Holroyd manufactured one of the world’s biggest high precision screw rotors for a major gas compression project in the Far East using its EX Series model. The process necessitated the manufacture of 816 mm diameter rotors as matched pairs, with a finished dimensional tolerance between the male and female forms maintained to tens of microns across the intermeshing profile surfaces. On behalf of a major Chinese compressor manufacturer, the company then produced one of the largest helical profile milling machines ever constructed. The machine in question, an 8EX model, is now in daily use, dry pre-machining then finishing outsize screw compressors for the gas processing industry. What made this particular project so remarkable, however, was the sheer scale of the technology involved. Weighing in at an incredible eight tonnes plus, each of the stainless steel rotors produced required a machine capable of handling diameters of up to 850 mm and material lengths of up to 4.5 m. Not surprisingly, the project presented a number of major challenges for which Holroyd called on its well-known and considerable ability to develop ingenious engineering solutions engineering solutions (Ed's note: The full PTG/Holroyd article will be published in the March/April issue of Gear Technology in our Grinding/Abrasives round-up).