Engineering · Comparison
Both use the same five-axis machine. The difference is whether all five axes move during the cut (true 5-axis) or whether the part indexes to a fixed orientation and machines like a 3-axis (3+2). The choice shapes programming time, cycle time, and surface finish — and ~85% of 5-axis work runs better as 3+2.
| Spec | 5-axis simultaneous | 3+2 indexed |
|---|---|---|
| Axis motion | Up to 5 axes moving simultaneously while cutting | 5 axes available, but only 3 (X/Y/Z) move while cutting; A and B index between cuts |
| Surface finish on contours | Smooth, blended | Stair-stepped between indexed positions |
| Programming complexity | High — requires CAM with full 5-axis post + simulation (Vericut) | Standard 3-axis CAM with rotational re-orientation |
| Machine cost | Highest — true 5-axis machining centers | Same machine, simpler programming |
| Cycle time | Slower per pass — feed-rate limited at extreme axis positions | Faster — full feed-rate on each indexed face |
| Cutter reach | Better — tilt the head into deep features | Better — tilt fixture, use shorter tools |
| Setup count | 1 | 1 (with re-fixture for orientation if needed) |
| Fixture complexity | Low (single hold) | Low (single hold) |
| Best for | Impeller blades, conformal cooling, blended optical surfaces | Aerospace brackets, 5-sided prismatic parts, anything where surface finish doesn't need blending |
5-axis simultaneous
Impeller and turbine blade surfaces, optical mirrors, conformal cooling channels, undercut features. Anything where the surface needs to flow continuously without stair-stepping. The cost: longer programming, higher CAM license tier, mandatory simulation, slower feed rates at extreme axis positions.
3+2 indexed
Aerospace brackets, defense fittings, optical mounting plates, structural components — anything with planar features at varied angles. Same productivity benefit (no re-fixture, no stack-up error) without the programming and feed-rate cost. The vast majority of 5-axis work is actually 3+2.
Practical guidance
There’s no surface-blending advantage to simultaneous motion when each finished surface is flat. Index, mill, index, mill — done.
3+2 leaves stair-step lines visible on cross-section. Simultaneous blends the surface following the actual geometry.
Full feed rates instead of constrained simultaneous-axis paths. For cost-sensitive production, this matters.
Vericut or equivalent. Collision risk is high enough that running unsimulated programs is genuinely dangerous to the machine. 3+2 is much more forgiving.
Our Kitamura Mytrunnion 4G handles both. The decision is at the CAM stage, not at the machine purchase.
Keep exploring
Match part geometry, material, and volume to the right in-house process.
The same routing decision applied to turning.
Design geometry so it routes cleanly to one setup.
Compare 3+2 and simultaneous cycle times for your part.
How finish and form callouts drive the 5-axis vs 3+2 choice.
Technically reviewed by the True Precision Machining engineering team · Last reviewed June 2026
We run true 5-axis and 3+2 indexed work on the same machines and choose the strategy that holds your tolerance at the lowest cost. Send a drawing or STEP file.
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