Cast blanks with large-scale free form surfaces are very difficult to manufacture because of significant casting distortions. It is concerned that the development and application of a hogging algorithm for preparing the blanks for an extended rough cutting. The procedure includes three main phases. They are the reconstruction of the free form surface with scattered points based on a special Hermite’s interpolation, intersection of curved surfaces to define the hogging areas, and the tool path planning. The result shows that the algorithm is greatly valid in reducing the invalid tool paths so that the work efficiency can be improved remarkably. It is concerned that the development and application of a hogging algorithm for preparing the blanks for an extended rough cutting. The procedure includes three main phases. They include: blanks with large-scale free form surfaces are very difficult to manufacture because of significant proposition distortions. are the reconstruction of the free form surface with scattered points based on a special Hermite’s interpolation, intersection of curved surfaces to define the hogging areas, and the tool path planning. The result shows that the algorithm is greatly valid in reducing the invalid tool paths so that the work efficiency can be improved remarkably.