Apparatus and method for drilling generally horizontal underground boreholes

A method comprising steps of:

• providing a pilot tube within an underground pilot hole having a pilot hole diameter;
• rotating and moving forward a cutter head and a casing extending rearwardly from the cutter head to cut an underground borehole;
• wherein the borehole follows the pilot hole and has a borehole diameter larger than the pilot hole diameter;
• moving pressurized air rearwardly through a cutter head air passage formed in the cutter head and a casing cuttings passage formed in the casing to discharge cuttings created by the cutter head out of a rear end of the casing;
• and wherein the step of moving pressurized air comprises moving pressurized air rearwardly through a pilot tube air passage formed in the pilot tube.

An apparatus comprising:

• an earth-boring cutter head;
• a swivel located forward of and adjacent the cutter head;
• a swivel air passage formed in the swivel;
• a cutter head air passage extending through the cutter head;
• said cutter head air passage being in fluid communication with the swivel air passage;
• and wherein pressurized air flows rearwardly from the swivel air passage and into the cutter head air passage;
• a casing secured to the cutter head and extending rearwardly therefrom so that the casing and cutter head are rotatable together as a unit, the casing having a casing front end and a casing back end;
• a casing cuttings passage which extends from adjacent the casing front end to adjacent the casing back end and which is in fluid communication with the cutter head air passage;
• and
• an entrance opening of the casing cuttings passage which is adjacent the cutter head, spaced from the cutter head air passage and adapted to allow cuttings to move through the entrance opening into the casing cuttings passage.