A. Precision of seamless steel pipe outer diameter: it depends on the order (reduction) diameter method, the working condition of the equipment, technological system, etc.

Permissible deviation of outside diameter: δ=(D-Di)/Di ×100% D: maximum or minimum mm

Di: nominal outer diameter mm

B. The wall thickness precision of steel tube: it is related with pipe billet heating quality, process design and adjusting parameters of each deformation process and tool quality and the quality of lubrication and so on.

Allowable deviation of wall thickness: ρ=(S-Si)/Si×100% S: maximum or minimum wall thickness on the cross section

Si: nominal wall thickness mm

C. Ovality of steel pipe: it means the degree of out of round steel tube.

D. Length of steel tube: normal length, fixed (multiple) length, length of allowable deviation

E. Bending of steel tube: it indicates steel radial degrees: length of per meter steel tube bending, bending of the compete steel tube length

F. Transverse cutting slope of steel pipe: steel pipe end face and the level of tilt of the pipe cross section.

G. Steel pipe transverse groove angle and the blunt edge.