When is 5-axis machining worth it?

For parts with features on many faces or at compound angles, and for curved surfaces such as impellers and mould cores. Simple flat parts are cheaper on a 3-axis VMC.

What is 3+2 machining?

The part is tilted to a set angle by the two rotary axes and then machined with normal 3-axis moves; it covers most multi-face work.

Is 5-axis more accurate?

For multi-face parts, yes, because the part is not re-clamped between faces. For a single face, a good 3-axis machine is just as accurate.

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5-axis machining centre

Also called: 5 axis CNC, 5-axis VMC, five axis machining, simultaneous 5-axis, 3+2 machining

A 5-axis machining centre moves the cutter along X, Y and Z and also tilts and rotates the part (or the spindle head). It reaches almost every face and angle in one setup, so complex parts such as impellers, mould cores and aerospace parts are made more accurately and with fewer fixtures.

Quick facts

Axes: X, Y, Z plus two rotary axes (A/B/C)
Common design: Tilting rotary table (trunnion) on a VMC frame
Modes: 3+2 (positional) or simultaneous 5-axis
Typical accuracy: Around ±0.01 mm; very good across faces
Programming: Needs CAM software and skilled programmers
Cost: Higher hourly rate than a 3-axis VMC

3+2 or simultaneous 5-axis?

3+2 (positional): the part is tilted to an angle and held while 3 axes cut; most parts needing several angled faces
Simultaneous 5-axis: all five axes move together; smooth curved surfaces such as impellers, turbine blades and sculpted moulds

Advantages

Many faces in one setup: features line up accurately
Fewer fixtures and less handling
Shorter tools reach deep features at an angle, giving better finish
Complex shapes that a 3-axis machine cannot reach

Limits

Higher machine-hour rate and programming time
Simple prismatic parts are usually cheaper on a 3-axis VMC
Part size is limited by the rotary table

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Questions

When is 5-axis machining worth it?: For parts with features on many faces or at compound angles, and for curved surfaces such as impellers and mould cores. Simple flat parts are cheaper on a 3-axis VMC.
What is 3+2 machining?: The part is tilted to a set angle by the two rotary axes and then machined with normal 3-axis moves; it covers most multi-face work.
Is 5-axis more accurate?: For multi-face parts, yes, because the part is not re-clamped between faces. For a single face, a good 3-axis machine is just as accurate.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 8 October 2026.