Polishing device for needle cylinder of circular knitting machine

The invention belongs to the technical field of grinding, and particularly relates to a grinding device for a needle cylinder of a circular knitting machine, which comprises a machine body and a grinding wheel, a pneumatic chuck connected with the grinding wheel is arranged on the machine body, a cover is arranged on the outer side of the grinding wheel on the machine body, and a releasing assembly comprises a pressing piece in sliding connection with the cover. The cover is provided with a first switch for controlling the pneumatic chuck to be loosened, and a standby grinding wheel is arranged on the side face of the machine body and located on the horizontal position of the pneumatic chuck. And when the pressing piece moves downwards, a switch of the electromagnet can be turned on at the same time to enable the electromagnet to be powered on, so that when the pressing piece is embedded into the clamping groove with magnetic force, the pressing piece can be attracted to the grinding wheel, and after the pneu