Protection assembly and numerical control plane milling and grinding machine

The protection assembly comprises a device main body, the device main body is of a hollow open box body structure, a placing disc and a grinding disc are arranged in the device main body, a fixing block is fixed to one side of an opening of the device main body, a sliding groove and a sliding stop groove are formed in the fixing block, a baffle is arranged in the sliding groove, and the baffle is arranged in the sliding stop groove. Sliding blocks are arranged on the two sides of the baffle, racks and rollers are arranged on the sliding blocks, and non-return blocks are connected to the racks; the device has the advantages that the fixing plate is conveniently and rapidly installed on the device body through the bolt, the baffle can be lifted by pulling the handle, the baffle is prevented from falling under the action of the non-return block, the baffle can fall by pulling the handle to drive the non-return block to move, and a machined workpiece can be conveniently placed in and taken out through the operati