grinding 6mm shaft to 5mm?

[scarletboa]

what is the best way to grind a 6mm motor shaft to 5mm? my KB45-8xl's shaft is loosening up from the rotor when it heats up and it is almost like the slipper clutch is slipping. i checked and it is for sure the motor. what could i do to fix this?

also, back on topic, my spare motor is a 1400kv KB45-12l. it is a shorter motor than the xl and still has that dang 6mm shaft. i bought the 8xl motor used with the shaft already ground down, but the 12l is brand new with the 6mm shaft.

what is the best way to grind down the motor shaft?