Basic Machining Operations

What is Basic Machining Operations?

Machining operations involve removing material from a workpiece to achieve specific contours or dimensions using one or more cutting tools. Various operations, such as milling, turning, drilling, boring, and grinding, are commonly used to remove metal through shearing processes. There are two types of basic machining operations: Turning and Milling. In a turning operation, the workpiece is clamped with spindles and rotates at a high speed, while a fixed cutting tool removes material from it through a shearing process. On the other hand, milling operations involve a rotating cutting tool that is always clamped with the spindle and spins at a higher speed. The workpiece is mounted on a machine bed, and excess material is removed through the shearing process. In Turning, the cutting tool is fixed and the workpiece rotates, whereas, in Milling, the cutting tool rotates while the workpiece remains stationary. The following pictures illustrate these two basic machining operations: Turning and Milling.

Milling - In milling, a multi-edge cutting tool rotates at high speed while a stationary workpiece removes excess material through shearing. Various milling operations, such as up milling, side milling, and straddle milling, are used for different machining processes. 

Types of milling operation

Milling operations can be categorized into two groups: Peripheral milling and Face milling. In peripheral milling, the milling cutter's surface is parallel to the machining surface of the workpiece, with cutting edges present on the outer surface. Face milling, on the other hand, involves cutting edges on both the rim and outer surface of the cutter, which is positioned perpendicular to the cutting surface of the workpiece.

 

Peripheral Milling - Peripheral milling includes operations such as slab milling, side milling, straddle milling, and slotting, where the cutter is arranged parallel to the workpiece, and the cutting edges are present only on the outer surface. The following pictures depict different peripheral milling operations.

In peripheral milling operations, the relative movement direction of the workpiece with the cutter can occur in two ways: Conventional milling or Up milling, and Climb milling or Down milling. Conventional milling involves the feed direction of the cutting tool being opposite to its rotation, while in climb milling, the cutting tool feeds in the same direction as its rotation. Hence, the key difference between up milling and down milling is the direction of the cutter's rotation relative to the path of travel. The following picture illustrates these two different types of peripheral milling operations. 

Face milling - In face milling, the cutter is arranged perpendicular to the workpiece. This process involves cutting edges present in both the cutter face and outer surface. Various operations, such as conventional face milling, partial face milling, end milling, profile milling, pocket milling, and surface contouring, fall under the category of face milling. The following pictures explain different face milling operations.

 

Turning – This simple machining process, also known as lathe operation, involves rotating the workpiece at a high speed while a stationary cutting tool removes material through shearing. Typically, cylindrical workpieces are created using this machining operation.

 

Types of Turning Operations

Different types of turning operations are performed, including simple turning, facing, boring, drilling, parting, threading, knurling, etc. Turning operations typically produce straight, tapered, and grooved cylindrical workpieces. These operations can be classified into four primary categories: straight turning, taper turning, contour or profile turning, and form tool turning. The following pictures illustrate different turning operations commonly found with CNC lathes or turning machines.

Boring - Boring is similar to turning, except it involves removing material from the internal diameter of the workpiece. A single-point cutting tool is often used to enlarge a drill hole in the boring operation.

Drilling - This operation creates different types of holes in a workpiece. There are various drilling operations, including plain drill, step drill, counter shank, and counterboring.

Grinding - Grinding is a finishing machining operation where a grinding wheel is used to remove a very small amount of material from the surface area of the workpiece. The grinding wheel rotates at high speed while the workpiece moves slowly, resulting in material removal through shearing from the exterior.