Abstract: Briefed are the difinition and effect of the deformable body external end, and several cases concerning application of the rolled-piece external end-increasing method to reduce uneven metal deformation.The principle and effect of billet tail-end centering operation as used during seamless steel tube manufacturing process are explained with the external end theory.The author here presents the idea of using the semi-non-crop and non-crop rolling process to roll seamless steel pipes with the stretch reducing mill, and also analyzes the problems as probably encountered with during such rolling process.