Metal CNC machining has become a go-to method for producing both prototype parts and final components across many industries. Manufacturers rely on this process whenever they need consistent precision, repeatable quality, and efficient production times.
In this article, we will explain what metal CNC machining involves, explore the most common materials, discuss the factors you should weigh when choosing a metal. By the end, you will understand how to select the right material and machining approach to suit your project’s needs.
Metal CNC machining refers to the process of removing material from a metal workpiece using computer-controlled cutting tools. A machine reads a digital design created in CAD (Computer-Aided Design) software and follows precise toolpaths programmed in CAM (Computer-Aided Manufacturing) software. The machine moves the workpiece and cutting tool along multiple axes—usually three, but sometimes five—to carve the metal into the desired shape.
l CNC stands for “Computer Numerical Control.” That means a computer dictates the motion of the tools, ensuring accuracy and repeatability.
l Machining means “removing material.” In contrast to additive methods like 3D printing, CNC machining cuts away excess material to create parts.
l Metal describes the workpiece. Common metals include aluminum, steel, brass, and titanium.
Every metal brings its own combination of strength, machinability, weight, cost, and finish characteristics. Engineers and designers must balance these properties against final part requirements such as load-bearing capacity, environmental exposure, aesthetic needs, and budget constraints. Choosing the right metal at the outset can shorten lead times, lower costs, and improve product performance.
Selecting the right metal starts with understanding each material’s properties, costs, and typical applications. Below we summarize seven popular metals used in CNC machining.
Aluminum stands out as one of the most versatile and cost-effective choices for CNC machining. It appeals to designers who need a lightweight material without sacrificing strength. A typical part made from aluminum shows excellent dimensional stability and requires relatively low cutting forces, which speeds up production and minimizes tool wear.
l 6061-T6 Aluminum: Engineers favor the 6061-T6 grade for its balanced mix of strength, corrosion resistance, and affordability. Companies often use it to make aerospace brackets, automotive parts, and outdoor equipment.
l 7075-T6 Aluminum: This alloy offers higher tensile strength than 6061-T6, making it suitable for applications in aerospace structures and high-performance sporting goods. However, shops flag it as slightly more challenging to machine.
BOYI TECHNOLOGY’s aluminum CNC milling service supports a variety of aluminum alloys (e.g., 6061-T6, 7075, 6082) to meet diverse strength, corrosion-resistance, and aesthetic requirements.
Stainless steel remains a top pick when corrosion resistance and overall durability outweigh machining speed. Its higher cutting forces lead to slower feed rates and more robust tooling, but the trade-off delivers parts that withstand harsh chemicals and high temperatures.
l 304 Stainless Steel: Manufacturers often select 304H and 304L grades for kitchen equipment, food processing machinery, and architectural components. These grades balance formability with good weldability.
l 316 Stainless Steel: The 316 family adds molybdenum to improve resistance to chlorides and acidic environments. Medical instruments and marine hardware frequently use this grade.
l 303 Stainless Steel: Machinists recommend 303 for complex parts because its sulfur-enhanced composition boosts machinability, although it sacrifices some corrosion resistance compared to 304.
Carbon steel alloys combine high tensile strength with excellent ductility and weldability. Shops often use carbon steel when strength and toughness outweigh concerns about surface finish or corrosion resistance.
l AISI 1018: This low-carbon steel machines cleanly and welds easily, making it ideal for shafts, pins, and general-purpose hardware.
l AISI 4140: Engineers gravitate toward 4140 when they need a heat-treatable alloy with superior fatigue resistance, such as in gears, crankshafts, and heavy machinery components.
As an alloy of copper and zinc, brass offers good machinability, moderate strength, and an attractive golden color. Manufacturers use brass for plumbing fittings, decorative hardware, and musical instruments. Its natural corrosion resistance in salt-water environments also makes it a choice material for marine applications.
Pure copper excels in thermal and electrical conductivity. Machinists appreciate its ductility and ease of forming. Industries rely on copper parts for heat exchangers, electrical connectors, and semiconductor manufacturing equipment.
Titanium combines a remarkable strength-to-weight ratio with outstanding corrosion resistance. Medical device manufacturers and aerospace firms prize it for implants, airframe components, and engine parts. Shops note that titanium’s hardness and tendency to work-harden drive up cutting forces, so they use specialized tooling and lower spindle speeds to achieve smooth finishes.
Magnesium claims the title of the lightest structural metal in commercial use. Its density clocks in at roughly two-thirds that of aluminum, making it ideal for automotive frames, aerospace components, and handheld electronics where every gram counts. However, machinists exercise caution because magnesium can ignite under improper cutting conditions.
Choosing the right metal for your CNC project depends on several considerations beyond basic machinability and cost.
You should match the metal’s strength, stiffness, and fatigue resistance to how the part will perform in service. For high-load applications, steels or titanium alloys might suit best. For low-stress housings or cosmetic elements, aluminum or brass can work.
If your part will operate outdoors, near saltwater, or in corrosive chemicals, prioritize stainless steel or titanium. For indoor electronics, copper’s conductivity can make it the obvious choice.
You must balance cycle time against the raw material cost. Although titanium costs more per pound, its lower density may reduce part weight enough to justify the expense. Conversely, aluminum often yields the fastest cycle times, reducing overall cost.
Consider whether your part needs extra finishing like anodizing, plating, or polishing. Some metals, such as aluminum, accept anodizing readily. Harder steels can require grinding or tumbling to remove tooling marks, adding time and expense.
Applications like aerospace, medical implants, and drones demand very light parts. Magnesium or titanium may serve such needs better than heavier steels.
AT-Machining and similar shops maintain a range of CNC equipment to meet diverse project requirements. Below is an overview of common machine types:
A lathe spins the workpiece while a stationary cutting tool removes material. The process yields cylindrical parts such as shafts, bushings, and threaded rods.
In a 3-axis mill, the cutting tool moves along X, Y, and Z axes. This configuration handles most prismatic shapes, pockets, and simple contours. It remains the most economical setup for straightforward parts.
Mill-turn machines integrate a rotating spindle and milling heads. They let you perform turning and milling in one setup, reducing cycle time and eliminating errors from multiple fixturing steps.
A true 5-axis machine moves both the table and spindle across five independent axes. You can tilt and rotate the part to reach hidden features in a single run. While costly, these machines shine in aerospace, medical, and molds because they minimize manual repositioning.
Here we compare the primary machining operations your part may require:
l Provide Clear CAD Models: Ensure your 3D files include solid, manifold geometries.
l Specify Tolerances Wisely: Assign tight tolerances only where necessary. Overly precise specs increase cost.
l Choose Appropriate Surface Finish: Call out finishes such as Ra values or coatings like anodizing and plating.
l Discuss Material Certificates: Ask your supplier to provide mill test reports (MTRs) for traceability.
l Plan for Fixturing: Complex parts may require custom fixtures. Early planning avoids delays.
l Communicate Post-Processing Needs: If you need deburring, heat treat, or inspection (e.g., CMM reports), factor these into lead time and budget.
Choose BOYI TECHNOLOGY immediately. We have advanced equipment and a professional team, and are capable of meeting the demands of various metal and plastic parts quickly and efficiently. Whether it is a single prototype or mass production, we can offer competitive quotations and full technical support throughout the process. Contact our sales team immediately for exclusive solutions and quotations: [email protected].
Metal CNC machining offers unparalleled precision, repeatability, and flexibility for parts ranging from simple brackets to complex aerospace components. By understanding each material’s properties, weighing mechanical and environmental requirements, and selecting the right machine and process, you can optimize costs and performance. Communicate your part’s function, tolerances, and finish needs clearly with your machining partner, and you will benefit from faster cycles and fewer revisions.
Q: How much does metal CNC machining cost?
A: Aluminum parts with simple geometry in moderate volumes can cost as little as $20–$50 each, while high-precision titanium or stainless steel aerospace components can range into the hundreds or thousands of dollars per piece.
Q: Can I get prototypes and production parts from the same supplier?
A: Yes. Many CNC suppliers offer rapid prototyping services using the same equipment and processes as production runs. This continuity ensures consistency from initial proof-of-concept samples through large-scale manufacturing.
Q: How do I shorten lead times?
A: Designers can shorten lead times by selecting highly machinable metals (e.g., aluminum 6061-T6 or brass), simplifying part geometry, and minimizing the number of setups. Providing complete drawings and promptly answering technical queries also speeds up the quoting and programming stages.
Q: Is there a minimum order quantity?
A: Some precision shops have minimums as low as one piece; others may set batch runs at ten or more, depending on material handling and setup costs.
