When material enters the mill through the feed pipe from the feeder, and the slurry level inside the cylinder is higher than the lowest generatrix level of the discharge pipe’s inner diameter, the ground material can be discharged from the mill through the discharge pipe. In this type of mill, the end of the discharge pipe inside the hollow shaft journal of the discharge end cover is made into a trumpet shape during manufacturing. A ring-shaped retaining ring is usually installed at the root of the hollow shaft to prevent slurry leaking from the end cover bolt holes from flowing into the bearing. Simultaneously, a spiral is cast into the discharge pipe, with the spiral direction opposite to the mill’s rotation, thus preventing steel balls and ore from being discharged with the slurry. However, this type of mill has a relatively low unit volume production capacity and is prone to over-grinding. Due to its relatively long grinding time, the ore can be ground more thoroughly inside the mill, and the residence time is also longer, resulting in a finer particle size of the ground product. Therefore, this type of mill is usually used for stage grinding and is suitable for concentrate regrinding operations to obtain a finer, qualified product.