What is CNC milling?
CNC milling uses rotating cutting tools to remove material from a stationary workpiece. The tool moves in multiple axes to create complex shapes, slots, holes, and surfaces.
- Motion — rotating tool, stationary workpiece
- Applications — complex surfaces, pockets, holes, slots, 3D contours
- Typical parts — housings, brackets, molds, enclosures
- Axis configurations — 3-axis, 4-axis, 5-axis
5-axis milling can machine complex geometries in a single setup, reducing handling time and improving accuracy.
What is CNC turning?
CNC turning uses a stationary cutting tool against a rotating workpiece. The workpiece spins while the tool removes material to create cylindrical shapes.
- Motion — rotating workpiece, stationary tool
- Applications — cylindrical surfaces, shafts, threads, tapers
- Typical parts — shafts, pins, bushings, connectors
- Variations — Swiss turning, multi-axis turning
For parts with both cylindrical and flat features, consider mill-turn machines that combine both processes in one setup.
Key differences
| Factor | CNC Milling | CNC Turning |
|---|---|---|
| Motion | Tool rotates, workpiece stationary | Workpiece rotates, tool stationary |
| Primary geometry | Prismatic, 3D surfaces | Cylindrical, rotational |
| Typical parts | Housings, brackets, enclosures | Shafts, pins, bushings |
| Tooling | Multiple tool types and sizes | Single-point tools |
| Material removal | Point-to-point cutting | Continuous cutting |
| Setup time | Longer (multiple tools) | Shorter (single tool) |
Choosing milling for parts that could be more efficiently turned. For cylindrical parts with simple features, turning is typically faster and more cost-effective.
When to choose milling
- Parts with complex 3D surfaces or contours
- Parts requiring pockets, slots, or multiple hole patterns
- Components with flat surfaces and right-angle features
- Parts that require machining on multiple faces
When to choose turning
- Cylindrical or round parts
- Shafts, pins, and connectors
- Parts requiring concentric features
- High-volume production of rotational parts
Many parts can be manufactured using either process. The best choice depends on the specific geometry and functional requirements of the part.
Cost considerations
- Milling — typically higher machine cost per hour, but suitable for complex parts
- Turning — generally lower cost for cylindrical parts, faster cycle times
- Combined processes — some parts require both milling and turning
Frequently Asked Questions
What is the main difference between milling and turning?
In milling, the tool rotates and the workpiece is stationary. In turning, the workpiece rotates and the tool is stationary.
Which process is more expensive?
Milling is generally more expensive per hour due to more complex tooling and multiple setups. Turning is typically more cost-effective for cylindrical parts.
Can a part be both milled and turned?
Yes. Many parts require both processes. Mill-turn machines can perform both operations in a single setup.
How do I choose between milling and turning?
Choose turning for cylindrical parts, milling for complex shapes and flat surfaces. If your part has both characteristics, consult your supplier.