[lincpimp]

You can get 6mm bore pinions from sdp/si. They are not hardened so you will have to use a plastic spur. Of have your local machinist turn the shaft down to 5mm. I have done both on these motors. The site I listed has some smaller 13-15 pinions, and 18 and 20. So see if your intended setup can use those sizes, if not get the shaft turned down. Good luck drilling out any hardened pinion, you will need a non-hardened pinion, or al if you want to drill...