This paper presents the results of experimental studies of the relationship between surface roughness and technological parameters when cutting copper alloys JI62, JIC59-1, aluminum JI.16T, AlMg2, stainless steel SUS201, SUS304 on lathe CNC PLG42. Based on theory and experiment of 6 marks of above alloy, from the actual measured data on roughometer POCKETSURF of America, experimental planning method given mathematical function describing each relationship between surface roughness and cutting parameters on CNC lathes PLG42. Scientific research results can be used as a basis for the study other aspects of the cutting process, design support, software programming control cutting. In terms of practical research results used as the reference for the technology, in the mining process and used CNC lathes can adjust your cut to achieve surface roughness details on request requirements. The experimental results have been applied in production efficiency in Chemical Company Limited 21-General Department of Defence Industry, Ministry of Defense, surface quality guaranteed products, textile production increased clearly.