FIELD: drilling engineering. ^ SUBSTANCE: tool comprises housing provided with operation member and thread and calibrator mounted on the pin of the housing between the operation member and thread. The operation member is made of drill bit with shifted axes. The pin is inclined to the axis of the housing and is stepped. The point of intersection of the axis of the pin with the axis of the housing is in coincidence with the axis of the drill bit. The axis of the pin is perpendicular to the line that connects the points of a contact of the rotary bit with the wall of the well. The calibrator is made of several rotary bits each of which is mounted on the individual step of the pin and is spring-loaded in the axial direction. The spring is mounted from the side of the top face of the rotary bits. ^ EFFECT: enhanced reliability. ^ 2 dwg
