How to Choose the Best CNC Machining Material

CNC machining is a rapid, efficient, accurate, and versatile manufacturing process. CNC machining is compatible with a variety of hard and soft engineering materials, including metals and plastics. The functionality of CNC machined parts largely depends on the materials used. Therefore, material selection is a crucial step that must be carefully undertaken in CNC machining.

In this article, we will explore the advantages and typical applications of commonly used metals in CNC machining, including aluminum alloys, stainless steel, low carbon steel, tool steel, copper, brass, and titanium alloys.

Aluminum Alloys

Aluminum alloys have several advantages in CNC machining, including an excellent strength-to-weight ratio, good machinability, high thermal and electrical conductivity, and corrosion resistance.

 Aluminum alloys are easy to machine and are very friendly for cutting and forming operations, making CNC machining of aluminum alloys highly efficient. CNC machining of aluminum alloys is often the most economical choice for producing prototypes and other types of parts. It can be mass-produced and is cost-effective.

Common aluminum alloys used in CNC machining

  • 5083 Aluminum Alloy: Compared to other aluminum alloys, 5083 aluminum has higher strength and good corrosion resistance, making it suitable for marine applications.
  • 6061 Aluminum Alloy: 6061 aluminum is the most common general-purpose aluminum alloy with good overall performance for various applications.
  • 6063 Aluminum Alloy: Used for structural profiles suitable for the construction and manufacturing industries.
  • 2024 Aluminum Alloy: Offers high strength and good machinability, often used for aircraft structural components.
  • 7075 Aluminum Alloy: 7075 aluminum alloy exhibits superior fatigue properties, high strength, and can be heat-treated to enhance its strength and hardness. It’s used for parts requiring extreme strength, such as aerospace applications.

Applications of Aluminum Alloy CNC Machining

  • Aerospace: Aluminum alloys are extensively used in aircraft structures and parts due to their ability to reduce the weight of the aircraft while providing good strength.
  • Automotive: Used in car engine parts, body structures, hubs, etc., to improve fuel efficiency and performance.
  • Electronics: Used for casings and heat sinks in electronic devices to maintain stable temperatures.
  • Marine: Aluminum alloys are a common choice in manufacturing ships and marine equipment due to their corrosion resistance.
  • Sports Equipment: Used in bicycles, motorcycles, and other sports equipment for lightweight and high-performance parts.

Stainless steel alloys exhibit excellent wear and corrosion resistance, along with high strength, ductility, and are easy to weld and machine. These outstanding characteristics make stainless steel a popular choice in CNC machining.

Commonly Used Stainless Steel Grades in CNC Machining

  • 304 Stainless Steel: The most commonly used stainless steel grade, resistant to most environmental conditions and corrosive media, suitable for most general applications.
  • 316 Stainless Steel: Mechanically similar to 304 but with enhanced corrosion and chemical resistance, commonly used in medical or marine applications.
  • 17-4 PH: A specially treated stainless steel with mechanical properties comparable to 304. 17-4PH offers excellent strength, hardness, and chemical resistance, typically used in aerospace and high-performance applications.
  • 2205 Duplex Stainless Steel: Boasting double the strength of regular stainless steel alloys and excellent corrosion resistance, it’s used in extreme environments, often found in the oil and gas industry.
  • Medical Instruments: Used for surgical instruments and other medical equipment due to its corrosion resistance and ease of disinfection.
  • Food Processing Equipment: As stainless steel does not chemically react with food and is easy to clean, it’s the ideal choice for food processing equipment.
  • Marine Hardware: Favored for marine applications due to its corrosion resistance.
  • Automotive Parts: Used for various durable and high-performance car parts.

Low Carbon Steel

Low carbon steel offers good mechanical properties, is easy to machine, and boasts superior weldability. Compared to other types of steel or metals, low carbon steel is generally more affordable, making it an ideal choice for budget-restricted projects. Although it has relatively lower hardness, low carbon steel has good toughness, resisting impacts and deformation.

Common Grades of Low Carbon Steel for CNC Machining

  • A36: The most commonly used low carbon steel grade with good weldability, suitable for most general applications, especially in the construction industry.
  • 1018: A general-purpose alloy, 1018 offers excellent machinability, weldability, toughness, strength, and hardness. It’s the most commonly used low carbon steel alloy.
  • 1020: A steel with a minimal carbon content, frequently used in automotive and mechanical applications.
  • 1045: A medium carbon steel, 1045 offers good machinability, weldability, higher strength, and impact resistance.

Applications of Low Carbon Steel CNC Machining

  • Construction Industry: Low carbon steel is frequently used for building structures, frames, and supports.
  • Automotive Industry: Due to its cost-effectiveness and toughness, low carbon steel is commonly used to manufacture car bodies and other components.
  • Piping Systems: The weldability of low carbon steel makes it an ideal choice for various pipes and pipe fittings.
  • Furniture Manufacturing: Low carbon steel is also used to manufacture various furniture and fixtures.

Alloy Steel

Alloy steel is a type of steel that has been specially treated and added with elements to enhance its mechanical properties. In addition to carbon, alloy steel also contains other alloying elements, enhancing its hardness, toughness, fatigue resistance, oxidation resistance, and wear resistance.

Commonly Used Grades of Alloy Steel in CNC Machining

  • 4140 Alloy Steel: A very common medium carbon alloy steel with good overall mechanical properties, offering good strength and toughness. 4140 is used to manufacture bearings and other high-stress components.
  • 4340 Alloy Steel: This alloy steel has superior strength, toughness, wear resistance, and fatigue strength. 4340 can achieve high levels of strength and hardness through heat treatment, often used in aerospace applications.
  • 8620 Alloy Steel: A low carbon nickel-chromium-molybdenum alloy steel suitable for manufacturing gears and bearings.
  • O1 Tool Steel: A high carbon alloy tool steel with good machinability and wear resistance, typically used for cutting tools and molds.

Applications of Alloy Steel CNC Machining

  • Aerospace: Alloy steel is frequently used to manufacture aircraft engines and other key components.
  • Automotive Industry: Used for manufacturing high-performance auto parts, such as gears and shafts.
  • Energy Industry: In the oil and gas sector, alloy steel is used to manufacture various equipment that can withstand high pressures and temperatures.
  • Mechanical Manufacturing: Alloy steel has extensive applications in producing various industrial machinery and equipment.

Tool Steel

Tool steel is a metal alloy that, when heat-treated, has an extremely high hardness, enabling it to withstand substantial wear and tear. Tool steel has excellent wear resistance, resulting in relatively low wear during the machining process. Although the initial purchase cost of tool steel may be higher, its durability and reliability make it very cost-effective in the long run.

Common Grades of Tool Steel in CNC Machining

  • D2 Tool Steel: Tool steel D2 is a wear-resistant alloy. It retains its hardness even at temperatures of up to 425°C (797°F) and is typically used for making cutting tools and molds.
  • A2 Tool Steel: A2 is an air-hardening general-purpose tool steel with high compressive strength and good hardness. A2 tool steel can maintain excellent dimensional stability at high temperatures. It’s commonly used for injection molds.
  • O1 Tool Steel: O1 is an oil-hardening alloy with good depth of hardening and wear resistance. Its hardness can reach up to 65 HRC. It’s typically used for cutting tools.
  • H13 Tool Steel: Offers good thermal strength and wear resistance.
  • S7 Tool Steel: Known for its impact toughness and stability.

Applications of Tool Steel CNC Machining

  • Mold Manufacturing: Including injection molds, die-casting molds, etc.
  • Metal Cutting: Such as milling, turning, etc.
  • Aerospace: Used for manufacturing high-precision and complex parts.
  • Automotive Industry: Manufacturing various durable auto parts.
  • Medical Equipment: Such as surgical blades, forceps, etc.
  • Mechanical Processing: Manufacturing high-precision parts for various industrial applications.


Brass is a metal alloy known for its excellent machinability. It’s very easy to cut and mill, which significantly reduces machining time. Brass also has good surface finish and bendability, qualities highly beneficial for CNC machining. Additionally, brass has excellent electrical conductivity and is often used for electronic and electrical applications.

Common Grades of Brass for CNC Machining

  • C36000: Also known as “Free-Cutting Brass”, it’s a material with high tensile strength and natural corrosion resistance. Its superior machinability makes it ideal for large-scale applications.
  • C26000: Good machinability and formability, used for tubing and connectors.
  • C46400: Naval brass, known for its corrosion resistance.
  • C22000: Medium-hard brass used for general engineering applications.
  • C23000: Red brass, recognized for its electrical conductivity and corrosion resistance.

Common Fields of Brass CNC Machining

  • Electronics: Examples include connectors, sockets, etc.
  • Pipes and Valves: Commonly seen in water treatment and supply systems.
  • Decorative Items: Such as furniture, light fixtures, and artworks.
  • Instrument Manufacturing: Including measuring instruments and precision components.
  • Automotive Industry: Used to manufacture electronic components and decorations.

Titanium Alloy

Titanium is renowned for its high strength, lightweight, toughness, thermal stability, corrosion resistance, and fatigue resistance. It is typically used to manufacture the most demanding aerospace and military components. Titanium alloy also exhibits biocompatibility, making it suitable for medical device manufacturing.

Commonly Used Grades of Titanium in CNC Machining

  • Ti-6Al-4V (Grade 5): The most commonly used titanium alloy, possessing high strength and good mechanical properties.
  • Ti-6Al-7Nb: Often used in medical applications due to its excellent biocompatibility.
  • Ti-3Al-2.5V (Grade 9): Lightweight with high strength, commonly used in aerospace and bicycle frames.
  • Commercially Pure (CP) Titanium: Pure titanium used in applications where good corrosion resistance is required but high strength isn’t essential.
  • Ti-5553: A high-strength titanium alloy used in aerospace applications.

Applications of Titanium CNC Machining

  • Aerospace: For manufacturing aircraft structural components, engine parts, etc.
  • Medical Devices: Examples include artificial joints, dental implants, and surgical instruments.
  • High-Performance Vehicles: Such as engines and suspension systems of racing cars and high-performance vehicles.
  • Marine Applications: Used for producing submarines and marine structures.
  • Energy Industry: Such as drill bits used in the exploration of oil and natural gas.

Key Considerations in Selecting CNC Machining Materials

Final Use of the Component

The end use and location of a component are among the most crucial considerations when choosing CNC manufacturing materials. Different applications necessitate different materials. For instance:

  • Both stainless steel and carbon steel are suitable for CNC machining, but only stainless steel is naturally corrosion-resistant.
  • Heavier metals can withstand more stress, but for weight-sensitive applications, a lighter material with a good strength-to-weight ratio is essential. Compared to building structural support components, parts produced for aerospace applications need to be lightweight. Aluminum alloy, with its good strength-to-weight ratio, is often used in the aerospace industry.

Whether the Component Requires High Strength

A metal’s strength can be measured in various ways, including tensile strength, wear resistance, toughness, and compression. Engineers, when designing components, must consider the strength of the product. The strength requirements of a product will influence the final metal material selection.

Whether the Component Requires Heat Resistance

If a component’s operating temperature is too high, some materials have to be eliminated from the start. Almost all materials will expand or contract with temperature changes. If a component undergoes multiple heating and cooling cycles, materials that remain thermally stable at temperatures far above expected operating conditions should be chosen. This prevents critical component failures.

Project Budget

CNC machining produces a lot of waste material during the process. In situations where some metals are expensive, the cost of materials becomes very significant. To reduce the budget of the project, the various properties of materials must be carefully considered when making a selection. The ultimate goal is to find a suitable, cost-effective metal material.

At Manek Casting, we can provide CNC machining services, including CNC milling and turning, and CNC machining a variety of materials, from popular metals to high-quality plastics.

Our advanced equipment and experienced team enable us to provide our customers with unparalleled precision and quality. Whether you need custom CNC machined parts or have a specific project, we’re here to help you every step of the way.


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