A guide tube pitch adjustment apparatus for aligning distal ends of lance guide tubes in registry with tube openings in a heat exchanger tube sheet is disclosed. A guide tube pitch clamp assembly carried within and supported from a housing. The pitch clamp assembly has at least two V-blocks fastened to a threaded rod. One V-block is fastened to a portion of the threaded rod having right hand threads, and another V-block is fastened to another portion of the threaded rod having left hand threads. Each of the V-blocks supports a portion of one of the guide tubes, and a cross bar clamp within the housing is oriented to span across the V-blocks and adjustably hold the portions of the guide tubes in a spaced relationship such that spacing between the distal ends of adjacent guide tubes may be adjusted by rotation of the threaded rod.