Bore hole opener

摘要: A bore hole opener for enlarging a includes longitudinal body, duct drilling fluid, formed longitudinally in the having fluid passage cross-section of inside radius i, and at least two hole-opening arms, borne by which have an active part equipped with cutting mechanisms, are arranged therein such way that they can slide between position rest body partially out guided supported this purpose over distance g which, position, project from length o, values o chosen to simultaneously satisfy conditions i+g+o S; 0.30