The surface of cutters for dentistry is rendered passive to electroplating by immersion in a concentrated aqueous solution of nitric acid for a certain period of time. This is followed by painting a length including the surface marked out by the slots, the surface inside the slots and the surface at the tip, using an electrically insulating paint resistant to acids. Each cutter is then ground using a grinding wheel with rotating disk having an abrasive edge shaped like the continuous profile of the painted surface. Grinding removes the paint together with a micrometric layer of metal from the surface except for that inside the slots. The shank is ground and painted for a length adjacent to the slots. Further processes are then carried out in the following order: activation of the exposed metal surface by electrolysis of reversed polarity in a Wood bath; initial electrolytic nickel-plating in a Wood bath; application of a powdered diamond coating in a Watts bath by a second process of electrolytic nickel-plating containing powdered diamond in contact with the cutters; stabilization of the diamond coating by a third process of electrolytic nickel-plating in a Watts bath containing no powdered diamond; removal of the residual insulating paint by immersing the cutters coated with powdered diamond in a non-halogenous solvent treated with ultrasounds.