Mechanical design concepts are presented for a new desktop meso-milling CNC machine. Concept selection criteria are discussed which highlight some of the challenges in mechanical configuration design, instrumentation and control. In conjunction, the conversion of an existing production 3-axis desktop milling machine into a meso-milling CNC machine is detailed. The retrofit process, which features electrical as well as mechanical design, control and instrumentation setup, helps to identify the design problems which must be solved, when creating a new desktop meso-milling machine tool which offers improved resolution, accuracy and repeatability while facilitating manufacturing flexibility.