The basic principle for groove spinning forming is metal volume transfering, which conforms to the law of plastic deformation volume invariance; in other words, the groove forming is realized by the material flowing on the wall of tube or the increase or decrease of wall thickness, as the change of wall thickness should belong to the category of flow forming. The difference is that the general flow forming material produces axial flow, and the pressure of this groove spinning forming also produces radial flow of material.