# Spur gears, module 2.5: 10 to 80 teeth (20° involute)

> What is the pitch diameter of a module 2.5 spur gear?

- Category: Hardware › Motion
- Kind: Hardware
- Basis: ISO 53 basic rack: 20° pressure angle, addendum m, dedendum 1.25 m; pitch Ø = m × teeth, tip Ø = m × (teeth + 2), root Ø = m × (teeth − 2.5)
- Page: https://xemstudio.com/objects/spur-gears-module-2-5/ · JSON: https://xemstudio.com/api/geometry?object=spur-gears-module-2-5 · Plain text: https://xemstudio.com/objects/spur-gears-module-2-5/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.** True size, with no printing tolerance added.

## Notes

- Centre distance of two module 2.5 gears = m × (N1 + N2) / 2. Face width 20 mm, plain bore (add a hub, key or set screw to suit). Teeth below 17 are drawn without profile shift, so they undercut as real unshifted gears do.

## Sizes

| teeth | pitch_dia_mm | tip_dia_mm | root_dia_mm | face_mm | bore_mm |
|---|---|---|---|---|---|
| 10 | 25.0 | 30.0 | 18.75 | 20.0 | 7 |
| 12 | 30.0 | 35.0 | 23.75 | 20.0 | 8 |
| 14 | 35.0 | 40.0 | 28.75 | 20.0 | 10 |
| 15 | 37.5 | 42.5 | 31.25 | 20.0 | 11 |
| 16 | 40.0 | 45.0 | 33.75 | 20.0 | 12 |
| 18 | 45.0 | 50.0 | 38.75 | 20.0 | 14 |
| 20 | 50.0 | 55.0 | 43.75 | 20.0 | 15 |
| 22 | 55.0 | 60.0 | 48.75 | 20.0 | 17 |
| 24 | 60.0 | 65.0 | 53.75 | 20.0 | 19 |
| 25 | 62.5 | 67.5 | 56.25 | 20.0 | 20 |
| 28 | 70.0 | 75.0 | 63.75 | 20.0 | 22 |
| 30 | 75.0 | 80.0 | 68.75 | 20.0 | 24 |
| 32 | 80.0 | 85.0 | 73.75 | 20.0 | 25 |
| 35 | 87.5 | 92.5 | 81.25 | 20.0 | 25 |
| 36 | 90.0 | 95.0 | 83.75 | 20.0 | 25 |
| 40 | 100.0 | 105.0 | 93.75 | 20.0 | 25 |
| 42 | 105.0 | 110.0 | 98.75 | 20.0 | 25 |
| 45 | 112.5 | 117.5 | 106.25 | 20.0 | 25 |
| 48 | 120.0 | 125.0 | 113.75 | 20.0 | 25 |
| 50 | 125.0 | 130.0 | 118.75 | 20.0 | 25 |
| 56 | 140.0 | 145.0 | 133.75 | 20.0 | 25 |
| 60 | 150.0 | 155.0 | 143.75 | 20.0 | 25 |
| 64 | 160.0 | 165.0 | 153.75 | 20.0 | 25 |
| 70 | 175.0 | 180.0 | 168.75 | 20.0 | 25 |
| 72 | 180.0 | 185.0 | 173.75 | 20.0 | 25 |
| 80 | 200.0 | 205.0 | 193.75 | 20.0 | 25 |

## Where the files are

- ISO: [ISO 53 standard basic rack (20° pressure angle, addendum 1 m, dedendum 1.25 m) and ISO 54 modules](https://www.iso.org/standard/5768.html) — standard — ISO; dimensions are facts (verify at link)

## Free STEP/STL (26 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/spur-gears-module-2-5/index.json

- gear-m2-5-10t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-10t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-10t.stl) — module 2.5, 10 teeth: pitch Ø25, tip Ø30, root Ø18.75, face 20, bore Ø7
- gear-m2-5-12t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-12t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-12t.stl) — module 2.5, 12 teeth: pitch Ø30, tip Ø35, root Ø23.75, face 20, bore Ø8
- gear-m2-5-14t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-14t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-14t.stl) — module 2.5, 14 teeth: pitch Ø35, tip Ø40, root Ø28.75, face 20, bore Ø10
- gear-m2-5-15t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-15t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-15t.stl) — module 2.5, 15 teeth: pitch Ø37.5, tip Ø42.5, root Ø31.25, face 20, bore Ø11
- gear-m2-5-16t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-16t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-16t.stl) — module 2.5, 16 teeth: pitch Ø40, tip Ø45, root Ø33.75, face 20, bore Ø12
- gear-m2-5-18t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-18t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-18t.stl) — module 2.5, 18 teeth: pitch Ø45, tip Ø50, root Ø38.75, face 20, bore Ø14
- gear-m2-5-20t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-20t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-20t.stl) — module 2.5, 20 teeth: pitch Ø50, tip Ø55, root Ø43.75, face 20, bore Ø15
- gear-m2-5-22t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-22t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-22t.stl) — module 2.5, 22 teeth: pitch Ø55, tip Ø60, root Ø48.75, face 20, bore Ø17
- gear-m2-5-24t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-24t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-24t.stl) — module 2.5, 24 teeth: pitch Ø60, tip Ø65, root Ø53.75, face 20, bore Ø19
- gear-m2-5-25t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-25t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-25t.stl) — module 2.5, 25 teeth: pitch Ø62.5, tip Ø67.5, root Ø56.25, face 20, bore Ø20
- gear-m2-5-28t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-28t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-28t.stl) — module 2.5, 28 teeth: pitch Ø70, tip Ø75, root Ø63.75, face 20, bore Ø22
- gear-m2-5-30t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-30t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-30t.stl) — module 2.5, 30 teeth: pitch Ø75, tip Ø80, root Ø68.75, face 20, bore Ø24
- gear-m2-5-32t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-32t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-32t.stl) — module 2.5, 32 teeth: pitch Ø80, tip Ø85, root Ø73.75, face 20, bore Ø25
- gear-m2-5-35t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-35t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-35t.stl) — module 2.5, 35 teeth: pitch Ø87.5, tip Ø92.5, root Ø81.25, face 20, bore Ø25
- gear-m2-5-36t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-36t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-36t.stl) — module 2.5, 36 teeth: pitch Ø90, tip Ø95, root Ø83.75, face 20, bore Ø25
- gear-m2-5-40t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-40t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-40t.stl) — module 2.5, 40 teeth: pitch Ø100, tip Ø105, root Ø93.75, face 20, bore Ø25
- gear-m2-5-42t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-42t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-42t.stl) — module 2.5, 42 teeth: pitch Ø105, tip Ø110, root Ø98.75, face 20, bore Ø25
- gear-m2-5-45t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-45t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-45t.stl) — module 2.5, 45 teeth: pitch Ø112.5, tip Ø117.5, root Ø106.25, face 20, bore Ø25
- gear-m2-5-48t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-48t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-48t.stl) — module 2.5, 48 teeth: pitch Ø120, tip Ø125, root Ø113.75, face 20, bore Ø25
- gear-m2-5-50t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-50t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-50t.stl) — module 2.5, 50 teeth: pitch Ø125, tip Ø130, root Ø118.75, face 20, bore Ø25
- gear-m2-5-56t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-56t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-56t.stl) — module 2.5, 56 teeth: pitch Ø140, tip Ø145, root Ø133.75, face 20, bore Ø25
- gear-m2-5-60t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-60t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-60t.stl) — module 2.5, 60 teeth: pitch Ø150, tip Ø155, root Ø143.75, face 20, bore Ø25
- gear-m2-5-64t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-64t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-64t.stl) — module 2.5, 64 teeth: pitch Ø160, tip Ø165, root Ø153.75, face 20, bore Ø25
- gear-m2-5-70t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-70t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-70t.stl) — module 2.5, 70 teeth: pitch Ø175, tip Ø180, root Ø168.75, face 20, bore Ø25
- gear-m2-5-72t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-72t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-72t.stl) — module 2.5, 72 teeth: pitch Ø180, tip Ø185, root Ø173.75, face 20, bore Ø25
- gear-m2-5-80t: [STEP](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-80t.step) · [STL](https://xemstudio.com/files/hardware/spur-gears-module-2-5/gear-m2-5-80t.stl) — module 2.5, 80 teeth: pitch Ø200, tip Ø205, root Ø193.75, face 20, bore Ø25

## Questions

**Pitch diameter of a module 2.5, 20-tooth gear?**

50 mm; tip 55 mm.

**Centre distance?**

m × (N1 + N2) / 2: a 20 and a 40 tooth module 2.5 pair sit 75 mm apart.

## Fits with

- [Spur gears, module 0.5: 10 to 80 teeth (20° involute)](https://xemstudio.com/objects/spur-gears-module-0-5/)
- [Spur gears, module 0.8: 10 to 80 teeth (20° involute)](https://xemstudio.com/objects/spur-gears-module-0-8/)
- [Spur gears, module 1: 10 to 80 teeth (20° involute)](https://xemstudio.com/objects/spur-gears-module-1/)
- [Spur gears, module 1.25: 10 to 80 teeth (20° involute)](https://xemstudio.com/objects/spur-gears-module-1-25/)
- [Spur gears, module 1.5: 10 to 80 teeth (20° involute)](https://xemstudio.com/objects/spur-gears-module-1-5/)
- [Spur gears, involute 20°: module 0.5, 1 and 2, 12–60 teeth](https://xemstudio.com/objects/spur-gears-involute/)