CNC machining: a material guide 

Computer Numerical Control (CNC) machines offer a host of advantages, from reduced human error to increased production speed. This article explores a perhaps more overlooked benefit: their compatibility with different materials.


Steel, acrylic, composites — the list goes on. But what are the most common materials for CNC machining? What are they used for? And how do manufacturers know which ones to pick?


A CNC machine manufacturing a product from metal materials.

CNC material selection


CNC machines are ideal for manufacturing a range of parts and components from a generous breadth of materials. The most common CNC materials are metals and plastics, both of which offer their pros and cons.


However, when choosing a material, there are many factors to consider.


Think of it as a list of criteria. To successfully find the suitable material, every box needs to be ticked. All these factors will affect the final product and its manufacturing process, from the material’s strength and cost to its functionality. That’s why it’s essential to consider these in-depth beforehand.


So, what things should you keep in mind before choosing a material for CNC machining?

CNC material criteria


Typically, a CNC material is selected depending on the size of the component, its applications and machining environments. Certain materials are far more suitable than others when considering the scale of the project, what’s being made and its intended use.


There’s also a range of physical properties to consider, like whether the component needs to be sturdy and able to withstand stress or whether it should present high insulation properties and electrical conductivity.




Different materials present different levels of corrosion resistance, heat resistance, and temperature ranges, which dictate the environments they’re suited to and the resulting types of components.


After all, no one wants a component that performs poorly because it can’t withstand its intended environment. This applies not only after manufacturing but also during machining, as some materials chip when exposed to high machining temperatures.


Environments will also affect other characteristics, like flame retardance and chemical and UV resistance. Materials for catering and medical environments must also be medical and food-grade.


Strength and weight


Most components require a long lifespan to ensure value. Stronger components typically offer longer lifespans as they are less vulnerable to constant use, demanding environments, and general wear and tear.


However, while it’s important for your parts to last, some high-strength materials are notoriously tricky to machine, which can create production delays.


The same can be said about material weight. Stronger materials are often heavier and require bigger CNC machines for manufacturing, making production pricier. If you’re looking for a lighter and cheaper option, it’s best to opt for something low-density. Not only is this more practical during the manufacturing process, but it’s also more efficient once the component is in use.




Paintability and surface finishes are paramount for projects where aesthetically pleasing parts are a must. A CNC material is better when it’s easily polished, painted and has a smooth surface.


Metals, which can be shiny, smooth, or matt, offer more options for smoother finishes. That said, looks aren’t the only advantage of a smooth surface — they also reduce friction during use, which leads to better performance for a longer period.




Another key factor to consider is budget.


The cost of materials varies significantly, especially when high quantities are required. Composites and plastics aren’t as inclined to break the bank, offering a more economical option, while high-grade metals are less budget-friendly.


CNC machines themselves are already expensive, and the process can take a lot of time and money to complete. This makes it crucial that materials are cost-effective while still meeting your criteria.


Metal bolts and screws, like the kinds made from CNC machines and CNC materials.



We work hard at Sheldon Precision to manufacture top-quality CNC machined parts. To do this, we use customer ideas, samples, drawings, and designs, as well as a variety of metals, including aluminium, brass, carbon steel, stainless steel, and steel alloys.


However, choosing a metal can be tricky. There are so many out there, and they’re all slightly different. That’s why we’ve provided some extra guidance below with a few of the most common metals for CNC machining.




A common CNC material is aluminium, which is no surprise considering its lightweight structure and resilience.


Not only does it give manufacturers a fantastic strength-to-weight ratio, but it also offers high machinability. It has solid thermal and electrical conductivity and is a more cost-effective option than other materials on the market, particularly in mass production and high-volume batches.


Several aluminium grades are available. 6061 and 7075 are advised for applications where weight is a concern. They’re popular for automotive engine parts and aerospace frames, though they are also used in a range of consumer electronics and construction parts. Likewise, 5052 and 2024 are ideal for marine and aerospace applications, respectively.


Stainless Steel


With its high wear resistance, stainless steel is a brilliant CNC material for projects requiring strength and corrosion resistance against chemicals and moisture. It’s highly versatile and maintains its appearance throughout use, offering a sleek finish without compromising functionality.


Stainless steel is perfect for precision machining and isn’t too expensive, though different grades can pose some problems in machinability due to their hardness.


Stainless steel comes in a variety of grades suitable for CNC machining, though 316 is one of the most commonly used. Since it’s a hygienic option and doesn’t rust easily, it lends itself to many medical equipment and marine applications. As for other grades, such as 303 and 304, they’re often implemented when making a range of screws and bolts.




If you’re looking for a CNC material that meets aesthetic requirements, brass is the way to go. Not only is it robust and easily machined, but it provides a smooth surface finish and a pleasant golden finish.


Brass is a material with good electrical and thermal conductivity, and it is perfect for use where transferring heat and electricity is necessary. It can also be machined quickly and easily, shortening the production time, and its resistance against corrosion keeps it from rusting when exposed to moisture. C464 brass is particularly ideal for marine and saltwater environments.


The biggest snag is its price point, which might be an issue for small companies with less flexible budgets.


Titanium and Alloys


A CNC materials for high-strength applications, titanium and its alloys are fantastic options. Titanium is tough and sturdy while remaining lightweight, and its corrosion resistance makes it perfect for more humid environments where rusting can be a problem.


Titanium is used extensively in components and parts for the military, medical, and aerospace industries, though its biocompatible and non-toxic qualities are highly favourable for the biomedical industry. However, it can be challenging to work with since its low thermal conductivity causes the material to heat up when tools move too quickly.


There are multiple grades of titanium out there, all varying in strength and machinability. As a result, titanium can be used to craft a multitude of components across a wide range of industries.




Copper is undoubtedly perfect for electrical components. It offers impressive thermal and electrical conductivity, high ductility, and excellent corrosion resistance. What’s not to love?


Although it’s typically used for magnetic devices, electrical wiring, and plumbing parts, its sleek appearance and malleability make it ideal for other uses, such as jewellery.


Similar to brass, copper can be costly, so it might not always be the most economical option. It’s also very soft, which can result in tool wear and make it difficult to machine at higher temperatures.


Carbon Steel and Alloys


If components need to be versatile and durable, carbon steel and its alloys are a reliable option.


Carbon steel is well-favoured in CNC machining because it is easy to machine and ductile. It is also compatible with a range of heat treatment techniques and is perfect for wear-resistant applications. It offers good machinability and weldability.


While you might not be keen on carbon steel’s appearance, it’s still perfect for industrial applications and mechanical fasteners. It isn’t as corrosion-resistant as materials like stainless steel, either. Properties can differ, however, depending on the carbon content — for instance, low carbon content offers increased malleability, whereas high carbon content is typically stronger.


A CNC laser machine manufacturing components from CNC materials.



Like metals, plenty of plastics can be used in CNC machining. Some popular CNC plastic options include ABS, acrylic, polycarbonate, nylon and polypropylene.




Easily machinable, ABS plastic is a CNC material renowned for its tensile strength and toughness, as well as its chemical and impact resistance. CNC machining helps it retain these qualities while achieving tight tolerances.


It’s a fantastic option when resilience is key to your component. ABS also offers aesthetic value as it can be easily coloured. It is cost-effective and ideal for use in several applications, including creating automotive components and enclosures.


On the downside, ABS isn’t always compatible with high-heat environments and is non-biodegradable, meaning it cannot be broken down naturally. Because of this, it’s important that it be recycled rather than thrown away.




Acrylic plastic is an excellent alternative to glass. It is lightweight and resistant to various chemicals. Its clarity makes it ideal for transmitting light while withstanding prolonged UV exposure, preventing surfaces from yellowing.


That said, there are better options than acrylic for parts that must be tough and resilient to damage. Other plastics are more suitable for these applications.




Polycarbonate is a popular choice because of its properties, such as high strength, dimensional stability, and transparency.


Polycarbonate’s clarity makes it suitable for the production of lenses, safety glasses and electronic displays. It offers great temperature resistance and impact strength, making it a go-to option for medical devices, automotive parts, and applications with high temperatures.


Polycarbonate is less practical when parts are prone to scratching or denting. It also offers less UV resistance than acrylic, which means that, without UV stabilisers, sitting in the sun for too long can cause it to turn yellow and turn parts too brittle to last the long term.




Nylon is a common plastic for CNC machining due to its durability and wear resistance.


It presents chemical stability, hardness and good wear resistance, rendering it perfect for crafting a range of components from screws, gears and washers to medical devices and electrical housings.


Different types of nylon offer different advantages. For example, nylon 6/6 is less flexible than Nylon 12 but provides better wear resistance. It’s best to weigh up your options and decide which is best for your component.




Another plastic ideal for CNC machining is polypropylene, with properties such as chemical resistance, durability and flexibility.


Polypropylene can tolerate high temperatures, perfect for precise parts and complex geometries. Its mechanical strength ensures that components can remain lightweight with good rigidity.


However, it’s important to weigh up its pros with its cons. Polypropylene is often more expensive than other plastics and can extend the machining process, taking longer to achieve perfect results depending on machine compatibility.


A close up of a pile of wooden planks.

Other CNC materials


In addition to the vast range of plastics and metals available, CNC machines allow for the manufacturing of wood, composite, and foam components.


The kinds of wood, composites and foam used tend to vary depending on the CNC machining service. Hardwood, softwood and plywood can be used to create various products that benefit from their hardness and toughness. At the same time, foams like polyethene ensure smooth and lightweight structures that don’t lack durability.


That marks the end of our CNC machining materials masterclass. We hope you learned something new about the materials you use and that you refer to this guide when choosing the right materials for your next project.

Supporting UK businesses


Are you looking for support with your project? Sheldon Precision is here to help. With a full CNC manufacturing facility, we provide a premium service to exact customer specifications.


Contact us today for more information.