# GT2 timing pulleys, 16T–60T (2 mm pitch)

> What is the outer diameter of a GT2 20 tooth pulley?

- Category: Hardware › Motion
- Kind: Hardware
- Basis: GT2 (2 mm pitch) geometry: pitch diameter = teeth × 2 / π, OD = PD − 0.508 mm; flange and hub sizes typical of printer-kit aluminium pulleys
- Page: https://xemstudio.com/objects/gt2-pulleys/ · JSON: https://xemstudio.com/api/geometry?object=gt2-pulleys · Plain text: https://xemstudio.com/objects/gt2-pulleys/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- Pitch diameter sets the motion: 20T = 12.73 mm PD, so one motor turn moves the belt 40 mm. OD is 0.508 mm less than PD.
- Common bores 5 mm (NEMA 17) and 8 mm (idler shafts). Belt widths 6 mm (standard) and 10 mm (heavier axes).
- Tooth profile in these files is an approximation for fit and clearance, not a belt-grade profile; buy the aluminium pulley for the drive.

## Sizes

| teeth | pitch_dia_mm | od_mm | flange_dia_mm | belt_mm | bore_mm |
|---|---|---|---|---|---|
| 16 | 10.19 | 9.68 | 12.7 | 6 | 5 |
| 20 | 12.73 | 12.22 | 15.2 | 6 | 5 |
| 20 | 12.73 | 12.22 | 15.2 | 6 | 8 |
| 36 | 22.92 | 22.41 | 25.4 | 6 | 5 |
| 40 | 25.46 | 24.96 | 28.0 | 6 | 5 |
| 60 | 38.2 | 37.69 | 40.7 | 6 | 8 |
| 20 | 12.73 | 12.22 | 15.2 | 10 | 5 |

## Where the files are

- Wikipedia: [Timing belt (camshaft)](https://en.wikipedia.org/wiki/Timing_belt_(camshaft)) — web — CC BY-SA 4.0 (text)
- Gates: [PowerGrip GT2 belt and pulley design guide](https://www.gates.com/us/en/power-transmission/synchronous-belts/powergrip-gt2.html) — PDF — Gates site terms (verify at link)

## Free STEP/STL (7 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/gt2-pulleys/index.json

- gt2-16t-5: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-16t-5.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-16t-5.stl) — GT2 16T, bore 5, 6 mm belt; approximate tooth profile, two M3 set screws
- gt2-20t-5: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-20t-5.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-20t-5.stl) — GT2 20T, bore 5, 6 mm belt; approximate tooth profile, two M3 set screws
- gt2-20t-8: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-20t-8.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-20t-8.stl) — GT2 20T, bore 8, 6 mm belt; approximate tooth profile, two M3 set screws
- gt2-36t-5: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-36t-5.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-36t-5.stl) — GT2 36T, bore 5, 6 mm belt; approximate tooth profile, two M3 set screws
- gt2-40t-5: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-40t-5.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-40t-5.stl) — GT2 40T, bore 5, 6 mm belt; approximate tooth profile, two M3 set screws
- gt2-60t-8: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-60t-8.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-60t-8.stl) — GT2 60T, bore 8, 6 mm belt; approximate tooth profile, two M3 set screws
- gt2-20t-5-w10: [STEP](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-20t-5-w10.step) · [STL](https://xemstudio.com/files/hardware/gt2-pulleys/gt2-20t-5-w10.stl) — GT2 20T, bore 5, 10 mm belt; approximate tooth profile, two M3 set screws

## Questions

**What is the diameter of a 20 tooth GT2 pulley?**

Pitch diameter 12.73 mm, outer diameter 12.22 mm, flanges about 16 mm. One revolution moves the belt 40 mm.

**What is the diameter of a 16 tooth GT2 pulley?**

Pitch diameter 10.19 mm, OD 9.68 mm; 32 mm of belt per revolution.

**How far does a GT2 belt move per step?**

With a 20T pulley on a 200-step motor at 16× microstepping: 40 mm / 3200 = 0.0125 mm per microstep (80 steps/mm).

**What size is a GT2 idler?**

Toothed idlers are 16T or 20T on a 3 mm or 5 mm bore bearing; smooth idlers are Ø16–18 mm. A 623 bearing stack (3×10×4) is the common DIY idler.

## Fits with

- [NEMA 17 stepper motor](https://xemstudio.com/objects/nema-17-stepper/)
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/)
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [2020 aluminum extrusion](https://xemstudio.com/objects/2020-extrusion/)
- [T8 lead screw and brass nut (Tr8×8, 2 mm pitch 4-start)](https://xemstudio.com/objects/lead-screw-t8/)