2GT belts are manufactured by an affiliate company of Gates called "Gates Unitta", in Asia. Gates 2GT belts are using a different profile than GT2/GT3. As they are not 100% compatible with GT2/GT3 they could lead to an increase in backlash and belt wear, specially on a 3D printer.
GT2 and GT3 belts are made by "Gates USA" and are using a different profile than 2GT. GT2 and GT3 share the same profile and are 100% compatible. GT3 name is only for belt, it is a new version with a better construction. There is no GT3 pulleys as this naming is for belt only (pulleys are therefore GT2).
Those belts have probably 2GT profile but with all the naming chaos and unknown source you might have something else. I highly recommend to use genuine Gates belt for such an important part.
pd = P*N / π
O.D. = pd - 2*U
Where
- pd = pitch diameter
- P = belt pitch
- N = number of pulley teeth
- O.D. = pulley outside diameter
- U = Distance from Pitch Line to Belt Tooth Bottom
- U = 0.254mm for 2GT and GT2/3 2mm pitch belts
- U = 0.381mm for 3GT and GT2/3 3mm pitch belts
Example for GT3 2mm pitch and 20T pulley :
pd = 2 * 20 / π = 12.732mmO.D. = 12.732 - 2*0.254 = 12.224mm