Miroshnichenko O. Increase of efficiency of machining of through holes by the combined tool.

An object is machining of holes by combined tool. A purpose is an increase of efficiency of machining of holes by means the optimization of cutting conditions and geometrical parameters of combined tool. Methods - knowledge's from the theory of cutting (model of chip ascent and model of formation of unroundness), material strength (model of transversal displacement of tool axis), and also methods of geometrical and linear programming at determination of the optimum cutting conditions. Novelty - it is developed the mathematical the model of chip descent which takes into account influence of geometrical parameters of axial tool and physical-mechanical properties of the material being machined, and also it is developed the mathematical model of formation of unroundness at the parallel scheme of machining of holes by combined tool core drill-reamer. Results - it is offered the method of machining of holes by combined tool core drill-reamer, that allows to decrease unroundness of machined holes in 5 - 10 times by comparison to unidimensional tool, and also to reduce a roughness due to the exception of contact of chip with machined surface. Industry is machine-building plants of Ukraine.