The work presents a study of surface roughness of pieces of magnesium UNS M11311 obtained by dry turning. The study is focused in repair operations of this type of materials when they are used as inserts of metalic hybrid components. Therefore, the main limitations of this research are the values of the cutting conditions used; especially low in comparison with the usually values of these parameters used in the production of the magnesium. The followed methodology consists of a series of tests of dry horizontally turning carried out with tools of different coatings and under different cutting conditions. The design of experiments has been made by means of fractional factorial orthogonal designs and the analysis of the results by the ANOVA method. The principal result is one ranking for the combinations of cutting conditions and tool coatings based on the surface roughness expected given by the mathematical model. As first conclusion, it is possible to affirm that, the best surface finishes are obtained for low feeds. Cutting tools used in the machining of other types of materials (steel, stainless steel) can be used obtaining a quality of the surface finish similar to that obtained with tools for specific use of non-ferrous metals.