A back reaming tool is disclosed which includes a tool body adapted to be coupled to a drill string, and at least one roller cone rotatably mounted to a leg and having cutting elements disposed thereon. The leg is removably coupled to the tool body. The at least one roller cone is open at only one axial...http://www.google.es/patents/US6729418?utm_source=gb-gplus-sharePatente US6729418 - Back reaming tool
