The relevance. Many years of experience in directional drilling has made it possible to identify complex mining and geological conditions in which the use of deflectors leads to decrease in the effectiveness of the curvature and accidents. So, for example, the fastening of continuous deflectors in hard, very hard and abrasive rocks, when the borehole diameter has minimum development along the borehole diameter, leads to jamming of the rock cutting tool. In this case, it is difficult to improve the efficiency of diverters due to the lack of special technical means and effective technologies for deviating wells, which makes the problem of reducing the efficiency of diverters relevant and needs to be addressed. The main aim: search for the causes of jamming of asymmetric and combined diverters when setting and breaking out in wells drilled in hard rocks; development of a diamond drill bit design with a special layout of lateral and end cutting structure; assessment of the effect of eccentricity of the cutting part of a drilling tool on the efficiency of drilling a wellbore according to diameter. Object: eccentricity of the cutting part of the drilling tool. Methods: collection, analysis and generalization of the data in literary sources, analytical research and experimental work. Results. The paper describs the causes of the whipstock jamming in the well and introduces the existing technologies that allow solving the given problem. The authors developed a diamond drill bit of special design and described the principle of its operation. The influence of the cutting part eccentricity on drilling the hole in diameter is assessed and the fact of increasing the milling ability is established.