04.1 · CNC Milling Machines
CNC Milling Fundamentals
In milling, the tool rotates and the workpiece stays still on the table. This is the opposite of a lathe. Milling machines make prismatic parts — blocks, plates, housings, molds — by cutting pockets, faces, holes, and profiles.
Vertical vs Horizontal Milling
| Vertical Mill / VMC | Horizontal Mill / HMC | |
|---|---|---|
| Spindle direction | Downward onto table | Sideways onto a tombstone/fixture |
| Chip evacuation | Chips fall on the part | Chips fall away |
| Workholding | Vise, plate, simple fixture | Tombstone, pallet, 4-sided fixture |
| Best for | Molds, plates, one-sided work, prototyping | Production, boxy parts, multi-sided machining |
Axis Configurations
| Axes | What you can do |
|---|---|
| 3-axis (X/Y/Z) | Move table left-right, front-back, spindle up-down. Mill top face, holes, pockets, 2.5D contours. |
| 4-axis (+ rotary table) | Part rotates so you can machine sides without re-fixturing. Indexing or continuous. |
| 5-axis (+ second rotary) | Tool tilts relative to part. Complex 3D surfaces, multi-angle access in one setup. |
Key Milling Operations
| Operation | What it does |
|---|---|
| Face milling | Square up a surface with a face mill |
| End milling | Cut slots, pockets, profiles |
| Drilling / tapping | Create holes, threads (often on the same machine) |
| Boring | Accurately size an existing hole |
| Pocketing / profiling | 2D and 3D cavity and contour work |
Milling vs drilling on a mill: Any CNC mill can drill, tap, and bore. The difference between a basic mill and a machining center is the automatic tool changer (ATC) and the ability to run unattended cycles. See Machine Components and VMC vs HMC.