I am cheaper than most here but I reckon the motor driving the mill is not a place to save dollars or use scrap.
Open motors will invariably make sparks as they operate + fine dust from an accident with the mill jar during its un attended 8 hour turning (the lid comes off - bearing fails- spindle rubs a hole in the drum - ) I paid a bit over a hundred for a new sealed motor that I can use elswhere if needed, I set the whole deal up on an old table with a long slack vee belt drive so the motor is three feet away from the drum. Pictures of those little mills with the motor just a few inches directly under the drum make me nervous.
Not a problem until something goes astray.