FIELD: drill tool for drilling noncircular blast-holes. SUBSTANCE: drill crown includes a case with internal cavity and working surface with cylindrical/spherical insertion pieces and a system of blast off openings. Apexes of periphery insertion pieces are placed so to form geometric figures with straight sides. In so doing not less than three insertion pieces are placed in line at each side of geometric figure. EFFECT: high efficiency. 4 dwg
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