Abstract: A dragline is constructed in the manufacturing plant with a segmented guide rail shimmed and secured to the plates of a tub concentric with the pintle for the deck. The guide rail is then machined so that a rolling surface is created on the rail that is within .+-.0.002 inches of a planar surface. Tub gear segments have mounting portions accurately machined and accurately drilled as are tub rail segments and deck rail segments accurately machined. The dragline is then disassembled, shipped to the site and re-erected with the guide rail shimmed and installed on the plates of the tub so that the rolling surface is within .+-.0.002 inches of a plane. The deck is mounted on the pintle and supported on columns to space the deck rail girder from the tub rail girder. A tram or boom is mounted on the deck pintle and has a machine tool carriage riding on the guide rail so that a milling head on the carriage can mill the upper and lower rail girders to within .+-.0.0025 inches of planar.