What are turning and milling? What are the differences? What are the advantages of turning and milling compound

In the field of mechanical processing, turning and milling are two of the most fundamental and widely used cutting methods. The core differences between the two stem from the essential differences in processing principles, motion forms, and applicable scenarios. Specifically, they can be distinguished in detail from the following six key dimensions:

I. Core Processing Principle: The essential difference between "who moves and who doesn't"

This is the most fundamental difference between turning and milling, which directly determines the processing logic of both:

Turning: The workpiece rotates while the tool remains fixed (or only linear feed is performed). During processing, the workpiece is clamped on the machine tool spindle and rotates at high speed with the spindle (this is the "main motion", providing cutting power). The turning tool is fixed on the tool rest and only moves slowly in a straight line along the axis or radial direction of the workpiece (this is the "feed motion", which controls the cutting amount). Through the cutting edge of the tool, the excess material on the surface of the workpiece is "turned off", forming a rotary surface. Analogy: Similar to "peeling an apple", the apple (workpiece) rotates while the fruit knife (turning knife) remains stationary or moves slowly to peel out a round apple skin.

Milling: The cutting tool rotates while the workpiece remains stationary (or undergoes feed motion). During processing, the milling cutter (multi-edge tool) is clamped on the machine tool spindle and rotates at high speed with the spindle (main motion). The workpiece is clamped on the worktable and moves in a straight line or curve (feed motion) along the X/Y/Z axis with the worktable. The workpiece is alternately cut through multiple cutting edges of the milling cutter, forming non-rotary surfaces such as planes, grooves, and complex contours. Analogy: Similar to "grinding a table with a grinding wheel", the grinding wheel (milling cutter) rotates, and the table (workpiece) moves slowly to grind a smooth surface.

Ⅱ. Applicable Processing Objects: "Rotating Bodies" vs. "Non-rotating Bodies"

The processing principles of the two determine that there are significant differences in the shapes of the parts they are applicable to:

Turning: Rotating body parts (i.e., the contour shape of the part remains unchanged after rotating around a certain axis) are often cylindrical bars, such as shafts (such as motor shafts, step shafts), discs (such as flange discs, gear blanks), sleeves (such as bearing sleeves, hydraulic cylinder barrels), and threads (such as bolts, nuts).

Milling: Non-rotating body parts (or non-rotating features on rotating bodies), workpieces are often rectangular or irregular-shaped parts, such as box types (such as gearbox housings), support types (such as machine tool supports), planes (such as steel plate surfaces), grooves (such as V-shaped grooves, T-shaped grooves), and complex profiles (such as mold cavities, turbine blades)

Ⅲ. Tool Structure: "Single-edge Simple" vs. "Multi-Edge Complex"

The structural differences of cutting tools directly correspond to processing efficiency and applicable scenarios:

Turning tools: They have a simple structure and are mostly single-edge tools (a few special turning tools are multi-edge, such as forming turning tools). The shape of the cutting edge of the tool is designed according to the processing requirements (such as cylindrical turning tools, internal hole turning tools, cutting tools, thread turning tools). Features: Easy to manufacture and grind, with relatively low cost; However, single-edge cutting involves only one cutting edge working at a time, resulting in relatively low processing efficiency (suitable for continuous cutting of rotary surfaces).

Milling cutters: They have complex structures and are mostly multi-edge tools (with the number of edges ranging from 2 to dozens). Common types include:

End mills: used for machining flat surfaces and step surfaces;

End mills: used for processing grooves, sides, and complex contours;

Three-edge milling cutter: used for machining right-angle grooves;

Forming milling cutter: Used for processing contours of specific shapes (such as gear tooth grooves).

Features: Multi-edge alternating cutting, high cutting efficiency (especially in high-speed milling); However, the manufacturing precision requirements for cutting tools are high and the cost is relatively high.