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GT3 (3GT, 3 mm pitch) timing pulleys: pitch diameter and outside diameter, 16T to 80T
What is the pitch diameter and outside diameter of a GT3 (3GT, 3 mm pitch) timing pulley with N teeth? · Standard part · basis: PD = 3 N / pi; OD = PD − 0.762 mm, checked on two 20-tooth pulleys (KSC Direct / SDP, RatRig); other rows are the rule, not a maker table
Also called: gt3 pulley dimensions, 3gt pulley outside diameter, gt3 pulley 20 tooth, gt2-3m pulley, 3gt pulley 20t diameter, 3mm pitch pulley pitch diameter, gt3 vs gt2, gt3 pulley od formula
Exact dimensions. True size, with no tolerance added.
- sizes
- 15 in table
Notes
- GT3 / 3GT (3 mm pitch, also sold as GT2-3M): PD = teeth x 3 / pi. OD = PD − 0.762 mm, i.e. a pitch-line differential of 0.381 mm. That rule rests on two 20-tooth pulleys from two sellers: SDP/SI part 20-3P06M6FA6 via KSC prints PD 19.1 / OD 18.3 (flange Ø22.7, 6 mm belt, 6 mm bore) and RatRig's 9 mm pulley prints PD 0.752 in / OD 0.722 in (19.10 / 18.34 mm; hub 0.5 in, overall width 0.813 in, 1/4 in bore). No GT3 table of other tooth counts was readable, so the other rows apply the rule and are not maker values.
- Belt moves 3 mm per tooth: a 20T pulley moves 60 mm per turn (on a 200-step motor at 16x microstepping that is 3200 / 60 = 53.3 microsteps per mm).
- Sellers list 3 mm pulleys as 'for GT2 or GT3 belts' (KSC) and as 3GT / GT2-3M (RatRig); check the profile printed on the pulley you buy.
- No files: the GT3 tooth form is not published in any source read, and a made-up groove would not mesh.
GT3 (3GT, 3 mm pitch) timing pulleys: pitch diameter and outside… size chart
| teeth | pitch Ø PD, mm | outside Ø OD (PD − 0.762), mm | belt travel per turn, mm |
|---|---|---|---|
| 16 | 15.28 | 14.52 | 48 |
| 18 | 17.19 | 16.43 | 54 |
| 20 | 19.10 | 18.34 | 60 |
| 22 | 21.01 | 20.25 | 66 |
| 24 | 22.92 | 22.16 | 72 |
| 28 | 26.74 | 25.98 | 84 |
| 30 | 28.65 | 27.89 | 90 |
| 32 | 30.56 | 29.80 | 96 |
| 36 | 34.38 | 33.62 | 108 |
| 40 | 38.20 | 37.44 | 120 |
| 44 | 42.02 | 41.25 | 132 |
| 48 | 45.84 | 45.07 | 144 |
| 60 | 57.30 | 56.53 | 180 |
| 72 | 68.75 | 67.99 | 216 |
| 80 | 76.39 | 75.63 | 240 |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| KSC Direct (SDP/SI part 20-3P06M6FA6) | 3 mm pitch 20-tooth timing pulley, 6 mm belt, 6 mm bore: PD 19.1, OD 18.3, flange 22.7 | web | Publisher's page; dimensions are facts |
| RatRig | 3GT (GT2-3M) 20-tooth pulley, 9 mm belt, 1/4 in bore: PD 0.752 in, OD 0.722 in, hub 0.5 in, overall 0.813 in | web | Publisher's page; dimensions are facts |
| Pfeifer Industries | Timing belt pulley PD / OD charts: PD = pitch x teeth / pi, OD = PD - 2 U (U = cord to tooth root) | web | Publisher's page; dimensions are facts |
Xem scan
File coming
No downloadable true-size file yet: the published figures do not fix the whole shape, and Xem never guesses a number. A measured scan is planned; request it and it moves up.
https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.Plain text: sheet.txt · JSON: /api/geometry?object=gt3-timing-pulleys-3mm-pitch
Fits with
Questions
What is the outside diameter of a 20 tooth GT3 pulley?
18.34 mm: pitch diameter 19.10 mm minus 0.762 mm.
How far does a GT3 belt move per tooth?
3 mm; a 20T pulley moves the belt 60 mm per revolution.
Is GT3 the same as 3GT?
Sellers use 3GT, GT3 and GT2-3M for the same 3 mm profile; the numbers above are for it.