US Patent 7237617 Disengageable downhole tool

A disengageable downhole tool (10) for use in the oil and gas industry. The tool can be decoupled from a work string to allow further tools to be operated from the work string on being run deeper into a well. The tool is then picked-up by the work string on retrieval from the well. In one embodiment a milling tool (28, 32) is described having a hex-drive system for operation of the tool from the work string with coupling and decoupling being achieved via shear pins (40) and a mating ledge and shoulder.