFRobot FIT0796, Makeblock 820 |

## Where the files are

- DFRobot (FIT0796, as listed by Core Electronics): [Coreless micro motor 8.5 × 20 mm: Ø8.5 × 20, shaft Ø1 × 5](https://core-electronics.com.au/4pcs-coreless-micro-motor-8-5-20mm.html.plain.md) — web — listing (verify at link)
- Makeblock (as listed by Studica): [820 coreless motor: Ø8.5 × 20, output shaft Ø1.0 × 5](https://www.studica.com/makeblock-820-coreless-motor-pair) — web — listing (verify at link)

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/coreless-motor-8520/index.json

- coreless-8520: [STEP](https://xemstudio.com/files/hardware/coreless-motor-8520/coreless-8520.step) · [STL](https://xemstudio.com/files/hardware/coreless-motor-8520/coreless-8520.stl) — 8520 coreless envelope: Ø8.5 × 20 body, Ø1.0 shaft 5 long

## How it fits

### Alternatives
- [716 coreless motor: Ø7 × 16 mm, Ø0.8 shaft](https://xemstudio.com/objects/coreless-motor-716/): smaller Ø7 × 16, Ø0.8 shaft
- [130 size brushed DC motor: Ø20.1 / 15.1 × 25.0 mm, Ø2 shaft](https://xemstudio.com/objects/dc-motor-130-size/): iron-core can, Ø2 shaft

### Also needed
- [Through-hole LEDs: 3, 5, 8, 10 mm, flat-top, rectangular, RGB](https://xemstudio.com/objects/leds-tht/): an LED across the leads shows generator output

## Questions

**What size is an 8520 motor?**

Ø8.5 mm × 20 mm body with a Ø1.0 mm shaft 5 mm long.

**Is an 820 motor the same as an 8520?**

Yes: both are 8.5 mm × 20 mm with a 1 mm shaft.

## Fits with

- [716 coreless motor: Ø7 × 16 mm, Ø0.8 shaft](https://xemstudio.com/objects/coreless-motor-716/)
- [130 size brushed DC motor: Ø20.1 / 15.1 × 25.0 mm, Ø2 shaft](https://xemstudio.com/objects/dc-motor-130-size/)