MACHINING Copyright Goodheart-Willcox Co., Inc. Chapter 26 Milling Machines 443 Plain Milling Machines The cutter spindle projects horizontally from the col- umn on the plain milling machine, Figure 26-4. For this reason, plain milling machines are often referred to as horizontal milling machines. The worktable has vertical, traverse, and longitudinal movement. Universal Milling Machines The universal milling machine is similar to the plain milling machine, but the table has a fourth axis of movement. On this type of machine, the table can be swiveled on the saddle through an angle of 45° or more. This makes it possible to produce spiral gears, spiral splines, and similar work, Figure 26-5. in vertical movement (Z axis). The knee supports the worktable and contains the mechanism for obtaining table movement. The table movements are traverse (Y axis) and longitudinal (X axis). See Figure 26-3A. The three basic types of column-and-knee milling machines are plain (horizontal spindle), universal (horizontal spindle), and vertical spindle. The orienta- tion of the X, Y, and Z axes is different on a horizontal column-and-knee milling machine, Figure 26-3B. Sharp Industries, Inc. Figure 26-4. A plain horizontal milling machine. WMW Machinery Company, Inc. Figure 26-3. Column-and-knee milling machines. A—Vertical. B—Horizontal. A B Knee X Y Z Knee n Column X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Y Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z WMW Machinery Company, Inc. Figure 26-5. The table on a universal milling machine can be swiveled at an angle to the cutting tool. This feature makes it possible to machine a helical fluted workpiece.