A Guide to Brass CNC Machining

Key Takeaways

1. Brass is a copper-zinc alloy with high electrical and thermal conductivity.

2. Zinc improves strength and workability, while lead additions enhance machinability.

3. Free-cutting brass (C3602, C3604) is commonly used for precision CNC machining.

Overview

Brass is an alloy of copper and zinc known for its beautiful golden hues and excellent machinability. While retaining copper’s core characteristics, brass offers improved workability and strength. The zinc content affects both color and hardness: higher zinc lightens the color and increases hardness but also brittleness. Most brass used for cutting has a zinc content of 40% or less.

Key Properties of Brass

High Electrical Conductivity

As a copper alloy, brass retains high electrical conductivity. Pure copper's electrical resistance is the second lowest after silver, so it is used in power transmission equipment and electronic device components. While lower than pure copper due to its zinc content, brass is strong and workable, making it ideal for connectors, power outlets, and electronic device components.

High Thermal Conductivity

Brass also has excellent thermal conductivity, slightly lower than pure copper, but sufficient for heat transfer applications.

Excellent Workability

Brass excels in hot forging and can be heated and formed into complex shapes.

Brass is highly ductile and malleable, allowing it to be drawn into thin wires or formed into sheets. Malleability is the property of being formed into a thin sheet when subjected to compressive force, and ductility is the property of being drawn into a thin wire when subjected to tensile force.

Adding lead enhances the machinability of brass. It is a suitable material for parts requiring high-precision machining such as watch components, bolts, and nuts.

Superior Antibacterial Performance

Brass inherits copper’s natural antibacterial properties, which inhibit bacterial growth.

Types of Brass

Brass Type 1 (C2600)

• 70% copper, 30% zinc

• Excellent ductility, deep drawability, and plating characteristics.

• Also known as "7-3 brass"

Brass Type 2 (C2680)

• 65% copper, 35% zinc

• Excellent ductility, deep drawability, and plating characteristics.

• Also known as "6-4 brass"

Brass Type 3 (C2801)

• 60% copper, 40% zinc

• High-strength brass for component applications.

Free-Cutting Brass (C3602, C3604)

• Brass Type 3 has lead added to improve machinability

• Ideal for cutting and high-quality finished surfaces.

• Can undergo welding and plating.

Naval Brass (C4641)

• Brass with added tin for improved corrosion resistance and hardness

• Suitable for forging and welding, not ideal for cutting.

Precautions When Using Brass

While brass is a metal with excellent corrosion resistance, it corrodes slowly in air, forming a protective copper oxide layer (blackening) that prevents interior damage. Surfaces may oxidize, discolor, or develop bluish-green rust from fingerprints or sweat if it hasn't been treated with processes such as plating or clear coating.

Furthermore, brass is chemically reactive with rubber products, which can cause corrosion when in contact.

Applications of Brass

Brass is utilized in many applications, including:

• Precision machinery, including banknote printing presses

• Water supply pipes and toilet components

• Scientific and chemical instruments

• Model railways, ammunition casings, and metal models

• Buddhist altar fittings and brass musical instruments

• Japanese 5-yen coins (since 1948), as a gold substitute (“poor man’s gold”)

• Electrical connectors and outlets, leveraging high conductivity

Brass CNC Machining at Yumoto Electric

Yumoto Electric delivers high-quality components fast, worldwide. We provide precision machining for a wide range of metals using milling, turning, and specialized metal processing. We have experience with over 200 materials including aluminum alloys, stainless steel, molybdenum, and titanium. 

If you’re unsure about material selection or machining methods, we offer complimentary consultations to help optimize your design and production. For any questions, please feel free to contact us.