If you’re running a job shop or production facility, you’ve probably asked the question: “Do we upgrade to a 5‑axis machine, or keep running 3‑axis mills with a trunnion?”

It’s a big decision — and an expensive one. True 5‑axis machining opens the door to faster cycle times, fewer setups, and more complex parts. But trunnion‑equipped 3‑axis mills can deliver surprising capability at a fraction of the cost.

This guide breaks down the advantages, disadvantages, and real‑world tradeoffs between:

• Standard 3‑axis vertical machining centers
• 3‑axis VMCs with 4th/5th‑axis trunnion tables
• True 5‑axis CNC machining centers

By the end, you’ll know exactly which option fits your shop’s work, budget, and long‑term goals.

🧱 What Is 3‑Axis Machining?

A standard 3‑axis VMC moves in X, Y, and Z. The spindle stays vertical, and the part stays fixed.

Advantages

• Lowest cost of ownership
• Easiest to program
• Most operators already trained
• Great for prismatic parts
• Simple workholding

Disadvantages

• Multiple setups required for multi‑face machining
• Higher chance of stack‑up error
• Longer cycle times
• Limited access to undercuts and complex geometry

Best For

• Flat or prismatic parts
• Low‑complexity components
• Shops with lower mix and higher volume

🔄 What Is a 3‑Axis Mill with a 4th/5th‑Axis Trunnion?

This is a hybrid solution: a standard VMC equipped with a rotary table or trunnion that adds A‑ and B‑axis rotation.

Advantages

• Much cheaper than a true 5‑axis machine
• Allows 3+2 positioning (indexing, not simultaneous)
• Reduces setups dramatically
• Fits in the footprint of a standard VMC
• Uses familiar controls and programming workflows

Disadvantages

• Not true simultaneous 5‑axis
• Limited rigidity compared to built‑in 5‑axis machines
• Trunnion reduces table space and Z‑height
• Workholding becomes more complex
• Accuracy depends heavily on trunnion quality and calibration

Best For

• Shops wanting 5‑sided machining without the cost
• Medium‑complexity parts
• Mold bases, fixtures, aerospace brackets, medical components

🌀 What Is True 5‑Axis Machining?

A true 5‑axis machine has integrated rotary axes built into the machine’s structure — not bolted on.

This allows simultaneous 5‑axis motion, enabling complex surfacing, sculpted geometry, and ultra‑efficient toolpaths.

Advantages

• True simultaneous 5‑axis capability
• Fastest cycle times
• Best surface finish
• Minimal setups
• Highest accuracy for multi‑face machining
• Ideal for complex aerospace, medical, and mold work

Disadvantages

• Highest machine cost
• Requires advanced CAM programming
• Operators need more training
• Workholding can be more specialized
• Higher maintenance and calibration requirements

Best For

• High‑mix, high‑complexity work
• Aerospace, medical, mold & die
• Shops needing tight tolerances on multiple faces

⚙️ When a Trunnion Makes More Sense Than a True 5‑Axis

A trunnion is the sweet spot when you want:

• 5‑sided machining
• Fewer setups
• Better accuracy
• Faster cycle times

…but don’t need:

• Simultaneous 5‑axis surfacing
• Complex organic geometry
• Aerospace‑level tolerances

For many job shops, a trunnion-equipped VMC is the best ROI upgrade.

🚀 When You Should Invest in a True 5‑Axis Machine

A true 5‑axis machine is worth it when:

• You’re machining complex 3D surfaces
• You need tight tolerances across multiple faces
• You want to eliminate 80–90% of setups
• You’re competing in aerospace, medical, or mold & die
• You need the fastest cycle times possible

If you’re quoting work that requires simultaneous 5‑axis toolpaths, a trunnion simply won’t cut it.

🧭 So Which One Should Your Shop Choose?

Choose 3‑Axis if:

• Your parts are simple
• You’re budget‑constrained
• You don’t need multi‑face machining

Choose 3‑Axis + Trunnion if:

• You want 5‑sided machining
• You want fewer setups
• You want better accuracy without the cost of a full 5‑axis

Choose True 5‑Axis if:

• You machine complex geometry
• You need simultaneous 5‑axis
• You want the fastest cycle times and highest accuracy

📞 Conclusion

Choosing between 3‑axis, trunnion‑equipped, and true 5‑axis machining comes down to part complexity, budget, and long‑term goals. Each option has a place — the key is matching the machine to the work.

If you’re evaluating your next machine purchase, Concord Machine Tools can help you compare options from Haas, Mazak, Okuma, Doosan, Makino, and more.

Browse our current CNC machining centers or contact us for recommendations based on your workload.