Abstract The paper deals with the issue of cutting edge preparation and tool treatment before coating. In this article, the novel method called edge preparation by plasma discharges in electrolyte is presented. The mechanism of material removal is based on melting and vaporisation instead of abrasion and it is not influenced or limited by the hardness of the tool material. The shape of the vapour-plasma envelope leads to intensive material removal from the edges of cutting tools. This phenomenon was applied to round the sharp edges of electrically conducting cutting tools. The tested cutting tool material of samples was cemented carbide. The cutting edge radii were formed by immersing the cutting tool into an electrolyte. The increasing the processing time results in a larger cutting edge radius. The values of cutting edge radii increased from 10 μm to 45 μm in 50 s of treatment by plasma discharges in electrolyte. Moreover, the grinding marks on the surfaces of the cemented carbide turning insert prepared by plasma discharges in electrolyte were smoothed. The quality of surface roughness of cemented carbide samples was increased. If cemented carbide turning inserts are prepared using plasma discharges in electrolyte after grinding then the values of surface roughness parameter Ra will be lower from 0.223 μm to 0.186 μm in the cross direction to the grinding marks and from 0.183 μm to 0.117 μm in the longitudinal direction.