Abstract: A mass centering method and apparatus for ascertaining and marking the location of the axis of inertia of rough or premachined rotating article, allowing the marked axis to be used as a centerline in further processing in order to keep the remaining unbalance in the finished article as low as possible. The location of the axis of inertia is determined by an ordinary balancing method, and is then positioned relative to a center marking point, such as the centerline of a center drill, by only two revolving movements: one being a rotation of the article about its own axis of rotation, and the other being an eccentric rotation of the article about the axis of a supporting fixture. An appropriate combination of angle settings for both revolving movements allows the system to locate a theoretically unlimited number of marking points within a circular range of a predetermined diameter.