Grinder

The utility model discloses a grinder which is provided with a rotating cylinder. The cylinder body of the rotating cylinder is provided with an aligning slice in V-shaped, the side edges of the cylinder body are respectively provided with a fixed positioning slice and a rotatable rotary cover, and the side edges are also provided with a conduct pipe used to arrange a metal piece. The bottom of the conduct pipe is provided with a guide slot and a sloping plate used for metal objects to slide out, the positive and negative rotation of the rotating cylinder can be driven by a transmission device to realize the grinding of the metal piece and the sliding out of the metal piece respectively. The grinder is suitable for the grinding of a large amount of metal pieces, and feeding and fetching materials manually are not required.