Drag Type Under Reamer

The drag-type under reamer (DTU) is de- signed to run in conjunction with a drill bit or a bullnose, depending on pilot hole condition or project objectives. The DTU’s three retractable cutting arms are opened and held in position by continuous hydraulic pressure. Cutters are retracted by disengaging the pump, allowing the tool to be repositioned for selective under reaming operations or retrieval from the well. This simple and efficient design, with each arm ma- chined out of a single piece of high-strength alloy, ensures longer tool time at bottom and easy field maintenance.