# Ping-pong ball Ø40 mm, 0.4 mm wall

> What size is a ping-pong ball?

- Category: Hardware › Found & household materials
- Kind: Standard part
- Basis: ITTF table-tennis ball: Ø40.0, 2.7 g; drawn as a hollow sphere with a 0.4 mm wall
- Page: https://xemstudio.com/objects/ping-pong-ball/ · JSON: https://xemstudio.com/api/geometry?object=ping-pong-ball · Plain text: https://xemstudio.com/objects/ping-pong-ball/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- A table-tennis ball is Ø40.0 mm and weighs 2.7 g (ITTF).
- The file is a hollow sphere: Ø40.0 outside, 0.4 mm wall (Ø39.2 inside).
- At 2.7 g it is the lightest ready-made hollow sphere of that size, which makes it useful as a displacer in small demonstrator engines.

## Sizes

| ball | od_mm | wall_mm | mass_g |
|---|---|---|---|
| table-tennis ball | 40.0 | 0.4 | 2.7 |

## Where the files are

- Wikipedia: [Craft stick](https://en.wikipedia.org/wiki/Craft_stick) — web — CC BY-SA 4.0 (text)
- Wikipedia: [BB gun](https://en.wikipedia.org/wiki/BB_gun) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Table tennis](https://en.wikipedia.org/wiki/Table_tennis) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine builds (videos and write-ups)](https://longearthsociety.com/engineering/) — web, video — LES site

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

Index: https://xemstudio.com/files/hardware/ping-pong-ball/index.json

- ping-pong-ball-40mm: [STEP](https://xemstudio.com/files/hardware/sticks-skewers-wire-bbs/ping-pong-ball-40mm.step) · [STL](https://xemstudio.com/files/hardware/sticks-skewers-wire-bbs/ping-pong-ball-40mm.stl) — table-tennis ball Ø40.0, 0.4 mm wall, 2.7 g

## How it fits

### Goes in or on
- [Can-engine cap for 53.3, 58, 66 and 76.2 mm cans](https://xemstudio.com/objects/can-engine-cap/): lightweight displacer in a small demonstrator

### Alternatives
- [Glass marbles 1/2 in, 5/8 in and Ø16 mm](https://xemstudio.com/objects/glass-marbles/): a solid Ø16 ball

## Questions

**What is the diameter of a ping-pong ball?**

40.0 mm (ITTF), weighing 2.7 g.

**How thick is a ping-pong ball wall?**

About 0.4 mm; the file is drawn with a 0.4 mm wall, Ø39.2 inside.

## Fits with

- [Glass marbles 1/2 in, 5/8 in and Ø16 mm](https://xemstudio.com/objects/glass-marbles/)
- [BBs: steel Ø4.5 mm (.177) and airsoft Ø6.0 mm](https://xemstudio.com/objects/steel-and-airsoft-bbs/)
- [Borosilicate test tubes, 10×75 to 30×200 mm](https://xemstudio.com/objects/borosilicate-test-tubes/)
- [Can-engine cap for 53.3, 58, 66 and 76.2 mm cans](https://xemstudio.com/objects/can-engine-cap/)