Brass is a non-ferrous metal commonly used in various industries for different purposes. From complex electronic connectors and durable plumbing fittings to high-performance automotive and aerospace components, brass is almost everywhere. Its ability to be machined with high accuracy makes it a top choice in manufacturing.
But how are these intricate brass parts produced with such precision and consistency? The answer lies in CNC machining, an automated process that shapes brass with remarkable accuracy and efficiency.
In this CNC machining brass guide, we’ll examine brass properties, various brass grades for custom parts, available finishes, and explore how to optimize the process for superior results.
What Is Brass CNC Machining?
Brass CNC machining is a subtractive manufacturing process that uses Computer Numerical Control (CNC) machines to precisely cut, shape, and drill brass workpieces by removing material. The material removal rate (MRR) depends on factors such as spindle speed, feed rate, and cutting tool choice. With proper parameter selection and rigid fixturing, CNC machining can achieve tolerances as tight as ±0.001".
Brass is an alloy of copper and zinc, and is one of the best CNC materials due to its high machinability and ductility. It also has good electrical and thermal conductivity, good corrosion resistance, antibacterial properties, and aesthetic appeal. Moreover, its mechanical properties can be adjusted by changing the proportions of copper, zinc, and trace elements such as tin, lead, or aluminum, enabling a wide range of hardness and toughness.
What Properties of Brass Make It Suitable for CNC Machining?
Next, let’s take an in-depth look at the key properties that make brass highly suitable for CNC machining:
Highly Machinable
Brass is one of the easiest metals to machine. Its relatively low hardness and excellent ductility reduce cutting forces and enable smooth chip formation, while the α+β dual phase microstructure naturally promotes chip breaking and evacuation. The alloy’s high thermal conductivity rapidly dissipates heat from the cutting zone, extending tool life.
In free cutting grades like C360, lead or sulfur additives further lower the friction coefficient, minimizing tool adhesion and wear. Together, these characteristics allow brass to be machined at cutting speeds and feed rates far higher than those used for steel and stainless steel, achieving higher material removal rates (MRR) while maintaining surface finish (Ra) and dimensional accuracy.
Corrosion Resistance
Brass is a non-ferrous copper-zinc alloy and therefore does not generate "rust" like iron-based metals. Its corrosion resistance primarily relies on a dense, naturally formed oxide or carbonate layer on the surface, which effectively blocks moisture and oxygen, protecting the underlying metal from further corrosion.
The alloy composition has a big impact on corrosion performance: Aluminum brass (such as C687) forms a stable aluminum oxide film on its surface, providing excellent resistance in seawater and various chemical environments. Conversely, brass with excessively high zinc content is more susceptible to dezincification in environments containing chlorides or sulfur compounds, leading to localized porosity and a reduction in mechanical strength.
Malleability
Malleability is a metal's ability to deform under compression or forming without cracking. Brass, with its high copper content, inherits the face‐centered cubic crystal structure of copper, resulting in excellent ductility. Low-zinc brass alloys (with zinc ≤ 35%) can achieve smooth, crack-free forming during deep drawing, bending, and stretching processes. However, as the zinc content increases, the alloy’s strength improves at the expense of some ductility. Additionally, cold working causes work hardening; to restore and further enhance ductility, annealing is typically carried out in the range of 400–650 °C to refine the grain structure and relieve stress, ensuring subsequent forming processes proceed smoothly.
Strength and Hardness
Although brass’s strength and hardness are often overlooked, they can be precisely controlled through alloying: increasing zinc content makes brass harder and stronger, while adding aluminum, tin, or nickel can further enhance its wear resistance and load bearing capacity. As a result, brass is well suited to both finely machined decorative parts and demanding structural components.
In CNC machining, standard brass grades can be machined efficiently and accurately with high speed steel (HSS) tools, whereas high strength or alloyed grades (such as C280, C464, and C687) benefit from carbide tooling to extend tool life and increase cutting speeds.
Aesthetic Appeal
Brass, with its wide range of color variations—including reddish gold, bright gold, and silvery white—is widely used in decorative items such as lighting fixtures, door handles, drawer pulls, and picture frames. The exact hue of brass depends on its copper to zinc ratio: higher copper content produces a warmer, reddish gold tone, while higher zinc levels yield a lighter, yellowish or silvery appearance.
Electrical and Thermal Conductivity
Brass typically has an electrical conductivity between 15–28% IACS (International Annealed Copper Standard), which is much lower than pure copper (100% IACS) but significantly higher than that of stainless or carbon steel. Its thermal conductivity generally ranges from about 100 to 125 W/m·K, roughly 25–30% that of pure copper (approximately 400 W/m·K). As the zinc content increases, both the electrical and thermal conductivities gradually decrease. When you need a material that balances decent conductivity with strength, corrosion resistance, and machinability, brass is the ideal compromise. This is why it’s widely used for electrical connectors, grounding components, heat exchangers, and HVAC valve bodies. In fact, nearly all Wire EDM electrode wires are made from brass.
Types of Brass Grades for CNC Machining
Below are some of the most common brass grades you’ll encounter in CNC shops, along with their key properties and typical uses:
C360 (Free-Cutting Brass)
C360 is the go to brass for general purpose CNC work, containing approximately 60–63 % copper (Cu), 34–37 % zinc (Zn), and 2.5-3.7% lead (Pb). The addition of lead improves chip breaking, reduces tool wear, and enables high speed machining.
Advantages:
Best machinability among all brass alloys (often rated at 100%)
Excellent dimensional accuracy and surface finish, suitable for high-precision components
Cost-effective for high-volume production due to excellent cutting efficiency
Disadvantages:
Limited strength under heavy loads or high temperatures
Prone to microcracks under cyclic loading and unsuitable for high-frequency reciprocating components
Poor resistance to dezincification in seawater or chloride-rich environments
Lead restricts its use in food and medical applications due to RoHS compliance issues
Applications:
Plumbing and valve fittings: ball valve cores, valve stems, connectors
Electrical connectors: terminals, bus bars, plug housings
Fasteners and decorative hardware: nuts, bolts, furniture fittings
C280 (Muntz Metal)
C280 contains roughly 60% copper, 40% zinc, and less than 0.07% iron. It typically has a distinctive architectural bronze color and can be easily polished to achieve a bright, reflective finish that enhances its appeal in decorative and structural applications.This grade of brass is stronger, harder, and more rigid than brass with lower zinc content, with machinability at around 40% (versus 100% for C36000).
Advantages:
Higher strength and hardness than C360
More resistance to abrasion and wear
Retain tight tolerances and stable dimensions even under load
Disadvantages:
Lower machinability than free cutting brasses and is more prone to work hardening during processing
Reduced ductility limits its suitability for processes requiring extensive forming or deep drawing
Applications:
Industrial and structural components: gears, shafts, valves, and bearing housings
Automotive components: radiator parts and heavy duty connectors
Architectural applications: decorative panels and elevator doors
C464 (Naval Brass)
C464 is a copper-zinc-tin alloy consisting of about 60% copper (Cu), 39% zinc (Zn), and 1% tin (Sn). The addition of tin improves its resistance to seawater corrosion and prevents dezincification, making it well-suited for marine environments. And its machinability is approximately 30% relative to C360.
Advantages:
Excellent resistance in seawater
Good strength ,wear and fatigue resistance
Disadvantages:
Lower machinability compared to free-cutting brass grades
Architectural and water treatment systems ：pipes, valves, fittings, and related equipment
Heat exchangers and cooling systems
Medical instrument connectors and housings
C687 (Aluminum Brass)
C687 is a copper–zinc–aluminum alloy typically composed of 76–79% Cu, 20–22% Zn, and 1.8–2.5% Al, plus a small arsenic addition (~0.03%) to inhibit dezincification. The aluminum content forms a dense oxide film on the alloy surface, delivering exceptional resistance to corrosion and erosion in high velocity or hot seawater.
Advantages:
Extremely resistant to high velocity seawater, salt spray, microbiological activity, and dezincification
Higher strength and hardness than low zinc brass, though slightly lower than C280
In the annealed condition, it can be cold rolled, drawn, or expanded to produce thin walled tubes
Disadvantages:
Its machinability is roughly 30 % that of C360
Lower electrical conductivity (~23% IACS) than other brasses
Applications:
Marine & Shipping: Condenser tubes, high speed seawater pumps, and firefighting water lines
Power Generation / Petrochemicals: Generator coolers, evaporators, and heat exchangers for cooling water
Seawater Desalination: Multi stage flash (MSF) or reverse osmosis (RO) preheater tubing
C260 (Cartridge Brass)
C260, also called "70/30" (70% Cu, 30% Zn), is a lead-free brass alloy with a classic, warm golden-yellow tone. Among brass alloys, C260 offers the highest ductility and can undergo deep drawing, stretching, and bending operations. Its excellent formability helps prevent cracking, making it a popular choice for producing complex-shaped pipes and decorative components.
Advantages:
Excellent ductility and cold formability
Resistant to corrosion from atmospheric exposure, water, and most mild chemical environments
Bright gold-like appearance, suitable for decorative finishes
Disadvantages:
Its machinability rating is only about 30% that of C360, and it tends to produce long, stringy chips that are prone to entanglement
Susceptible to dezincification and stress corrosion in ammonia or acidic environments
Relatively low strength in annealed state
Applications:
Deep-drawn and spun components：ammunition cartridge cases, lamp shells
Automotive radiators and heat exchanger tubes
Musical instrument brass, hinges, springs, rivets
Surface Finishes for CNC Machined Brass Parts
Machined brass typically has a natural golden surface, which can serve as a finish on its own. However, depending on your needs, additional surface finishes may be required. Below are some options for CNC machined brass.
As Machined
The as-machined finish for brass represents the surface directly from CNC machining, without any additional surface treatment. This finish may have machining marks or roughness, but it maintains the original dimensions and functionality without alteration. It is ideal for internal brass components or prototype parts where functionality and fast turnaround are prioritized over aesthetics. However, such parts are more likely to get damaged due to the lack of surface protection.
Polishing
Polishing, using mechanical or chemical and electrochemical methods, removes machining marks and surface irregularities from brass parts. This process creates a smooth, mirror-like finish that is especially desirable for decorative brass items like lighting fixtures, musical instruments, and furniture hardware.
A polished surface also reduces friction, resists dirt and moisture buildup, and helps prevent corrosion. Additionally, polishing reveals true dimensional accuracy of the part by eliminating minor surface distortions. However, over-polishing can cause dimensional changes or surface damage. Even after polishing, brass parts may tarnish over time, so applying a protective coating or sealant can help maintain the finish and extend the part's service life.
Powder Coating
Powder coating is a durable finishing process in which a dry polymer-based powder is applied electrostatically to the brass surface and then cured under heat. This creates a thick, uniform layer that's more resistant to chipping, scratching, and fading than conventional liquid paints. The coating completely encapsulates the brass, providing excellent barrier protection against moisture, chemicals, and UV radiation. Powder coating is available in a variety of colors and textures, allowing manufacturers to achieve different visual effects beyond the natural brass tone.
Electroplating
This process uses electrolysis to bind another metal’s molecules to the brass’s surface. The most common electroplating metals include nickel for corrosion and wear resistance, chrome for a shiny surface with high wear and corrosion resistance, gold for excellent conductivity, oxidation resistance, and high-end decoration, and silver for enhanced electrical performance and aesthetics.
Helpful Tips for Successful CNC Machining Brass
Brass tends to work-harden during machining, especially in continuous cuts, which may result in poor tool performance. Carbide tools are often preferred for their durability and ability to withstand the high cutting speeds typical of brass. For softer brass alloys (e.g., C260 Cartridge Brass), high-speed steel (HSS) tools can also be effective.
Brass allows for higher spindle speeds compared to steels and harder metals, reducing cycle time. Be sure to set spindle speed (RPM) and feed rate (IPM) appropriately for the specific brass alloy.
Use spindle liners and collets to support bar stock and minimize vibration, improving surface finish. Reduce clearance and use rigid setups to prevent bar whip, which can negatively impact precision.
For long, thin brass parts, consider using a tailstock or steady rest to enhance stability.
Proper programming is essential in CNC machining brass, for example, using the proper G-code to optimize toolpaths for brass cutting, reducing idle movements, and preventing tool wear from redundant passes.
Brass dissipates heat effectively, so coolant is often unnecessary in routine machining. In less demanding operations, coolant may even cause mess or oxidation. However, it is essential to use an appropriate coolant or lubricant in specific machining operations—such as deep drilling, high-speed cutting, or heavy cuts—to reduce friction, enhance tool life, and improve surface finish. Water-soluble coolants or light oils work well when cooling is required.
Conclusion
Brass is a highly machinable and cost-effective CNC metal, making it an excellent choice for precision CNC machining. By selecting the right brass grade, optimizing machining parameters, and applying the appropriate surface finishes, you can achieve high-quality, high-performance brass products.
With over ten years of manufacturing experience, Chiggo is a reliable CNC machining provider, and our service experts will assist you throughout your manufacturing process, guaranteeing precision, efficiency, and consistency. Chat with us to learn more about our CNC machining services.
FAQ
Is brass easier to machine than aluminum?
In general, many free-machining brass alloys are easier to machine than aluminum because brass tends to produce clean, controllable chips and causes less tool wear, whereas aluminum, despite its softness, can form built-up edges on the cutting tool, affecting the surface finish.However, the answer depends on the specific grade of brass and aluminum being compared, as well as the machining operation.
Why aluminum brass (C687) belongs to the brass family, not aluminum alloys?
C687 is classified as a brass alloy because it is copper-based (76-79% Cu), with zinc as the primary alloying element, while aluminum is only a minor additive (about 2%) to improve corrosion resistance, not the base metal. It shares mechanical properties, machinability, and industry classification with other brass alloys.
Additionally, C687 follows brass alloy standards (ASTM B111, UNS C68700) rather than aluminum alloy standards.
