Conventional Knee Mill Machines / Vertical Knee Mills "Willis Machinery" offers five different models of vertical knee mills, both conventional and CNC Our mill machines range from the model WM3VS, 3 horsepower (3HP) variable speed, R8 spindle mill machine with a 9 inch x 49 inch table, to a massive 5 horsepower (5HP), 40 taper spindle, Series II style machine with a 12 inch x 59 inch ...