A hole opener for placement in a drill string having a body generally comprising a collar, a triangular mid-section, a triangular shaped pilot and a bull nose. The collar provides means for attaching the tool body to the drill string. The triangular mid-section has three longitudinal, radially spaced apart blade members that are parallel to the central axis of the tool body so that the blades can cut into the walls of the bore hole to enlarge the size of the bore hole. Three annular flow zones span the distance between the blade members so that fluids and cuttings can circulate through the bore hole. The pilot section also has three longitudinal, radially spaced apart blade members that are parallel to the central axis of the tool body bore and three annular flow zones which span the distance between the blade members of the pilot. The pilot section is downhole from the mid-section. The outer diameter of the blades of the pilot section are substantially less than the outer diameter of the blades of the mid-section, thus allowing the hole to be enlarged gradually. A bull nose downhole of the pilot section and of an outer diameter somewhat less than the inner diameter of the bore hole guides the drill string through the bore hole. The collar, mid-section, pilot section and bull nose are integral portions of the tool body.