| 摘要 |
A tool and method for use with a drill string or the like in capturing an object in a cavity, such as subterranean borehole, include a mandrel, object engaging apparatus for latching the mandrel to the object as the tool is moved into the borehole, and string engaging apparatus for keeping the mandrel latched to the drill string as the mandrel is moved into the borehole and for unlatching the mandrel from the drill string when the drill string is rotated in a first direction with the mandrel latched to the object. A washover pipe and mill, which are connected to the drill string, may be moved into contact with the object after the mandrel is unlatched from the drill string for milling through the object. A ratchet allows the mill to move toward the object relative to the mandrel and prevents the mill from moving away from the object relative to the mandrel. The ratchet allows the mill to move away from the object when the drill string is rotated in the first direction and lifted relative to the mandrel. The string engaging assembly relatches the mandrel to the drill string when the drill string is moved away from the object and rotated in a second direction. The object engaging apparatus unlatches the mandrel from the object when the mandrel is moved away from the object and rotated in the second direction.
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