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Aluminium and stainless steel are two of the most popular choices for CNC machined parts. Each brings unique advantages depending on your industry, design priorities, and performance requirements. This guide breaks down aluminium vs stainless steel to help you make a confident, cost-effective material choice.
Both metals are commonly used in precision engineering, but they behave quite differently in machining and real-world applications. While they share qualities like corrosion resistance and availability, their performance and manufacturing characteristics vary significantly. Understanding those differences from the start can save you time, money, and production headaches.
Here’s a quick side-by-side of the key material properties:
Aluminium is widely used in industries where weight reduction, speed, and precision machining are critical. Its high strength-to-weight ratio and conductivity make it ideal for a range of components, including:
Stainless steel is preferred when strength, corrosion resistance, and long-term durability are non-negotiable. You’ll often find it in:
Aluminium and stainless steel perform differently when it comes to strength, weight, and corrosion resistance. These differences determine not just where they’re used, but how well they hold up over time. Understanding these key performance traits is essential to choosing the right material for your CNC parts.
When comparing aluminium vs stainless steel strength, stainless steel is the stronger material by far. With tensile strengths reaching up to 1300 MPa in certain grades, it’s built for demanding environments and high loads. Aluminium, while softer, has a strong strength-to-weight ratio that makes it highly effective in lightweight structural applications.
One of the most noticeable differences in aluminium vs stainless steel weight is density, aluminium is about one-third as heavy. This makes it ideal for designs where weight reduction improves speed, efficiency, or energy usage, such as in aerospace, electric vehicles, or automation systems. Lightweight parts are also easier to handle and assemble, helping to streamline production.
Aluminium forms a protective oxide layer that helps it resist corrosion in dry environments. But in marine, acidic, or salty conditions, it can deteriorate quickly unless treated. Stainless steel is naturally resistant to corrosion, with grades like 316 designed to withstand harsh chemical and environmental exposure, a clear advantage in the aluminium vs stainless steel corrosion debate.
Material choice doesn't just affect how a part performs, it shapes the entire CNC machining process. Things like tooling wear, cycle times, achievable tolerances, and design complexity all vary depending on the metal. Here's how aluminium vs stainless steel cost and usability stacks up in the workshop.
Aluminium is easier on machines and tooling. It cuts quickly, produces less heat, and results in faster turnaround times with fewer tool changes. That’s why many engineers choose aluminium machining services when speed and efficiency matter.
Aluminium handles tight tolerances with less resistance and finishes beautifully, often needing minimal post-processing. Stainless steel can match that precision but usually requires more care:
For detailed features or smooth surface requirements, aluminium is often the more forgiving option.
Aluminium parts typically reach the finish line faster. Its machinability reduces setup times and shortens production cycles, making it ideal when time is tight. Use aluminium if your part involves:
Stainless steel takes longer to machine but earns its keep in tough environments, see our comparison on Hard vs. Soft Metal Machining for a deeper look.
The true cost of a machined part goes far beyond the price tag on raw materials. You also need to consider machining time, tooling, scrap rates, and the cost of delays. Here’s how aluminium alloy vs stainless steel compares when it comes to cost and sourcing.
Aluminium can seem more expensive by weight, but it’s not always the case when you look at volume. Its lower density means you get more material per kilogram, which can reduce total spend for larger parts. Stainless steel is heavier and often more economical for smaller, high-strength components that don’t need much raw material.
Aluminium is easier on both tools and machines. This leads to:
Stainless steel is tougher to cut and requires more care, which increases machining costs over time, especially for complex parts or high-volume runs.
Both materials are widely available across the UK and European markets. That said, certain aluminium alloys, like aerospace-grade 7075 or marine-grade 5083, can be subject to longer lead times. Stainless steel is globally standardised and easier to source consistently, which is why it’s a dependable material for many of our CNC machining services.
There’s no one-size-fits-all when it comes to aluminium alloy vs stainless steel. The best choice depends on your priorities, from operating environment and part geometry to machining complexity and finish. Use the guidance below to help narrow down the right fit for your application.
Aluminium is a strong contender when speed, lightness, and flexibility are top priorities. It’s easy to machine, holds tight tolerances, and offers excellent thermal and electrical conductivity. For many engineers, it’s the go-to material for precision parts that don’t need to bear extreme loads.
Aluminium is your best bet when:
It’s also ideal for electronics housings, cooling components, and lightweight frames — all common areas for aluminium machining services.
Stainless steel delivers high performance where strength and resilience are critical. It’s better suited to tough environments and high-pressure conditions, especially when exposure to heat, chemicals, or moisture is expected. If your application demands durability and longevity, stainless steel is often the smarter long-term investment.
Stainless steel is the right choice when:
Stainless is tough, long-lasting, and widely used in industrial, marine, and medical settings. If your project demands precision and durability, our stainless steel CNC machining capabilities can help you get the job done right.
Material selection isn’t just about specs, it’s about real-world conditions and priorities. Your machining partner can flag risks, suggest alternatives, and help optimise for cost, finish, and turnaround. Not sure where to begin? Our guide on How to Choose the Right Metal for Machining is a great place to start.
