Definition
3-axis machining moves a cutting tool along three linear axes (X, Y, Z) relative to the workpiece. It is the baseline capability of most milling machines and can produce a wide range of features, but cannot reach geometry that requires the tool or part to tilt, such as an undercut or a feature on a compound angle.
Why 3-axis reach is a natural cost baseline
A part that fits entirely within 3-axis reach from one or a few flat-face setups is usually the cheapest to machine; the same part with one undercut or angled feature can force a jump to 5-axis or an extra, more complex setup.
Where 3-axis machining applies
Implied when all features are reachable from directions perpendicular to a small number of flat faces, without any undercuts or compound-angle features.
Common mistakes
Assuming any part can be finished in 3-axis just because it looks simple; a single undercut or angled boss can force a more complex setup or a 5-axis machine even on an otherwise straightforward part.
A part that fits entirely within 3-axis reach from one or a few flat-face setups is usually the cheapest to machine; the same part with one undercut or angled feature can force a jump to 5-axis or an extra, more complex setup.
See how Blake reviews a partFrequently asked questions
What can't 3-axis machining reach?
Undercuts, and features on faces that aren't reachable perpendicular to the part's current orientation, such as compound-angle bosses or holes.
Is 3-axis machining always cheaper than 5-axis?
Usually for parts it can fully reach, since the machines and programming are typically simpler; but a part needing several 3-axis setups can cost more than one clean 5-axis setup.
Is 3-axis the same as 3+2 machining?
No, 3+2 machining tilts the part between cuts to reach different faces but still cuts with 3-axis linear motion at a time; true simultaneous 5-axis moves all axes together during the cut.