Abstract: The theoretical calculation formulas of the spinning forces for the 3D non-axisymmetrical thin-walled offset tubes based on the slab method are presented. The effects of the circumferential rotational angle γ of the roller, the offset value δ of the blank per path on the changes of the spinning forces are analyzed theoretically. It shows that during the offset tubes spinning, the spinning forces vary periodically along with γ, and the extent of the variation depends on the value of δ. The effects of the main processing parameters, such as the offset value δ of the blank per path，the feed rate f of the roller, and the nominal reductionΔof the blank radius per path, on the spinning forces are analyzed experimentally and theoretically. The calculation results conform well to the experimental ones.

Key words: Offset tubes, Slab method, Spin-forming, Spinning force