An underreamer for forming a cavity within a well bore is provided. The underreamer may include a housing rotatably disposed within the well bore. The underreamer may also include an actuation rod slidably positioned in the housing. The underreamer may further include a plurality of cutter sets where...http://www.google.es/patents/US6644422?utm_source=gb-gplus-sharePatente US6644422 - Pantograph underreamer
