In this paper, the construction is elaborated in detail, but also the production of the toothed wheel assembly, which is often used in hydroelectric power plant engine rooms, is analyzed in order to measure the rotational speeds of the rotating elements of the turbine and generator assembly. Such measurement is performed for various purposes, but the most important one is singled out - for the purpose of the turbine safety system, ie to protect it from excessive speed. This is also called overspeed or escape protection, whose two systems (electrical and mechanicalhydraulic) are described here. As can be seen from the title that the emphasis is placed on milling processes during production, the paper also touched on its theoretical part, ie its mutual divisions and characteristics, all supported by a series of images and examples to facilitate understanding and visualization of individual procedures. The technological preparation of the production of the toothed wheel goes through all phases of designing the technological process and explains the most important speeds and feeds (ie cutting speed and feed rate), and then briefly shows the creation of its position in the software "SolidWorks" with the upgrade of "CamWorks". The work ends with the calculation of the spring (under the action of centripetal force) so that it can be properly dimensioned, all for the successfully developed construction and operation of the assembly with a mechanically activated hydraulic valve. In the attachments there is a detailed construction of the toothed wheel. These drawings, as well as several others within the final work, were made using softwares like SolidWorks for 3D and AutoCAD for 2D models.