15 Milling Operation Types & Working Explained [PDF]

What is the Definition of Milling Operation?

Milling is a famous machining technique in which a rotating cutter removes material from a workpiece systematically to give it a desired shape.

It employs rotary cutting tools with multiple edges to precisely shape and refine the workpiece, creating diverse shapes and dimensions. This process is crucial in manufacturing, transforming raw materials into intricate components across various industries.

Modern milling machines often utilize Computer Numerical Control (CNC) for automated precision control throughout the operation.

Operations Performed on Milling Machines

Following are the different types of Milling Machine Operations:

  1. Gear Milling
  2. Helical Milling
  3. Cam Milling
  4. Thread Milling
  5. Plain Milling Operation
  6. Face Milling Operation
  7. Side Milling Operation
  8. Straddle Milling Operation
  9. Angular Milling Operation
  10. Gang Milling Operation
  11. Form Milling Operation
  12. Profile Milling Operation
  13. End Milling Operation
  14. Saw Milling Operation
  15. Milling Keyways, Grooves, and Slot

#1 Gear Milling

Gear Milling

Gear cutting on a milling machine utilizes a form-relieved cutter, which can be cylindrical or end mill type. This cutter’s profile precisely matches the gear tooth space. To create equally spaced gear teeth on a gear blank, the workpiece is secured on a universal diving head and indexed accordingly.

#2 Helical Milling

Helical Milling

Helical milling is used to make helical flutes or grooves along the outer surface of a cylindrical or conical workpiece. This is done by rotating the table to the desired helix angle. The workpiece is then feeded against the rotary cutting edges of a milling cutter. Helical milling finds applications in producing helical gears, cutting helical grooves or flutes on drill blanks, or reamers.

#3 Cam Milling

Cam milling involves crafting cams using a milling machine equipped with a universal dividing head and a vertical milling attachment. The cam blank is affixed to the end of the dividing head spindle, while an end mill is held in the vertical milling attachment. Maintaining parallel alignment between the cam blank axis and the end mill spindle is crucial during setup.

The dividing head is synchronized with the table feed screw, enabling the cam to rotate about its axis while being fed against the end mill. By adjusting the cam’s axis within a range of 0 to 90 degrees relative to the table surface, different cam rise configurations can be achieved.

#4 Thread Milling

Thread milling operations has single or multiple thread milling cutters to make threads accurately. This operation has three driving motions within the machine: one for the cutter, one for the workpiece, and one for the longitudinal movement of the cutter.

In the case of a single thread milling cutter, the cutter head is swiveled to match the exact helix angle of the thread. As the cutter rotates on the spindle, the workpiece revolves slowly about its axis. The thread is completed in a single cut by setting the cutter to the full depth of the thread and feeding it along the entire length of the workpiece.

When multiple thread milling cutters are employed, the cutter axis and work spindle are aligned parallel after adjusting the depth of cut to match the full depth of the thread. The thread is completed by feeding the rotating cutter longitudinally through a distance equal to the pitch length of the thread while the workpiece undergoes one complete revolution.

#5 Plain Milling

Plain milling is also called as slab milling. It is a typical milling machine operation which is used to create a flat, horizontal surface by aligning it with the rotation axis of the cutter. In this the workpiece and cutter is secured on the machine by adjusting the depth of cut using the vertical feed screw. Then the machine is started with appropriate speed and feed settings.

#6 Face Milling Operation

Face Milling Operation

Face milling represents one of the most straightforward milling machine operations. In this process, a face milling cutter revolves around an axis perpendicular to the work surface.

The operation is typically executed using plain milling techniques, with the cutter securely mounted on a stub arbor. Its purpose? To create a precisely flat surface. The depth of cut is meticulously adjusted by rotating the crossfeed screw of the table.

#7 Side Milling Operation

Side milling involves the production of a flat vertical surface on the side of a workpiece using a specialized side milling cutter. The depth of cut is meticulously controlled by rotating the vertical feed screw of the table.

#8 Straddle Milling Operation

Straddle Milling Operation

Straddle milling involves creating flat vertical surfaces on both sides of a workpiece using two side milling cutters mounted on the same arbor. The spacing between the two cutters is adjusted with suitable spacing collars. This method is often employed to machine square or hexagonal surfaces.

#9 Angular Milling Operation

Angular Milling Operation

Angular milling involves creating an angled surface on a workpiece. This angle is not perpendicular to the axis of the milling machine spindle. The resulting angular groove can be a single or double angle and may vary in included angles depending on the type and contour of the angular cutter utilized. An elementary application of angular milling is crafting V-blocks.

#10 Gang Milling Operation

Gang Milling Operation

Gang milling involves machining multiple surfaces of a workpiece simultaneously by feeding the table against several cutters mounted on the machine’s arbor, each with either the same or different diameters. This method significantly reduces machining time and is commonly employed in repetitive tasks. The cutting speed for a gang of cutters is determined by the cutter with the largest diameter.

#11 Form Milling Operation

Form Milling Operation

Form milling is the process of creating an irregular contour utilizing form cutters, resulting in shapes such as convex, concave, or other variations. Post-machining, the formed surface undergoes inspection using a template gauge to ensure precision and accuracy. Notably, the cutting rate for form milling typically ranges from 20% to 30% lower compared to plain milling operations.

#12 Profile Milling Operation

Profile Milling Operation

Profile milling entails replicating the outline of a template or intricate shape from master dies onto a workpiece. This process employs various cutters specifically designed for profile milling tasks. Among these, the end mill stands out as a commonly utilized milling cutter in profile milling operations.

#13 End Milling Operation

End Milling Operation

End milling involves generating a flat surface on a workpiece, which can be oriented vertically, horizontally, or at an angle relative to the table surface. This operation employs an end mill cutter designed for this purpose. Additionally, end milling cutters find application in creating slots, grooves, or keyways on workpieces. Vertical milling machines are particularly well-suited for end milling tasks due to their configuration and capabilities.

#14 Saw Milling Operation

Saw Milling Operation

Saw-milling involves creation of narrow slots or grooves on a workpiece by using a specialized saw-milling cutter. This operation can also be employed for complete parting-off tasks. During saw-milling, the cutter and workpiece are positioned such that the cutter aligns directly over one of the T-slots on the table, ensuring precise and controlled cutting action.

#15 Milling Keyways, Grooves, and Slot

Milling Keyways, Grooves, and Slot

Within milling machines, the intricate task of shaping keyways, grooves, and slots of diverse configurations and dimensions is feasible. This is achieved through the utilization of a spectrum of cutting implements including plain milling cutters, metal slitting saws, end mills, and side milling cutters. Open slots are adeptly crafted employing plain milling cutters, metal slitting saws, or side milling cutters, while closed slots are conventionally fashioned using end mills.


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