In previous studies, it has been proved that the process of interior magnetic abrasive finishing using a magnetic machining tool is effective in improving the shape accuracy (roundness) of thick SUS304 stainless steel tube. But the mechanism of the improvement is undefined. In this paper, mainly discussing the improvement of interior roundness of the thick SUS304 stainless steel tube by dynamic and trajectory analysis. In particular, the factors affecting the improvement of interior roundness of the thick tube was studied by discussing the reciprocating velocity of magnetic pole unit. Firstly, the force analysis diagram of the magnetic machining tool in the model doing uniform rotational motion was performed. Secondly, according to the dynamics, dynamic equation of the magnetic machining tool was discussed. And then, the motion model of trajectory of the magnetic machining tool was discussed. Finally, the three reciprocating velocities of magnetic pole unit were compared in the experiments. The results correspond to the discussion that lower reciprocating velocity of magnetic pole unit is beneficial to the improvement of interior roundness.
