1. Field of Invention
The invention is directed to downhole milling tools utilized in oil and gas wells to abrade, cut, or mill an object within the well and, in particular, to downhole cutting tools having a blade that is retracted during run-in and extended radially outward for cutting, abrading, or milling.
2. Description of Art
In the drilling, completion, and workover of oil and gas wells, it is common to perform work downhole in the wellbore with a tool that has some sort of cutting profile interfacing with a downhole structure. Examples would be milling a downhole metal object with a milling tool or cutting through a tubular with a cutting or milling tool. To facilitate these operations, cutting elements are disposed on the downhole cutting tool. In one type of milling tool, the cutting elements are disposed on blades that can be disposed in a retracted position and an extended position. In certain of these embodiments, the blades are extended by increasing the pressure across the tool. Upon reduction of the pressure, such as after the milling operation has been completed, the blades are moved back to their retracted position so that the tool can be retrieved from the well.