Types of Milling Operations
Various types of milling operations cater to diverse machining needs. Face milling creates flat surfaces, while end milling produces slots and pockets.
The various types of Milling operations include:
Plain or Slab Milling:
Fig 1: Plain Milling
Plain milling entails the creation of a flat horizontal surface parallel to the cutter's axis using a plain milling cutter.
Face Milling:
Fig 2: Face Milling
Face milling involves producing a flat surface perpendicular to the cutter's axis.
Angular or Bevel Milling:
Fig 3: Angular Milling
Angular or bevel milling machines have flat surfaces at angles different from the cutter's rotation axis, utilising single or double angle cutters as needed.
Straddle Milling:
Fig 4: Straddle milling
Straddle milling is the process of creating two vertical flat surfaces on both sides of the workpiece using two side milling cutters separated by collars, commonly applied for milling square and hexagonal shapes.
Gang Milling:
Fig 5: Gang Milling
Gang milling achieves multiple surface operations simultaneously by feeding the table against multiple cutters with opposing helical teeth, optimising machining time and efficiency, particularly in mass production.
Form Milling:
Form milling produces irregular surfaces or contours using specialised form cutters, accommodating convex, concave, or custom shapes.
End Milling:
Fig 6: End Milling
End milling concurrently generates peripheral and face milling operations, creating vertical, horizontal, or angled surfaces and is useful for slotting, grooving, and keyway milling.
T-Slot Milling:
Fig 7: T Slot Operation
T-slot milling occurs in stages, initially using an end milling cutter for plain slots, and subsequently, a T-slot cutter enlarges the slot and mills its bottom face.
Gear Milling:
Fig 8: Gear Milling
Gear milling involves shaping various gear types on a milling machine using form relieved cutters that match the gear tooth profiles, typically done with equally spaced gear teeth and a universal dividing head for indexing.
Saw Milling
Fig 9: Saw milling
Sawmilling employs a generously sized cutter with a slender profile, designed for precision machining of narrow slots or the division of a workpiece into two segments. To prevent undesirable heat and stress buildup that can lead to tool and workpiece damage, the feed rate and spindle speeds are intentionally maintained at a lower pace compared to other milling processes. Typically, this operation is carried out on horizontal milling machines.
Side Milling
Fig 10: Side Milling Cutter
Side milling is the preferred choice when you need to machine a flat vertical surface onto your workpiece. In this process, a side milling cutter is affixed to the arbour of a horizontal milling machine, and the workpiece-holding table is elevated to the desired depth of cut before being fed into the cutter. Additionally, the cutter is equipped with helical flutes to facilitate chip evacuation during machining, and its diameter is typically smaller than the width of the workpiece, similar to that of a drill bit.
Thread Milling
Fig 11: Thread Milling
Thread milling is a machining process used to create threads within a pre-existing hole in a workpiece, employing specialised tools known as thread mills. This operation is compatible with both vertical and horizontal milling machines. Unlike tapping, thread milling is particularly well-suited for generating threads in holes larger than the diameter of the milling tool. Thread milling entails three distinct movements: one for rotating the thread mill, another for its axial movement into and out of the hole, and a third for advancing the workpiece to facilitate the cutting of the desired threads.
Cam Milling
Cam milling is a specialised machining technique primarily employed in the fabrication of cams. This method utilises a universal indexing head to both rotate and position the workpiece, allowing the cutting tool to remove material and achieve the desired cam shape. The cam axis can be adjusted within a range of 0 to 90 degrees to achieve the desired cam profile.
