One of the longest-standing material choice debates in CNC machining is the brass vs copper discussion, especially for precision CNC components. Although they belong to the same metal family and may share a similar appearance, brass and copper behave very differently during machining.
The difference in their machining performance is a direct result of the differences in their mechanical and machining properties. Their machining performance, in turn, affects the quality of the project, cycle time, and ultimately project cost. Understanding these mechanical differences between brass and copper is necessary for engineers and CNC project managers willing to make informed and balanced manufacturing decisions.
This article considers the brass vs copper debate from a CNC machining perspective, informing readers on their distinct properties and how these properties translate into real-world manufacturing decisions.
Brass vs Copper: What Are the Differences in CNC Machining?
The most basic difference between brass and copper is their composition. Copper is a pure element, while brass is an alloy of copper and zinc. This difference in composition cascades into differences in CNC machining outcomes.
Below are CNC-relevant areas where brass and copper differ, and the real-life implications of these differences.
Mechanical Properties
In the brass vs copper comparison for CNC machining, mechanical properties directly influence machining behavior and part performance. Brass and copper have different mechanical properties, and these differences are responsible for their specific machining properties and real life outcomes.
- Hardness: Brass hardness (3 to 4 on Mohs scale) is around 25 to 30% higher than copper (2.5 to 3 on Mohs scale).
- Strength: Brass (100 to 400 MPa) has a higher yield strength than copper (70-150 MPa). Similarly, brass (300 to 550 MPa) has higher tensile strength than copper (200 to 350 MPa).
- Elongation: Copper (maximum ~60%) is significantly more ductile than brass (max. ~40%).
| Property | Brass | Copper |
| Tensile strength (MPa) | 300 to 550 | 200 to 350 |
| Yield strength (MPa) | 100 to 400 | 70-150 |
| Elongation | ~60% | ~40% |
| Hardness (Mohs) | 3 to 4 | 2.5 to 3 |
Machining Properties
In the brass vs copper comparison, the differences in mechanical properties directly influence machining behaviors, including chip formation, tool wear, and tolerance stability, during CNC operations.
- Chip formation: During CNC operations, like milling and turning, brass produces short and brittle chips that break off cleanly and are easy to evacuate. However, due to its softness, copper produces long, continuous, and gummy chips that are difficult to control and evacuate. This reduces machining efficiency and increases cycle time.
- Tool wear: The gummy chips produced in copper machining stick to the cutting tool, causing Built-Up Edge (BUE) that accelerates tool wear and lowers surface quality. Copper’s high ductility causes material adhesion and BUE, which complicates chip evacuation and affects surface finish. In contrast, tool wear in brass machining is mainly due to abrasion. However, the adhesive wear mechanism in copper is typically more aggressive than the abrasive wear in brass. Therefore, despite being harder, brass generally exhibits less tool wear than copper. Additionally, brass often contains lead, which acts as a lubricant during cutting and further reduces tool wear.
- Tolerance capability: Being softer, copper is far more prone to deformation during machining. Copper also requires higher cutting speeds, and its high ductility can lead to accelerated tool wear or material smearing if not properly managed. This increases the chances of dimensional inaccuracies and limits its ability to hold tight tolerances.
Brass, however, is harder and more resistant to deformation during machining. Consequently, brass parts have better tolerance stability than copper parts.
Brass (80 to 100 rating) is significantly more machinable than copper (20 to 40 rating). The gap in machinability is largely due to the gumminess associated with copper chips, despite brass being the harder metal.
In brass vs copper machining comparisons, brass generally allows faster cycle times, more predictable tool life, and more stable dimensional outcomes. On the other hand, copper machining is longer and more effort-intensive as it requires more intensive monitoring and the need for specialized machining equipment.
Surface Finishing
In brass vs copper surface finishing outcomes, chip behavior and material rigidity play critical roles. There are two aspects to surface finishing in copper vs brass discussions: finish directly off the CNC machine and secondary finishing techniques.
Machined surface finishing:
Brass frequently produces a smooth surface finish directly off the machine, due to the manner its chips are produced. The chips in brass machining are short, discontinuous, and they break cleanly off.
These chips do not damage the surface quality of the finished brass part. Additionally, brass is rigid, meaning the workpiece is stable during cutting, and this is seen as smooth surface finishing in brass turned parts.
Meanwhile, copper is far more prone to bad surface quality off the machine, due to its softness, which increases the risk of surface smearing during cutting. The final product may then have a duller surface than desired.
Secondary surface finishing:
Post-processing surface finishing techniques, such as polishing, plating, and coating, can be applied to both brass and copper. Unlike copper, brass typically comes off the machine with already-decent surface quality and tight tolerances, so it does not commonly require secondary surface finishing for purely aesthetic reasons.
However, processes like passivation may be necessary to improve brass’s corrosion resistance. This is standard for components that will face aggressive moisture conditions, especially in the marine industry.
Copper often needs additional surface finishing operations to meet certain functional or aesthetic demands compared to brass. When applying any secondary surface finishing on copper parts, particularly electricals, it is crucial to keep oxidation control in mind, as the additional surface film may interfere with their normal function.
Conductivity
Conductivity can be assessed in either electrical or thermal terms. Here is the difference between brass and copper in this area.
- Electrical conductivity: Copper (100% IACS) is 3 to 4 times more conductive than brass (20 to 30% IACS). Electrical conductivity is arguably the most obvious difference in the brass vs copper debate, with copper being the industry standard across all metals.
While custom brass parts can still conduct electricity, many engineers remain unconvinced about using brass for their electrical projects. In reality, brass is conductive enough for projects that aren’t heavily dependent on efficiency and high conductivity. So, connectors, terminals, and grounding components can still be machined using brass.
- Thermal Conductivity: Copper (398 to 403 W/m·K) also has a significantly higher thermal conductivity than brass (115 to 160 W/m·K). This higher thermal conductivity means copper is better at drawing heat away from the cutting tools and zone during machining, lowering the risk of overheating. Brass is not as heat-conductive, implying that the risk of heat buildup in the cutting zone is higher.
At the end of the day, engineers must aim for a balance between conductivity and machinability in custom CNC parts. For projects that demand high conductivity, copper will almost always be better compared to brass, despite its lower machinability. Although copper has high thermal conductivity and dissipates heat efficiently, its ductility still promotes material adhesion at the cutting edge, which can accelerate tool wear through built-up edge formation.
However, copper’s efficiency at drawing heat away from the cutting zone can also be a problem because the metal itself is soft, and cutting tools may have built-up edges (BUE). Brass does not have this sticking problem, so the cutting tool integrity does not take any significant damage despite the increased heat generation.
Corrosion Resistance
Both copper and brass components have good corrosion resistance traits, but they behave differently depending on the environment. When exposed to the atmosphere, copper forms a patina of copper carbonate, which protects the underlying metal.
The copper patina can be functionally and even aesthetically desired. However, copper’s corrosion resistance starts to fail in harsh pH conditions, acidic or alkaline.
Brass also develops a patina in atmospheric conditions, as well as resists corrosion much better than copper in freshwater and weakly acidic or alkaline conditions. However, brass may experience dezincification in high-chloride environments, such as saltwater, leaving a weak copper base. This is a significant factor in brass vs bronze debates.
Applications
Brass and copper are both extremely common metals for CNC machining. However, they both have their areas of specialization. Brass is the preferred option for custom metal parts where machinability, strength, and good as-machined surface finish are critical. Copper machined parts are generally reserved for components that require excellent electrical and thermal conductivity.
Common CNC Brass Parts
- Valves
- Precision parts
- Musical instruments, such as trumpets
- Decorative parts, such as door handles
- Electricals, including connectors and terminals
Common CNC Copper Parts
- Electricals
- Radiators
- Surgical equipment
- Heat sinks
Design Considerations When Machining Brass vs Copper
There are certain design considerations that are necessary before making a manufacturing or buying decision between brass and copper for your project.
Minimum Wall Thickness
Generally, brass (~0.5 mm) can handle thinner walls, machining better than copper (0.8 to 1 mm). This is because brass has a higher tensile strength, while copper is softer and is more likely to bend or smear. Nonetheless, having too thin walls can still cause significant distortion even with brass due to high springback.
Threading Performance
Brass is more durable and cuts more cleanly than copper, which often correlates to better threads.
On the other hand, copper threads are significantly more susceptible to burrs and tearing.
Clamping Deformation Risks
Copper is soft and requires extra care when clamping to maintain dimensional accuracy. This is unlike brass, which is harder and more rigid, allowing it to withstand higher clamping forces without any deformation.
Recommended Alloys
Free-machining brass (C360) is often the benchmark for CNC brass machining projects. For copper machining, oxygen-free copper is often regarded as the best option.
Brass vs Copper: Cost and Production Considerations
One of the most important influential factors on what material a CNC project adopts is the cost involved in the project, and this is not just limited to the raw materials. Beyond the cost, the actual production process also plays a key role in making a decision.
Raw Material Cost Comparison
Copper raw material prices are generally higher than brass because of higher copper content and purity levels.
This is also the same with copper vs bronze. The specific price of the brass raw material depends on the alloy composition and purity, but more copper content generally means higher prices.
Machining Cost Drivers
Brass is cheaper to machine than copper, as there is lower tool degradation and better spindle management. Copper machining often involves more labor involvement, longer cycle times, and more money spent on tool monitoring and maintenance.
Lead Time and Production Throughput
Brass is significantly more machinable than copper, and this is reflected in the production speed and lead times. Copper CNC machining projects often require extended planning and turnaround times.
Prototype Manufacturing vs Volume Production Suitability
Brass can meet rapid prototyping service needs, as well as high-volume needs, because of its machinability and fast processing time. Due to longer cycle times and higher tool management requirements, copper machining is often more economical in specialized or lower-volume applications where conductivity outweighs production speed.
Brass vs Copper: Which Should You Choose?
There is no one-size-fits-all material when it comes to CNC machining. In even areas where copper obviously excels (electricals), there are still important considerations before making a manufacturing decision. Here are some of these considerations that can help guide engineers.
When Is Brass the Better Choice?
Brass is the better choice when:
- machinability and machining efficiency are the most important factors
- the final part needs to be tough and rigid
- aesthetics is a critical factor
- there is no opportunity for elaborate secondary surface finishing
When Is Copper the Better Choice?
Copper is the better choice when:
- the project involves electricals
- the final part requires high thermal conductivity
- the CNC parts are highly specialized
- complex wire geometries are needed
Brass vs Copper: Quick Selection Matrix
Here is a quick selection guideline to help your manufacturing decision.
| What do you need? | Which metal is better? |
| Fast CNC machining | Brass |
| Tight tolerance | Brass |
| Thin walls | Brass |
| High electrical conductivity | Copper |
| Heat transfer | Copper |
| High-volume production | Brass |
| Low tool wear | Brass |
| Better primary surface finish | Brass |
| Complex formed shapes | Copper |
| Low production cost | Brass |
Conclusion
The brass vs copper debate is not necessarily about which is universally better, but which is the best for your particular project needs. Brass has better machinability, lower production costs, and faster cycle times, but copper is simply the unavoidable option if conductivity is involved.
If you are an engineer looking for where to source custom copper and brass CNC machining services with brass or copper, you are at the right page. Reach out to FastPreci for a comprehensive assessment of your project needs and what would work best for you.
Frequently Asked Questions
Is Brass and Copper the Same?
No, brass and copper are not the same. Copper is a pure metal, while brass is an alloy of copper and zinc, typically containing 55 to 95% of copper and 5 to 45% of zinc. While they may have similar appearances, brass and copper are different metals and have different CNC properties.
Can Brass and Copper Be Used for Precision CNC Turning?
Yes, brass and copper can be used for precision CNC turning. However, brass is more suitable because of its better machinability, ability to allow higher cutting speeds, slower tool wear rate, and better surface finishing.
Is Brass Conductive Enough for Electrical Components?
Yes, brass is conductive enough for many electrical components, such as terminals, sockets, switches, and connectors. While brass does not measure up to copper in terms of electrical conductivity (25 to 40% IACS vs 98 to 100% IACS), brass may be preferred in instances where conductivity is needed in addition to high wear-resistance and strength.
