Knowing Your Material Options for CNC Machining

Jun 12, 2019

Knowing Your Material Options for CNC Machining

CNC machining is a highly accurate and repeatable manufacturing process used for prototypes and production parts. A subtractive process, CNC machining involves cutting material away from a solid block using computer-controlled cutting tools like drills and lathes. The result is a professional-quality part suitable for mechanical use.

One of the biggest advantages of CNC machining is its material versatility. Though commonly used to cut aluminum and steel alloys, the process is equally suited to a wide range of engineering metals, as well as high-quality plastics. Many of these materials can be treated with a variety of finishing options after machining.

Before diving straight into a CNC machining project, it’s worth getting acquainted with the large number of material options at your disposal.

Prioritizing Material Properties

Given the vast array of material options for CNC machining, it is highly likely that there will be a suitable material for your prototyping or production job.

Finding that material, however, depends on your priorities: do you need a metal with exceptional mechanical properties, such as a titanium alloy? Or is speed a priority, leading you to more machinable materials like Aluminum 6061 or a plastic like Delrin? Do you simply want a machined prototype at the lowest possible price?

Factors to consider when choosing a material for CNC machining include:

  • Price
  • Machinability
  • Strength
  • Weight
  • Chemical resistance
  • Thermal resistance
  • Hardness
  • Weldability

Of course, it won’t always be possible to find a material that meets all of your criteria to the highest possible degree. The very strongest machining materials are rarely the cheapest, and choosing added strength may lead to a reduction in chemical resistance or some other property.

Identify which properties are of greatest importance and work from there.

Selecting a Material

The best way to determine the best and most suitable CNC machining material is to consult an expert like RapidDirect. Once we know the outline of your project, we can help you come to a decision regarding materials, finishing processes and much more depending on your goals, budget and timeframe.

However, if you want to draw up a shortlist of potential machining materials in advance, it is worth getting acquainted with the options out there.

From versatile aluminum alloys to specialist engineering plastics, here are some of the materials from which CNC parts can be made:


Aluminum is a versatile metal that is affordable and easy to machine. It has a good strength-to-weight ratio, and its sheer variety means there is a suitable alloy for most machining projects.

Common aluminum grades include:

Grade Example application Advantage Disadvantage
6061 General fabrication Versatility  
7075 Aerospace Strength Weldability
5052 Marine Corrosion resistance  
3003 Food Formability Not heat treatable

RapidDirect also offers aluminum machining in grades 1060, 1100, 2024, 3004, 5083, 5754, 6082, 6063, 6083, 7050, 5A12 and 5A02.

Stainless Steel

Widely used in a number of industries due to their corrosion resistance and other desirable properties, stainless steels come in a variety of grades, many of which are suitable for CNC machining.

Common stainless steel grades include:

Grade Example application Advantage Disadvantage
304 Medical devices Corrosion resistance  
303 Aerospace Machinability Slightly lower corrosion resistance
316 Architecture Corrosion resistance Price


Mild steels and alloy steels come in many machinable variants, many of which are suitable for general fabrication, tooling and specialist industries.

Common steel grades include:

Grade Example application Advantage Disadvantage
A36 Construction Strength  
1018 Machinery Weldability Machinability
Alloy Steel 4130 Aerospace Toughness  

RapidDirect also offers steel machining in Alloy Steel 4140 and ASTM A36.

Other Metals

Beyond aluminum and steel, it is also possible to machine metals such as brass, copper, titanium and zinc, offering engineers a wider range of physical properties for their parts. Copper, for example, is an excellent conductor, making it suitable for electrical parts.

Other machinable metals include:

Grade Example application Advantage Disadvantage
Brass C360 Industry Machinability  
Copper Electrical components Thermal conductivity  
Titanium 6Al-4V Aerospace Strength-to-weight Price

RapidDirect also offers metal machining in other brass, copper and titanium grades, as well as Zinc Sheet Alloy 500.


CNC machines are equally capable of cutting plastics, which may be preferred for cost, electrical insulation or other reasons. Plastics are often a suitable prototyping material when the final part will be made with injection molding.

Machinable plastics include:

Grade Example application Advantage Disadvantage
POM (Delrin) Mechanical parts Machinability Acid resistance
PTFE (Teflon) Electrical components Heat & chemical resistance  
ABS Consumer products Impact strength Heat resistance

RapidDirect also offers plastic machining in Acrylic, G-10 Garolite, Nylon, PEEK, Polycarbonate and Polypropylene.

Contact RapidDirect for a fast CNC machining quote.

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