Abstract: The paper describes the O.D. and wall-thickness tolerances and internal/external surface quality of midium and heavy wall steel pipes produced in Hengyang Steel Pipe Factory by means of φ108mm three-roll mill complete with a 12-stand slight-stretch reducing mill. The practice proves it very successful to produce such pipes by applying proper reducing process and using a slight-stretch reducing mill instead of two-roll reducing mill plus rotary sizing mill.