The trend of using micro-parts in modern industry puts new tasks for contemporary production technologies. If these parts are made of difficult-to-machine materials, machining problems become more complicated. On the other hand, the requirements go towards manageable and stable production processes, reduction of the processes number, reduction of the machining cost, using of clean technologies, etc. Use of mechanical solid tools in engineering materials micro-machining, many problems occur, such as: high machined surface roughness of the, tool deflection, intensive tool wear, etc. These problems lead to difficulties in establishing adequate process models, and thus the ability to control of micro-milling process and it’s including in smart processes and smart factory concepts. This paper presents the possibilities of using micro-milling in the difficult-to-process materials machining. The phenomena in micro-cutting are analysed, as well as the output machinability indicators (surface roughness, tool wear, etc.). As a conclusion, guidelines and technological frameworks for the application of micro-milling in practice are given.