Remotely operable hydraulic underreamer

An underreamer comprising:

• an underreamer body;
• first and second cutter assemblies slidably disposed within the body for selective movement between a collapsed position and a radially extended position;
• each said cutter assembly presenting a fluid pressure receiving area and movable from the collapsed position to the radially extended position upon application of fluid pressure to said fluid pressure receiving area;
• a cutter return assembly for urging at least one of said cutter assemblies from the radially expanded position to the collapsed position, the return assembly comprising a spring-biased return plunger having a translation surface adapted to contact a portion of one of said cutter assemblies and urge said assembly downwardly and to permit lateral translation of the cutter assembly with respect to the return plunger;
• a pair of cutter assembly guides which help align the cutter assembly as it is expanded and contracted
• wherein the pair of cutter assembly guides comprise:
• a first guide disposed above the cutter assembly;
• and
• a second guide disposed below the cutter assembly.

An adjustable underreamer comprising:

• an underreamer body having a longitudinal axis;
• a cutter assembly disposed within the body and selectively movable between a collapsed position and a radially expanded position, the cutter assembly having at least one cutter;
• and
• an adjustment member of the cutter assembly to locate the cutter a predetermined radial distance from the axis when the cutter assembly is moved to its radially expanded position, said adjustment member being adjustable on said underreamer body to adjust said predetermined radial distance.

An adjustable underreamer comprising:

• an underreamer body having a longitudinal axis;
• a cutter assembly slidably disposed within the body and selectively movable between a collapsed position and a radially expanded position, the cutter assembly having at least cutter;
• and
• an adjustment member of the cutter assembly to locate the cutter at a predetermined radial distance from the axis when the cutter assembly is moved to its radially expanded position;
• and
• wherein the cutter assembly comprises a rotable cutter which is affixed to the cutter assembly at two points.

An adjustable underreamer comprising:

• an underreamer body having a longitudinal axis;
• a cutter assembly disposed within the body and selectively movable between a collapsed position and a radially expanded position, the cutter assembly having at least one cutter;
• and
• an adjustment member of the cutter assembly to locate the cutter at a predetermined radial distance from the axis when the cutter assembly is moved to its radially expanded position;
• a cutter assembly support comprising:
• a support body;
• and
• an angled cutter assembly alignment track disposed within the support body to engage a generally complimentary alignment track on said cutter assembly.

An adjustable underreamer comprising:

• an underreamer body having a longitudinal axis;
• a cutter assembly slidably disposed within the body and selectively movable between a collapsed position and a radially expanded position;
• said cutter assembly comprising:
• a body;
• a bearing attached to said body at each end;
• and
• a cutter rotatably attached to said bearing.