Surfaces of huge square or rectangular flanges can be linear machined, using a in-situ X-Y axes machine. This is basically a vertical machine, mounted on the horizontally resting square tubes through hydraulic cylinders. The hydro-motor driven milling head, with its quill movement for depth of cut setting, is mounted on the cross beam. The milling head moves along the cross beam left to right and right to left in X axis. The cross beam moves up and down (Y axis) along the two vertical beams on either side of the flange. The linear guideways are provided with linear motion guideways and the movements are motorized lead screws. This machine is under development.