A bandsaw assembly for cutting large diameter workpieces such as turbine rotors, heat exchangers or shafts at a plant or factory and a method of using the same is disclosed. The assembly includes a frame; ground-engaging wheels or a track provided on the frame; a plurality of spaced apart towers extending vertically upwardly from the frame; a rotatable drive wheel mounted on each tower, said drive wheel being horizontally oriented and presenting a vertically oriented circumferential surface; a motor operatively engaged with one or more of the drive wheels; and a bandsaw blade passing around the wheels and being in contact with the circumferential surfaces thereof; said blade being selectively driven by the drive wheels. The towers are variable in length to raise or lower the blade. The assembly is reduced in width for transportation or storage and increased in width for operation.