CNC Milling
CNC milling removes material with a rotating cutter moving under computer control to produce flat faces, pockets, slots, holes and 2D or 3D profiles. It is used for plates, blocks, housings, brackets and any component with features that are not simply round.
What it is
The workpiece is clamped to the machine table while an end mill, face mill or drill spins and moves along programmed paths in X, Y and Z. Features are cut layer by layer to the drawing dimensions.
Milling handles everything from simple drilled and tapped plates to complex contoured surfaces. Vertical machining centres (VMCs) are the most common type of CNC milling machine for this work.
Typical applications
- Mounting plates and base plates
- Housings, covers and manifolds
- Brackets, clamps and fixtures
- Moulds, dies and tooling inserts
- Slotted, pocketed and profiled parts
Suitable materials
- Aluminium alloys
- Mild steel and alloy steels
- Stainless steel
- Tool steels (pre-hardened or annealed)
- Brass and engineering plastics
Points to consider
- Internal pocket corners always have a radius equal to at least the cutter radius; design radii rather than sharp internal corners.
- Deep, narrow pockets (depth over about 4× cutter diameter) are slow and costly; keep them shallower where possible.
- Use standard hole and thread sizes so standard drills and taps can be used.
- Features on several faces need more setups; group them on as few faces as possible.
Frequently asked questions
What files do you need for CNC milling?
A PDF drawing with dimensions and tolerances is essential. For 3D shapes or complex contours, a STEP or IGES model speeds up programming.
Can CNC milling produce 3D shapes?
Yes. With 3-axis milling and ball-nose cutters, curved and contoured surfaces are routine. Undercuts and features on many angles may need 4- or 5-axis machining.
Why are internal corners rounded on milled parts?
Milling cutters are round, so internal corners take the cutter's radius. If a sharp corner is essential, EDM or a relief cut can be used.