Milling machines are one of the most widely used machines in precision metal machining industry. During milling, the work piece which is rigidly held on the table of the milling machine with the help of a milling vice or clamps is fed against a rotating milling cutter which is held in the spindle inside the fixed head of the milling machine. Milling cutter is normally a multi point cutting tool with cutting tooth made out of hard materials like high speed steel or carbide. Furthermore milling machine can also be used for various other metal cutting operations like drilling, tapping, reaming and boring with the help of different attachments and collets.
Milling machines come in various sizes and shapes depending upon the size of the work piece, accuracy required, type of cutters used. The type of metal cutting operations to be performed is another factor. You may want a machine that can be used for drilling and tapping in addition to normal milling operations. Further more you have to consider the complexity of the profile to be milled. Some of the most commonly used milling machines are, small milling machines, vertical milling machines, horizontal milling machines, precision tool room milling machines high speed machining centers and cnc milling machines.
Types of Milling Machines
Let us examine the various types of milling machines and types of milling operations used for metal cutting. Milling machines can be generally classified into Vertical milling machines and horizontal milling machines. Again you have conventional milling machines and cnc milling machines under each of these classifications.
Vertical Milling Machines
Vertical milling machines are one of the most versatile metal cutting machines. In a vertical milling machine the spindle of the machine is vertical to the table on which the work piece is loaded. The milling cutter will be mounted on the spindle which will be rotating inside the vertical head of the machine. The precision tool room milling machines are often equipped with swivel heads. As a result of this, it is possible to perform milling of complex profiles using various cutting tools. The above picture shows a precision tool room milling machine from bridgeport. It falls under the category of vertical milling machines.
Horizontal Milling Machine
On a horizontal milling machine, the axis of the spindle on which the milling cutter is mounted is horizontal to the work table. Usually horizontal milling machines are used to remove surplus amount of material from the work piece. For example milling the the length and width of large steel plates. Face milling cutters like shell end mills and carbide insert milling cutters are commonly used on these types of machines.
CNC Milling Machines
Computer numerically controlled milling machines drastically reduced the machining time. All the three axes (x,y and Z) are accurately controlled by the servo motors. Thus producing high precision machined parts with less efforts. Most of all, complex 3D profiles can be milled to very high accuracy and surface finish. As a result the time taken to do the finishing operations are considerably reduced.