Open impellers are commonly machined on vertical mills because the open vane design allows direct tool access. The impeller is mounted upright on a rotary table so it can rotate smoothly while the cutter approaches from above. This setup makes it possible to shape complex curved vanes without enclosing shrouds getting in the way. As the rotary table turns, the milling cutter removes material in controlled passes, gradually forming each vane profile. Ball nose or form cutters are often used to ac