steel vs aluminium cnc machining · 7 min read
A practical comparison covering machinability, weight, surface finish and cost.
Published: · CNC Turkey
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Steel and aluminium are the two most commonly used metal groups in CNC machining. Both are highly machinable, but they differ significantly in density, strength, corrosion resistance and cost.
This guide explains which material is more suitable under what circumstances, using practical criteria.
Aluminium (6082, 7075) machines 3-5x faster than steel. This significantly reduces machine time cost and partially compensates for the higher per-kg material price.
Stainless steel (316L, 304) is among the most challenging common materials to machine. High tool wear, low cutting speeds and frequent tool changes increase cost.
Aluminium density is approximately 2.7 g/cm³ versus 7.8-8.0 g/cm³ for steel. This 3x density difference makes aluminium the clear choice in weight-critical applications (aerospace, automotive, portable equipment).
However, for load-bearing or impact-loaded applications, steel remains superior. Alloy steels such as 42CrMo4 are preferred for shafts, gears and fasteners requiring high fatigue strength.
Aluminium has natural corrosion resistance through its oxide layer. Anodising further enhances this. Structural steels (S235, 1.7225) require protection in humid or chemical environments.
Stainless steel (304/316L) is preferred in applications requiring both mechanical strength and high corrosion resistance (food, medical, chemical industries).
FAQ
Structural steel has a lower per-kg material cost. However, aluminium machines much faster, which can bring total unit cost to similar levels. For small, lightweight parts aluminium is often more economical overall.
7075 is used for high-strength applications (like aerospace components) and costs approximately 40% more than 6082. 6082 is the most common industrial aluminium alloy offering good strength and excellent corrosion resistance.
Stainless steel tends to work-harden during cutting, causing high tool wear. This requires slower cutting speeds, more frequent tool changes and consequently higher machine time costs.
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