Microtunneling apparatus

A drill string for use with micro tunnelling apparatus having a cutter at a distal end of the drill string and external drive mechanism at a proximal end of the drill string, the drill string being formed by a plurality of connected string segments each string segment having a central axis with a drive shaft aligned along the central axis for rotation there about, an elongate casing that houses the drive shaft, the drive shaft being rotatably mounted within the casing, a first cavity within the casing that extends longitudinally of the casing and offset from drive shaft;

• each string segment includes a front end and a back end longitudinally displaced from the front end, wherein the front end of one string segment is adapted to connect with the back end of another string segment to form the drill string by way of a latch connection, the latch connection being adjustable so as to vary the tolerance between said front end of one string segment and said back end of another string segment while connected, wherein in use the external drive mechanism rotates the drive shaft so as to rotate the drilling head and swarf is removed through said first cavity.