Patent ID: 8851205

Claim:
An apparatus for use on a drill string for increasing the drift diameter of a well bore during drilling, comprising: a substantially cylindrical first reamer having a plurality of cutting blades extending a distance radially outwardly from the outer surface of the reamer, wherein, in an order counter to the direction of rotation, a first cutting blade extends a first distance and each additional cutting blade extends an equal or greater distance than the preceding cutting blade, the plurality of blades defining a curved cutting area extending approximately 50% of the circumference of each reamer; a substantially cylindrical second reamer having a plurality of cutting blades extending a distance radially outwardly from the outer surface of the reamer, wherein, in an order counter to the direction of rotation, a first cutting blade extends a first distance and each additional cutting blade extends an equal or greater distance than the preceding cutting blade, the plurality of blades defining a curved cutting area extending approximately 50% of the circumference of each reamer; wherein the plurality of cutting blades of the second reamer are angularly displaced 180 degrees from the plurality of cutting blades of the first reamer about the axis of rotation of the drill string.