Gears
thingiverse
These gears work well with 6mm shafts and more options are on their way. Ensure you don't resize them, as altering the shaft size would affect their compatibility.
Download Model from thingiverse
With this file you will be able to print Gears with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Gears.