CROWN BIT FOR ENHANCING BOREHOLES Russian patent published in 1997 - IPC

FIELD: mining engineering. SUBSTANCE: crown bit consists of mineral-destruction head with central conical passage and of tail with conical tip. On the conical surfaces of crown beat and tail tip, there are semicircle-section spiral grooves with constant pitch. When assembled, spiral grooves form circle-section spiral cavity where conical compression spring of round steel wire is located. Slope angle of conical surfaces of head passage and tail tip ranges from 8 to 15 deg. EFFECT: improved design. 2 cl, 1 dwg