Metal piece polishing device

The utility model relates to the technical field of metal processing, in particular to a metal piece polishing device which comprises a working table, a polishing box is arranged above the working table, a polishing disc is arranged at the top of the polishing box, a clamping part used for fixing a metal piece to be polished is arranged in the polishing box, and the outer side of the clamping part is connected with an overturning assembly used for overturning the clamping part. The overturning assembly comprises fixed cavities fixed to the left side wall and the right side wall of the grinding box, a driving motor penetrating into the fixed cavities is arranged on the outer side wall of the grinding box, a rotating gear disc is arranged at the output end of the driving motor, an elliptical gear disc meshed with the rotating gear disc is arranged above the rotating gear disc, and double rotating rods which are horizontally arranged are arranged on the inner side of the elliptical gear disc. The tail ends of th