Hot Gas Generators Vertical Mill Internals A vertical mill takes its name after the vertical axis upon which it rotates. The operating parameters of vertical mills are seldom altered once optimum productivity is established. Developments in metallurgy of the grinding element can help achieve efficiency improvements, resulting in cost savings. The most important internals in a vertical mill are the rollers and tables (also called vertical mill tires and rings respectively). Several rollers, depending on the size of the mill, are placed around the table. The material to be ground is fed into the mill from its top. It falls on the table placed at the bottom of the mill.