Polishing device and polishing method for counterweight casting

The invention relates to the technical field of counterweight part grinding, and discloses a grinding device for counterweight part casting, which comprises a machine table, a concave grinding seat for placing a workpiece is arranged above the machine table, two groups of symmetrical support rods are fixed in the machine table, a plurality of sliding blocks are fixed below the concave grinding seat, and the concave grinding seat and the sliding blocks are fixed on the machine table. A sliding block is arranged on the concave grinding seat and is connected to the supporting rod in a sliding mode, a rack is fixed to one side of the concave grinding seat, and a driving assembly meshed with the rack is fixed to the concave grinding seat; and when a second spring stops accumulating force, the two balance weights can be preliminarily positioned, so that the surfaces of the two sides and the lower surfaces of the two sides of each balance weight and the side face of a protruding part are automatically and specifical