In CNC machining material selection for projects is crucial to ensuring excellent performance and longevity. In this article we will address the most common considerations to assist in the material selection process.

CNC Material Selection Guidelines

When selecting materials for CNC machining a number of critical factors need to be addressed:

Part Application: How will the finished product be used?
Operating Environment: What conditions will the part endure?
Material Stress Load: What stress loads will the part need to withstand?
Dimensional Tolerance: How accurately can the material be machined?
Machinability: How difficult is it to machine the material?
Appearance Suitability: Does the material meet aesthetic requirements?
Material Cost Implications: Is the material affordable within the project budget?

These guidelines ensure the best performance and durability of machined parts. Carefully evaluating these factors leads to informed decisions and high-quality finished products.

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Part Application

Selecting the right material depends on the intended application and specific performance requirements. For components bearing heavy loads, materials with high strength and durability, such as steel or titanium, are necessary. If weight is a critical factor, like in aerospace applications, aluminium or magnesium is more beneficial.

For aesthetic parts with lower mechanical demands, plastics or softer metals like brass might suffice. Consider wear resistance if the part will move against other components. Each material offers unique properties, so aligning material choice with the part's function is essential.

Operating Environment

Consider the operating environment to guarantee peak performance and longevity of machined parts.

Temperature: Ensure the material withstands temperature fluctuations.

Moisture: Choose corrosion-resistant materials for humid environments.

Chemical Exposure: Select materials that endure specific chemicals.

Physical Stress: Determine if the material can handle vibration or impact.

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Dimensional Tolerance

Dimensional tolerance determines how accurately the machine can replicate the specified measurements of the part. The tighter the tolerance, the higher the precision. However, not all materials can hold tight tolerances as some can warp, shrink, or expand due to factors like temperature, causing deviations from desired measurements.

Dimensional Stability: Assess the material's stability under varying conditions.

Tight Tolerances: Ensure the material maintains tight tolerances throughout machining.

Thermal Expansion: Consider materials with low coefficients of thermal expansion to minimise dimensional changes.

Repeatability and Accuracy: Choose materials that offer high repeatability and accuracy.

Material Stress Load

Material stress load refers to the force a material can withstand before deformation or failure. Understanding the stress load requirements is vital since materials vary greatly in their ability to withstand stress.

Factors like part design, forces it will face, and operating conditions determine the needed material stress load. Choosing the correct material can mean the difference between a part that performs well and one that fails prematurely.

Consider tensile and compressive strengths, as well as impact resistance. Materials like steel and titanium offer high tensile strength, while denser materials like stainless steel or cast iron are better for parts under compression.

Materials like certain plastics or aluminium alloys provide good toughness for parts likely to experience impacts, ensuring longevity.


Machinability defines how easily a material can be cut, shaped, or finished using CNC machining tools. Materials like aluminium or brass offer excellent machinability, ensuring efficient production without compromising quality. These materials are easy to machine and cost-effective due to lower tool wear and quicker machining times.

Harder materials like stainless steel, titanium or inconel might slow the process and increase tool wear, raising project costs. Selecting materials with good machinability streamlines production and improves overall efficiency.

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Material Cost Implications

Materials vary widely in price based on their properties and availability. Some materials have higher upfront costs but save money in the long run due to durability and longevity.

Conversely, cheaper materials that don't meet project needs might result in frequent replacements or additional processing, increasing overall expenses.

Balance performance requirements and cost efficiency. Discuss your requirements with our team at A&M to receive advice on material choices that align with your project goals.

Appearance Suitability

The aesthetics of the final product can be as vital as its functionality, especially in consumer-facing applications.

Finish Options: Choose materials that offer a wide range of finish options for specific looks.

Colour Variety: Consider inherent colour variations for certain parts.

Surface Texture: Assess the natural surface texture of materials.

Coating Compatibility: Ensure the material is suitable for coatings like painting, anodizing, or powder coating.

The colour, texture, and finish of the chosen material impact the overall aesthetic of a project. For outdoor items, select materials that don’t discolour or degrade under weather conditions. For frequently handled products, choose materials with a pleasant tactile feel. Ultimately, the visual appeal of a product can be crucial when both aesthetics and function are important.

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Common Materials for CNC Machining

When choosing materials for CNC machining, consider both metal and plastic options. Each material type offers distinct properties that can influence the performance and durability of manufactured parts.

Metal CNC Materials

Common metal materials include aluminium, steel, stainless steel, titanium, and copper. Each metal has unique properties ideal for different applications, such as strength, corrosion resistance, and cost.

Aluminium: Known for its lightweight and strength, aluminium is highly resistant to corrosion and offers excellent thermal and electrical conductivity. It's ideal for aerospace and automotive parts, easy to machine, and can be anodized for extra durability.

Steel: Durable and strong, steel is popular in heavy industries like automotive and construction. It offers excellent machinability, handles high stress and wear, and is cost-effective, making it ideal for budget-conscious projects.

Stainless Steel: Offers remarkable corrosion resistance and durability, ideal for parts in harsh environments or requiring a clean, aesthetic finish. It's a top choice for medical, food processing, and marine applications.

Titanium: Known for its exceptional strength-to-weight ratio and biocompatibility, titanium is ideal for aerospace, medical, and automotive industries. It resists corrosion and high temperatures but is challenging to machine.

Copper: With excellent thermal and electrical conductivity, copper is ideal for electrical components and heat exchangers. It's malleable, corrosion-resistant, and essential for high-conductivity applications.

Inconel: Inconel is an exotic metal that is often used in the creation of parts within the aerospace industry. Often this material can damage traditional cutting tools but at A&M we have developed machining techniques to make adaptable changes to the cutting tips to overcome this issue.

Plastic CNC Materials

Plastic materials like acrylic, polypropylene, polycarbonate, ABS, and acetal offer distinct advantages in CNC machining. Each has unique properties that might suit specific project needs.

Acrylic: Known for clarity and versatility, acrylic is ideal for transparent components like lenses and light guides. It's highly resistant to weathering and UV light, ensuring durability for outdoor applications.

Polypropylene: Versatile and cost-effective, polypropylene excels in durability and chemical resistance, ideal for automotive and consumer goods. It's less prone to breaking under stress, making it reliable for functional prototypes and end-use parts.

Polycarbonate: Exceptional clarity and impact resistance make polycarbonate ideal for projects requiring transparency and strength, such as protective covers and lenses. It withstands high temperatures, suitable for various industrial applications.

ABS: Durable and easy to machine, ABS is shock-resistant, making it perfect for items that need to withstand heavy use. It's cost-effective, ideal for high-volume production, and suitable for automotive components and consumer electronics.

Acetal: Known for strength and stiffness, acetal is ideal for parts needing toughness and rigidity. It resists moisture and solvents, offering durability in challenging environments and excellent dimensional stability.

Nylon: Versatile with exceptional strength and thermal resistance, nylon is ideal for high-friction applications. It's resistant to wear and abrasion, ensuring durability, and absorbs minimal moisture, preventing warping.


Choosing the right material is essential for CNC machining projects. Each material comes with unique benefits and challenges, so identifying project requirements is crucial. At A&M, we offer expert guidance to assist with material selection. With the right choice, you'll enhance both the performance and longevity of your CNC machined parts.

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