How can I connect a 6mm motor shaft to a 15mm disc shaft?

[Silwal]

Hello,
I am on a project where i need to rotate a disc with the help of electric motor(connecting directly to the shaft of the motor). The motor shaft has a diameter of 6mm and the shaft of disc has 15mm. what could be the best possible way to connect both of them.

 

[billy_joule]

There are a lot of choices out there:
https://en.wikipedia.org/wiki/Coupling

Which will best suit your application will depend on your system & requirements.