3-axis, 4-axis or 5-axis machining: how to choose
More axes are not automatically better. The right choice depends on how many sides of the part need machining and how features relate to each other.
Key takeaways
- 3-axis: lowest cost for flat and prismatic parts.
- 4-axis: features around one axis without re-clamping.
- 3+2: angled features on housings in one setup; often the economical 5-axis option.
- Simultaneous 5-axis: freeform surfaces, undercuts, deep features with short tools.
- Fewer setups, not more axes, is where the accuracy comes from.
The difference in one table
| 3-axis | 4-axis | 3+2 (positional 5-axis) | Simultaneous 5-axis | |
|---|---|---|---|---|
| Axes | X, Y, Z | X, Y, Z + one rotary (A) | Two rotary axes index, then lock | All five move together |
| Sides per setup | One | Around one axis | Up to five | Up to five, plus freeform |
| Typical parts | Plates, simple prismatic parts | Shaft features, parts with holes around a circumference | Housings with angled holes and faces | Impellers, blended and freeform surfaces |
| Relative hourly cost | Lowest | Low | Higher | Highest |
| Setups for a multi-sided part | Several | Fewer | Often one | Often one |
When 3-axis is the right answer
Flat and prismatic parts whose features all face one direction, or two opposite directions with one flip. A 3-axis centre has the lowest hourly rate and the simplest fixturing. On high-volume plates, a dedicated drilling and tapping centre can be faster still.
When to move to 4-axis
When features sit around a part — holes on a circumference, flats on a shaft, several faces of a long part. A rotary A axis indexes the part between operations without re-clamping, which removes a tolerance stack between those features.
3+2 or simultaneous 5-axis?
3+2 tilts and rotates the part into position, locks the rotary axes and machines like a 3-axis machine. It covers most housings with angled holes and faces, and it is often the more economical choice.
Simultaneous 5-axis moves all axes during the cut. It is needed for freeform and blended surfaces, undercuts and impeller-type geometry, and it lets short, rigid tools reach deep features. See our 5-axis machining capacity.
Accuracy: why fewer setups matter more than more axes
The biggest accuracy gain from 4- and 5-axis machining is not the machine itself but the setups it removes. Each re-clamp adds positioning error between features. Machining related features in one setup keeps them in one coordinate system — which is what position tolerances measure.
Our machines
We run 6 three-axis, 3 four-axis and 7 five-axis machining centres (all simultaneous) and route each part to the cheapest machine that holds the drawing. See the machine park.
Frequently asked questions
Is 5-axis machining always more accurate?
Not by itself. It is more accurate for multi-sided parts because it removes re-clamping. For a flat part, a 3-axis machine is equally accurate and cheaper.
What does 3+2 mean?
Positional 5-axis machining: the two rotary axes orient the part, lock, and the cut is made with three linear axes.
Related pages
- Capabilities
CNC milling and 5-axis machining
3-, 4- and 5-axis milling: 5-axis to 800 × 800 × 550 mm, frames to 1,600 × 800 × 700 mm.
- Technical guides
Tolerancing 5-axis parts
Datums, position and profile tolerances, general tolerances and measurability.
Send us your drawing.
STEP, IGES, DXF or PDF. Quotation within 2–15 business days, depending on size and complexity.