Short "Difference Between Cast Iron and Steel in CNC Machining"(6061 aluminum vs 7075 Cherry)

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When it comes to CNC (Computer Numerical Control) machining, the choice of materials plays a crucial role in achieving desired results. Two popular materials used in CNC machining are cast iron and steel. While both offer excellent properties for various applications, they differ in terms of composition, strength, and functionality. In this article, we will explore the differences between cast iron and steel materials in the context of CNC machining.

Cast iron is primarily composed of iron with carbon content ranging from 2% to 4%. It also contains traces of silicon, manganese, sulfur, and phosphorus. This composition makes cast iron strong, but brittle. On the other hand, steel consists mainly of iron and carbon, typically containing less than 2% carbon. The lesser carbon content enhances the toughness and malleability of steel.

Strength and Hardness:
Cast iron is known for its exceptional compressive strength, making it suitable for heavy-duty applications where resistance to wear and deformation are critical. Due to the high carbon content, cast iron exhibits excellent hardness, allowing it to withstand extreme loads without deforming. Meanwhile, steel offers a superior tensile strength, making it ideal for structures and components subjected to tension or bending forces. Although steel may not match cast iron's hardness, it provides better ductility, enabling it to handle more flexible applications.

In CNC machining, machinability refers to how easily a material can be cut, shaped, and finished using machine tools. When it comes to machinability, steel surpasses cast iron due to its lower brittleness. Steel can be drilled, milled, turned, or tapped with ease, providing precise outcomes. Conversely, cast iron's coarse grain structure presents challenges during machining as it tends to cause rapid tool wear and vibration. Specialized techniques such as annealing or using coated cutting tools may be necessary to overcome these challenges while working with cast iron.

Surface Finish:
The choice between cast iron and steel can significantly impact the surface finish of a machined component. Cast iron generally produces a rougher surface due to its high carbon content, which promotes formation of graphite flakes during solidification. Conversely, steel exhibits a smoother and more uniform surface finish as it lacks the presence of graphite. Depending on the application, either material can be chosen based on the desired surface qualities required for the final product.


Both cast iron and steel find diverse applications in CNC machining. Cast iron is commonly used in manufacturing engine blocks, machine bases, automotive parts, and structural components that require exceptional strength and wear resistance. Steel, on the other hand, finds uses in industries such as aerospace, automotive, construction, and tool manufacturing where properties like toughness, flexibility, and corrosion resistance are vital.

In summary, the differences between cast iron and steel materials in CNC machining lie in their composition, strength, hardness, machinability, surface finish, and applications. While cast iron boasts high compressive strength and hardness, it tends to be brittle and not as easily machined as steel. Steel offers enhanced tensile strength, better ductility, and improved machinability, making it suitable for various applications. Ultimately, understanding the unique characteristics of both materials allows CNC machining professionals to make informed decisions when choosing the most appropriate material for specific projects. CNC Milling CNC Machining