Guides / Process

3+2 vs Simultaneous 5-Axis: What the Difference Means for Your Part

September 20, 2026

Both methods run on the same 5-axis machine. The difference is simple: in 3+2 the rotary axes tilt the part and then stay still while the tool cuts, and in simultaneous 5-axis all five axes move while the tool is in the material. That one difference changes programming time, cycle time and the price you pay.

How 3+2 machining works

The machine rotates the table or tilts the head to a fixed angle, locks it and cuts like a normal 3-axis mill. When it finishes that face it rotates to the next angle and repeats. The “3+2” name means three linear axes cutting plus two rotary axes used only for positioning.

For a housing with bores on four sides, 3+2 is usually the right answer. The part is clamped once, every face is reached from the right angle and the features line up because nothing was unclamped between them. Programming is close to 3-axis programming, so CAM time stays low.

Typical 3+2 parts:

• Pump and valve housings with ports on several faces
• Brackets and manifolds with holes at compound angles
• Enclosures with features on five sides
• Fixtures and tooling plates with angled locating holes

How simultaneous 5-axis works

In simultaneous machining the rotary axes keep moving during the cut. The tool can follow a curved surface and stay at the same angle to it the whole way along. That matters when the surface itself is the product.

Simultaneous 5-axis is needed for impeller blades, turbine airfoils, ports with changing cross sections and organic medical shapes. It also lets a shorter tool reach deep areas by tilting around obstacles, which reduces chatter and improves finish.

The cost is in programming and verification. Toolpaths are more complex, collision checking takes longer and the first part often needs more time on the machine to prove out. On a quantity of five that setup cost dominates the quote.

Side by side

	3+2 positional	Simultaneous 5-axis
Rotary axes during cutting	Locked	Moving
Best for	Prismatic parts, angled holes and faces	Freeform surfaces, blades, blends
CAM programming	Close to 3-axis	Longer, needs collision checks
Cycle time on flat faces	Short	No advantage
Surface finish on curves	Stepped, needs more passes	Smooth, fewer passes
Price on low quantities	Lower	Higher setup share

Which one does your part need?

Look at the surfaces that matter. If they are flat faces, straight holes and pockets, even at odd angles, 3+2 will make the part. If any functional surface curves in two directions, such as a blade, a blended port or an anatomical shape, you are looking at simultaneous work for at least that feature.

Many real parts are a mix. A shop might rough and drill a housing in 3+2 and then finish one blended port with a simultaneous toolpath. That is normal and it is one reason not to over-specify the method on your RFQ.

What to put on your RFQ

Describe the part and its critical surfaces rather than the machining method. These details help a shop quote accurately the first time:

1. A STEP file plus a PDF drawing with tolerances
2. Which surfaces carry finish requirements, with the Ra value
3. Which features must hold position relative to each other
4. Quantity now and expected repeat volume

If a surface finish requirement truly needs continuous tool contact, say so in a note. Otherwise let the shop pick. A good 5-axis shop will choose the cheapest method that meets the drawing, and quotes from different shops are easier to compare when each chose freely.

The short version

3+2 covers most parts people send to 5-axis shops and it costs less. Simultaneous 5-axis earns its price on curved functional surfaces. Send the geometry, mark what matters and let the shop decide how to cut it.

Frequently asked questions

Keep reading

• Thermal Growth on 5-Axis Machines and How Shops Control It
• Collision Checking and Machine Simulation Before a 5-Axis Run