# NEMA 8 stepper motor: 20.2 mm face, 16 mm hole pattern

> What are the NEMA 8 stepper motor dimensions?

- Category: Electronics › Motors
- Kind: Hardware
- Basis: NEMA ICS 16 frame size 8 (face and mounting-hole pattern); pilot boss and shaft as commonly supplied; body length varies with torque. Envelope only: the outside of the motor. The windings, rotor and bearings inside are not drawn.
- Page: https://xemstudio.com/objects/nema-8-stepper/ · JSON: https://xemstudio.com/api/geometry?object=nema-8-stepper · Plain text: https://xemstudio.com/objects/nema-8-stepper/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. The windings, rotor and bearings inside are not drawn.
- NEMA 8 is a 0.8 in face: 20.2 mm square, with chamfered corners. The face and hole pattern are the standard; the body length is the maker's.
- Four M2 tapped holes on a 16 mm square, drawn as plain bores at the thread's major diameter (Ø2) 8 mm deep.
- Pilot boss Ø15 × 1.5; shaft Ø4 × 10 from the boss.
- Files: 30, 38 mm bodies. Leads and connector are not drawn.
- In DIY Stirling builds, a stepper turned by the engine is used as a two-phase generator; each coil pair gives AC that is rectified for a load.

## 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 |
|---|---|---|---|---|
| pilot boss | Ø15 / 22 / 22 / 38.1 / 73 | mount pilot bore | slide | nema* |
| shaft | Ø4 / 5 / 5 / 6.35 / 14 | coupler or pulley bore | slide | nema* |
| mount holes | M2 / M2.5 / M3 tapped, Ø5.1 / Ø5.5 through | mount screws | designed | nema* |

## Sizes

| feature | mm |
|---|---|
| face | 20.2 × 20.2 |
| hole pattern | 16 × 16 |
| holes | 4 × M2 tapped |
| pilot boss | Ø15 × 1.5 |
| shaft | Ø4 × 10 |
| body lengths drawn | 30, 38 |

## Where the files are

- Wikipedia: [Stepper motor](https://en.wikipedia.org/wiki/Stepper_motor) — web — CC BY-SA 4.0 (text)
- NEMA: [ICS 16 motion/position control motors and controls](https://www.nema.org/standards/view/motion-position-control-motors-controls-and-feedback-devices) — PDF — NEMA standard, purchase

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

Index: https://xemstudio.com/files/hardware/nema-8-stepper/index.json

- nema8-30: [STEP](https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-30.step) · [STL](https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-30.stl) — NEMA 8 envelope, 30 mm body, 16.0 mm hole pattern (M2 tapped), Ø4.0 shaft
- nema8-38: [STEP](https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-38.step) · [STL](https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-38.stl) — NEMA 8 envelope, 38 mm body, 16.0 mm hole pattern (M2 tapped), Ø4.0 shaft

## How it fits

### Connects to
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/): four M2 into the face

### Alternatives
- [NEMA 11 stepper motor: 28.2 mm face, 23 mm hole pattern](https://xemstudio.com/objects/nema-11-stepper/): NEMA 11 frame
- [NEMA 14 stepper motor: 35.2 mm face, 26 mm hole pattern](https://xemstudio.com/objects/nema-14-stepper/): NEMA 14 frame

## Questions

**What is the NEMA 8 hole pattern?**

4 × M2 tapped on a 16 × 16 mm square, on a 20.2 mm face.

**What is the NEMA 8 shaft size?**

Ø4 mm as commonly supplied (10 mm out from the Ø15 pilot boss).

**How long is a NEMA 8 stepper?**

The standard fixes the face, not the length. Common bodies: 30, 38 mm; longer bodies give more torque.

## Fits with

- [NEMA 11 stepper motor: 28.2 mm face, 23 mm hole pattern](https://xemstudio.com/objects/nema-11-stepper/)
- [NEMA 14 stepper motor: 35.2 mm face, 26 mm hole pattern](https://xemstudio.com/objects/nema-14-stepper/)
- [Flexible shaft couplers, 5–10 mm bores](https://xemstudio.com/objects/shaft-couplers/)
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/)
- [GT2 timing pulleys, 16T–60T (2 mm pitch)](https://xemstudio.com/objects/gt2-pulleys/)