An apparatus and methods are disclosed for retrofitting a manual benchtop milling machine utilizing servo controls and/or stepper motors. The present disclosure provides a retrofit kit for the modification of a milling machine by incorporating ball screws and ball nuts without removing or replacing the original acme nuts, which inherently have been properly configured and aligned to the machine on which they were originally installed. The retrofit kit of the present disclosure allows for the modification using the alignment of the original acme nuts in their proper location and alignment obviating the need for custom machining or alignment.