Abstract: A precision positioning system is used for resurfacing and repairing rails and guideways of large, heavy machinery at users facilities. The system has new components, an entire machining system, a new alignment system, parallel platforms for tool support and surface scanning. A sectioned, portable monorail frame is held by fixed supports at the locus of a heavy machine requiring guideway straightening. Fixed guides extend along the outer surface of the monorail. Guide wheels and drive wheels contact the guides and support and move an outer tubular beam carriage. An assembly of machining tools is adjustably positioned on the carriage. Laser alignment sources and sensors are connected to the carriage and to heavy machines off-axis and parallel to the monorail. Intelligent controls precisely position the tools for resurfacing the rails and guideways. Scanning and a printout of machine guideway accuracy, before and after the operation, provide written verification of quality improvement.