Machining
CNC Milling vs CNC Turning
Milling spins the tool against a fixed part for prismatic shapes; turning spins the part against a fixed tool for round parts. Part geometry decides the process, and many parts need both.
| CNC Milling | CNC Turning | |
|---|---|---|
| Motion | Rotating tool, fixed part | Rotating part, fixed tool |
| Best geometry | Prismatic, pockets, slots, faces | Cylindrical, shafts, bores |
| Axes | 3 to 5 axis | 2 axis, plus live tooling |
| Round parts | Slower, less accurate roundness | Fast, excellent roundness |
| Off-axis features | Native | Needs live tooling or a second op |
| Typical throughput | Depends on toolpaths | High on round stock |
| Setup | Fixturing prismatic stock | Chuck or collet on bar stock |
Choose CNC Milling when
- Prismatic parts with pockets, faces, and holes
- Complex 3D surfaces or multi-face features
- Non-cylindrical geometry
Choose CNC Turning when
- Round parts like shafts, pins, and bushings
- High roundness and concentricity requirements
- Producing many turned parts from bar stock
The verdict
Turn round parts and mill prismatic ones. Parts with both round and prismatic features often run on a mill-turn machine or move between a lathe and a mill in sequence.
Cost comparison
Turned parts from bar stock usually cost less than milled equivalents because a lathe holds the part once, runs unattended with a bar feeder, and cuts continuously. A bushing turned in 90 seconds might take 6 minutes across two milling setups. Price rises fastest when a round part carries off-axis features, which is the signal to quote a live-tooling lathe or mill-turn.
Common questions
What is the difference between CNC milling and turning?
In milling the tool rotates and the part is fixed, which suits prismatic shapes. In turning the part rotates and the tool is fixed, which suits round parts like shafts and bores.