What materials can a CNC machine cut? CNC machining works with lots of different materials. Choosing the right one is key for your project. The material impacts how easy it is to machine and the final product quality. So, it’s important to pick wisely.
What to Check In CNC Machining Material?
When you’re picking a material for CNC machining, there are a few things to think about. You need to consider what the material is like to work with and if it will do the job you need it to do.
Machinability
Definition
Machinability is basically how easy a material is to cut and shape with CNC machines. It tells you how well a material behaves during machining.
Impact on
Good machinability means faster production, less tool wear, and better finishes. If a material is easy to machine, you can make parts quickly and at an affordable price.
Low Machinable Materials
Some materials are harder to machine than others. These are called low machinable materials. They can be tough on tooling, take longer to machine, and might not give the best surface finish.
Mechanical Properties:
OK, so we need to deal with mechanical properties now. By the same sequence, mechanical properties reveal how a material will behave when we push it, or pull it, or try to alter its shape. In CNC machining materials, this part is very important because the right material impacts the performance and the life of the part significantly.
Strength
Strength refers to how robust a material is. It measures how much stress a material can endure before failure. Strength exists in various forms, with one of the most common being tensile strength. What is tensile strength? Simply put, it is assessed by applying a tensile load to determine how much it can stretch before breaking.
Hardness
Hardness refers to the ability of a material to resist scratches. Hardness also refers to what it takes to alter the surface of a material. For instance, CNC machining companies measure hardness by pushing something tough into the material and how deep it penetrates.
Ductility
In simpler terms, ductility is the extent to which you can stretch a material without breaking it. For example, gold is highly ductile. So gold wires are made because of the ductility of gold.
When something is ductile, it can bend and change shape without sudden breakage. This is super-balanced safety, would you say? Because if something is ductile, it bends before breaking. CNC machinists like this feature because they can make machined parts easily.
Thermal Properties of CNC Machining Materials:
Thermal Conductivity
Thermal conductivity is the ability of a material to conduct heat. Consider both a metal spoon and a wooden spoon inside of hot soup. You know how fast a metal spoon heats up?
Metal retains heat; thus, it has good thermal conductivity properties. It easily conducts heat. However, wood does not heat up as quickly. The thermal conductivity of it is small. In simple terms, thermal conductivity is how well heat passes through a material.
Importance
It depends on what you are making. For example, if you are creating cooking pots, you require high thermal conductivity so that the pot heats quickly and evenly. But if you are making handles for pots, you want it to conduct heat to your hand! Understand?
Note that in electronics, there are some times we need to dissipate the heat away from the components. Hence, we use high thermal conductive materials. Sometimes, as with in-house insulation, you want to retain heat or repel it. Thus, we employ low thermal conductor materials.
CNC Machining Materials Cost:
Let’s make it straightforward — how much will your material cost to purchase? Other materials such as steel — are very cheap. On the other hand, gold or titanium can be much more expensive. I mean, you agree that price is a huge factor when choosing what to make a project out of, right?
CNC Machining Materials and Their Approximate Costs
| Material | Approximate Cost (per kg) |
| Aluminum (6061) | $5-$15 |
| Stainless Steel (304) | $10-$30 |
| Brass | $8-$20 |
| Copper | $15-$40 |
| Titanium | $50-$100 |
| Steel (Mild) | $3-$8 |
| Acrylic | $5-$15 |
| ABS Plastic | $3-$8 |
| Carbon Fiber | $50-$200 |
| Inconel | $30-$70 |
Machining costs
In simple terms, machining costs are the costs of a complete finished product. Other materials like aluminum are more straightforward to cut and mould. Some are more difficult to machine, like super-hard steels.
It means that harder materials are more expensive to machine since they require more time and specialized tools. In essence, machining costs are based on the material’s machinability.
CNC Machining Costs to Machine Materials
| Material | Approximate Machining Cost (per hour) |
| Aluminum | $75-$200 |
| Stainless Steel | $125-$350 |
| Brass | $100-$250 |
| Copper | $150-$400 |
| Titanium | $250-$600 |
| Steel (Mild) | $50-$150 |
| Acrylic | $25-$100 |
| ABS Plastic | $25-$100 |
| Carbon Fiber | $100-$300 |
| Inconel | $200-$500 |
Project budget
The budget is the total cost of the entire CNC machining project. It is also relatively simple. It includes the cost of materials, machining, and labor and energy.
Always remember that you are constantly working with a budget when you are planning a project. For example, incorporate resources, materials, and processes that are within the budget. Alright?
Surface Finish:
What does surface finish mean in simple terms? The surface finish refers to how rough or smooth the surface is for any given object. A mirror surface finish is the smoothest finish available. A coarse grain of sandpaper creates a very rough surface finish. One can also describe it in terms of the number of microscopic bumps and grooves present on the surface.
Importance
So, why is the surface finish so important? Well, it’s crucial because it affects how a part looks and functions. It impacts the way assembled components fit together and wear, as well as their resistance to corrosion. For instance, smooth surface finishes in engines reduce friction and wear in rotating parts.
Standard CNC Machining Materials
Metals:
Aluminum:
Properties
Aluminium is a soft, lightweight metal. It excels at repelling rust, which is an added benefit. Additionally, it has good thermal conductivity, something you might already know. It’s also not very hard, making it machineable as well.
Common Alloys
Alloys of aluminum come in several forms. 6061 and 7075 are some of the more common alloys. These numbers simply indicate the particular alloy used in the aluminum, which slightly alters its properties.
Applications
Aluminium is a common metal found in a variety of items! For instance, it’s used in planes, cars, and bikes due to its lightweight nature. It’s also beneficial for electronic parts as it helps cool components down. Additionally, it is ideal for items that need to resist rust, like outdoor power tools.
Cons
Steel is stronger in general, which is a disadvantage of aluminum. It also can cost a bit more than steel at times too. It is also slightly whittling down than any harder metal.
Steel:
Properties
More simply explained, Carbon steel is just steel with carbon in it. It is sturdy and tougher than aluminum. And that makes it less expensive than many other metals.
Applications
The tools, machine components and structural parts are made using carbon steel. Bits that can be robust and cheap.
Cons
Left unprotected, carbon steel does corrode easily. It also is not as durable as other steel types.
Stainless Steel
Properties
In simpler terms, stainless steel is simply steel with chromium. This chromium is what helps keep it from rusting so easily, which is why it is so “stainless”! Because it is also durable and pretty shiny.
Common Grades
Typical grades are 304 and 316. Those numbers indicate the specific metal components that make up the stainless steel, and that affects how resistant it is to rust and how strong it is.
Applications
Stainless steel is a good option for kitchen items, medical parts and other items that need to be pure and rust-free. It is also a good option for areas that need to feel nice and durable.
Cons
When compared to carbon steel, stainless steel is expensive. And it may be more difficult to machine than aluminium.
Tool Steel
Properties
To put it mildly, tool steel is a special type of steel that is harder than regular hard steel and more durable than regular steel. It’s built to cut and stay lasting.
Applications
Cutting tools, molds, and dies are tools steel. Cutting edges and those that shape other materials.
Cons
Tool steel is brittle, so it can snap if you bend it too much. It is typically costlier and more challenging to machine than carbon steel.
Magnesium:
Properties
Magnesium is an extremely light metal. Its weight is even less than that of aluminum!
Aluminum Bronze:
Properties
In simplest terms, aluminium bronze is a blend of copper and aluminium. It is durable and does not wear and rust easily. And it even appears somewhat golden.
Applications
Aluminum bronze is used for bearings, gears and marine applications. These machined metal parts should be strong and resistant to wear and working in saline water.
Cast Iron:
Properties
Cast iron, in simpler terms, is iron with a high carbon content. It has a high compressive strength and retains heat well. It’s also cheap to make.
Applications
Examples of where cast iron is used include engine blocks, cookware (pans), and machine bases. This material is incorporated in heavy items that need to prevent vibration.
Silver Steel (High Carbon Steel)
Properties
Silver steel is a high-precision and high-carbon steel that is very hard. The bright polished surface is why it’s known as “silver steel.”
Applications
Its main applications and uses are precision tools, punches and pins.
Titanium:
Properties
Titanium is an exceptionally durable, lightweight, and corrosion-resistant metal. Its performance is exceptional in high temperatures.
Plastics:
For the most part, plastics weigh less, can be mass-produced, and are usually cheaper than metals. It can also be an excellent electrical and heat insulator.
Nylon:
Properties
Put simply, nylon is a durable and abrasion-resistant form of plastic. It also slides easily.
Applications
Nylon is employed in gears, bearings, and wear pads. It significantly resists wear & tear.
Acetal (Delrin)
Properties
Acetal is a hard, stiff plastic with some wear resistance and low friction. It also mixes well with chemicals.
Applications
CNC machining companies incorporate Derlin as a material for gears, bearings and electrical insulators. Not only is this a very strong material but also can perform in tough environmnetal conditions.
PEEK
Properties
In simple terms, PEEK is a special type of high-performance plastic. Moreover, it is extremely durable, heat-resistant, and resistant to chemical damage.
PTFE – Teflon:
Properties
PTFE/Teflon is an extremely slippery plastic. It has an extremely low coefficient of friction and is almost completely inert to chemicals and heat.
UHMWPE
Properties
UHMWPE is a high abrasion resistant, low friction plastic. It is incredibly resistant to impact as well.
PP
Properties
PP/polypropylene is cheap and a pervasive plastic. It’s flexible and chemical resistant.
Ertalyte
Properties
To put it another way, one kind of PET plastic is called Ertalyte. It is durable, has a high deflection limit, resists wear and is a ubiquitous CNC machining material.
What factors impact Machinability?
Our next topic of discussion is what makes a material easy or difficult to machine. This is called machinability. Herein lies the key to a few things that will really matter.
Material Hardness
We have already discussed this in more detail; you can explain how resistant a material is to scratching and denting. Let’s clarify further: the more complex the material, the more challenging it is to machine.
The harder the material, the more force and tougher tools a machining company will need to machine it. Ultimately, machine-hard materials will take longer and cost more.
Thermal Conductivity
You read this before. Thermal conductivity is the measure of a material’s ability to conduct heat. That is critical for machining because when metal is cut, it gets hot. Good thermal conductivity means that the material can remove heat from the cutting area.
This is a good thing since it helps to keep the tool and the workpiece cooler, which in turn makes it easier to machine and extends tool life.
When a material is not thermally conductive, the heat just stays there, which causes the material to gum up and melt. So, it leads to premature wear on your cutting tools.
Chemical Reactivity
Chemical reactivity is the tendency of a material to react with other materials, such as the cutting tool and air. While machining, some materials can react with the material of the cutting tool due to high temperatures. This results in losing the cutter quickly and making the material stick to the cutter.
In addition, some materials may be reactive with the coolant or lubricants used in machining. Therefore, chemical reactivity can make the entire machining process complicated. To control it, you will need to incorporate special coolants and tool coatings.
Work Hardening
Work hardening is the natural phenomenon of metal bending and forming. In machining, this factor is very important because, as you are cutting, the material you are instantly coming in contact with can become more difficult. So this hardened area will be very tough to cut with tools. It will lead to premature wear & tear of machining tools.
It is a well-known fact that hard machining materials are more difficult to machine.
Chip Formation
In the CNC machining process, milling and turning machines often cut away the material and create little pieces. Every machinist wants to control the chips easily. However, some CNC machining materials form long stringy chips that tangle around the tool. It can cause problems for tools. Materials with manageable chips are easy to machine.
Cost Comparison for CNC Machining Materials
Cost is an important factor in CNC machining materials. Some materials are expensive, while others are affordable. Aluminium and steel are examples. 6061 aluminium is a common choice because it’s a good, solid option for everything. It’s lightweight, very machinable, and fairly rust-resistant.
Steel, like carbon steel, is a stronger and more economical material for CNC machining.
Nevertheless, steel is denser and prone to rust, and certain steels are more challenging to machine, which can increase machining costs. If you require a lightweight, corrosion-resistant component, aluminum is a good option.
Even if the material cost is a little bit more than basic steel, but its performance is good.
Machining Costs
Machining costs play a significant role in selecting a material. This is a rough comparison of aluminium versus stainless steel machining. Generally, aluminium is cheaper to machine than stainless steel. Why is that? Aluminium is softer and has better thermal conductivity, which allows for quicker cutting and reduces tool wear!
Some grades of stainless steel are harder and tougher than others. It cuts slowly, and tool wear is also high. Admittedly, as a ballpark figure, some would say machining stainless steel may cost 2 to 3 times more than machining aluminum. And this is only for machining time and wear on the tools, not the material.
So you will see even if the cost of raw stainless steel material is not significantly higher than aluminum, the final cost of the part can be a lot more expensive due to machining.
Lead Times & Material Availability
Other than cost, availability of the material is also crcial. Take for example a common alloy — aluminum 6061 — or a carbon steel. These are super easy to find. They are typically available to order with a matter of days before delivery. This helps to ensure both short lead times and managing costs.
Now, you want to machine some PEEK plastic or titanium. These are less common. Ordering from specialty suppliers, longer lead times (weeks or even months). Higher lead time could sometimes result in a higher price if you require parts urgently.
Scrap Material Value
Scrap value can slightly reduce cost. Aluminium is known for its decent scrap value. Scrap aluminum prices today March 2 2025 in some markets are approximately $0.50 to $0.70 per pound. For common grades of steel, steel scrap tends to be lower (perhaps $0.10 to $0.20 per-pound less valuable).
Brass and copper scrap value more than aluminum scrap. If you are cutting a lot of material, and you are machining aluminum, you can actually have your cashback selling the scrap. This can help save money on your project, primarily for larger projects.
Case Study: CNC Machining Material for a Heat Sink
Lets take example of a company that wants to make the heat sinks for new computer chips. Engineers could choose aluminum or copper for this work. Copper is a more efficient thermal conductor than aluminum. However, copper is heavy and expensive as a material. Aluminum is inexpensive, and lighter than copper, and still comparatively effective at transferring heat.
So, what do they do? The engineers analyzed the project budget and the actual cooling required. Assuming the chips generated a lot of heat, and money wasn’t much of an issue, they’d choose copper for the best cooling.
But if the chips were left to get too hot, and they like to keep it cheap, then aluminum is the way to go. Aluminum is also easier to go with machining the heat sink shape so this also can save money on the machining process. So, with heat sinks, you see, it is an equation between how efficient it cools and how expensive it is.
Summary
Basically, your selection of CNC materials depend on the four factors: strength, hardness, heat, cost, and smoothness. You read that different metals and plastics have different pros and cons. Easy to machine materials saves money, and scrap value can help too. So it’s all about balancing what you need with what you can afford.
FAQs
What materials are used in CNC machining?
Aluminum, steel, brass, copper, titanium, and various plastics. Also compatible with wood, foam, and composites.
What are the raw materials for machining?
Metal stock (bars, sheets, tubes), plastic blocks, wood billets. These materials come as solid blanks in standard sizes.
Is CNC only for metal?
No – CNC can work with a lot of materials. These are plastics, wood, foam, composites, and wax. However, metal is common in machining metal parts.
What is the best plastic for CNC machining?
Delrin (POM) has good machinability and stability. ABS, acrylic, and HDPE are also good for machining.
What is the easiest metal to machine?
Aluminum is fastest to cut and easy to machine also. Moreover, tool wear is also very low. Brass and copper are also relatively easy compared to steel.
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