Choosing the Right Material for CNC Machined Parts: A Quick Guide

One of the most frequent questions we receive from overseas clients is: “We need a strong, lightweight metal part. Should we use Aluminum or Steel?”

Choosing the wrong material is a costly mistake. It leads to parts that are too heavy, corrode prematurely, or fail under load. At our CNC facility, we see this happen when designers select materials based on textbook properties rather than real-world machinability and application environment.

To save you from expensive redesigns, here is our internal guide to selecting the best metal for your CNC machined parts.

The Big Three: Aluminum vs. Stainless Steel vs. Carbon Steel

These three families represent 90% of the parts we manufacture. Here is how they compare in our machines:

Beyond the Basics: Specialty Alloys

Sometimes, standard metals won’t cut it. Based on our project archives, here are the specialty materials we recommend for extreme conditions:

• Brass (C360): Best for electrical connectors and decorative parts. It machines incredibly fast and offers natural antimicrobial properties.

• Titanium (Grade 5 Ti-6Al-4V): Used for aerospace and medical implants. It offers the highest strength-to-weight ratio but requires low cutting speeds and specialized coolant to prevent burning.

• Copper: Excellent for thermal management (heat sinks). However, it is gummy and difficult to machine; we recommend sharp tools and high rake angles.

FAQ: Insider Advice from Our Engineers

Q: Can I substitute 7075 Aluminum for 6061 to save weight?

A: No, that’s a common misconception. 7075 is actually slightly denser than 6061. Choose 7075 for higher strength, not lower weight. If weight is your primary concern, stick with 6061 or consider thinner wall sections.

Q: My part needs to be magnetic. Which material should I choose?

A: Most stainless steels (304/316) are non-magnetic. If you need magnetism, choose 430 Stainless or Carbon Steel. Note that 303 Stainless (the easiest to machine) is slightly magnetic, while 304 is not.

Q: Does the material choice affect the lead time?

A: Yes. Standard 6061 Aluminum and 12L14 Steel are always in stock. However, specialty alloys like Titanium or Inconel can take 1-2 weeks to procure, adding significant time to your order.

Q: What is the cheapest material for a prototype?

A: For prototypes where mechanical properties aren’t critical, 6061 Aluminum is the cheapest. It machines quickly, produces less tool wear, and the raw material cost is moderate. Avoid exotic alloys for initial testing.