A Comprehensive Guide to Brass CNC Machining

What is CNC Machining Brass?

CNC machining brass is a subtractive manufacturing process that typically employs CNC machine tools like carbide inserts and computerized controls. These machine tools work to remove layers of material from a brass workpiece.

The material removal rate is dependent on the spindle speed. This method facilitates manufacturing brass parts with higher precision and tight tolerances.

Brass is an alloy made from a combination of Copper and Zinc. Besides, it is one of the best materials for CNC machining when using the right tools. This metal alloy could also contain tin, lead, chromium, or magnesium, depending on its use.

The lead and copper content of brass boosts its machinability, making it quite easy to fabricate using the CNC brass machining.

Additionally, it has several good mechanical properties, including a low coefficient of friction, strong wear resistance, high corrosion resistance, ductility, and malleability.

What Properties of Brass Make It Suitable for CNC Machining?

Property	Brass
Melting point	885 to 890 ℃
Density	8.5 g/cm³
Modulus of Elasticity	97Gpa
Thermal Conductivity	115 W/m-k
Electrical Resistivity	6.3*10-8Ω

The properties of a brass alloy are dependent on its constituent metals, as well as their proportion.

The major components of brass are copper and zinc, but it could also contain magnesium, silicon, iron, or lead, metals that determine its grade.

Aside from grade determination, these metals’ proportion, presence, or absence also influence the brass alloy’s properties.

Here are other attributes of brass that make it suitable for CNC machining; 

Electrical and Thermal Conductivity

Brass is a good conductor of electricity and heat. This property is primarily due to the presence of copper in its composition.

The electrical and thermal conductivity of these brass alloys makes EDM a CNC brass machining process ideal for its machining.

Using this process helps save time due to faster machining speeds and the cost of brass part production while facilitating the production of electrical equipment with brass parts eg. heat sink.

Corrosion Resistance

Corrosion resistance is another property that makes brass a good choice for CNC machining. How much corrosion an alloy of brass can withstand depends on the level of iron and aluminum it contains.

The higher the quantity of aluminum, the higher its ability to resist corrosion. Conversely, the higher the iron content of the alloy, the lower its ability to resist corrosion.

The ability to resist corrosion ensures CNC machining brass tool life is longer. This alloy is also ideal for use in environments with high moisture content.

Malleability

Malleability denotes the ease with which machinists can manipulate metal into different shapes, and brass is highly malleable. The good malleability of this alloy makes it ideal for brass CNC machining resulting in the manufacture of brass custom parts.

The constituent of brass majorly responsible for its high degree of malleability is its copper content. Hence, brass alloys with a higher quantity of copper are more malleable than those with a lower quantity.

Strength and Hardness

Strength and hardness are properties of brass not often recognized, probably due to its low friction and ease of machining.

However, this metal alloy of copper, although not as strong as free machining steels, is quite strong and durable, requiring carbide-cutting tools for optimal fabrication. This strength is due to its aluminum alloy component, which often forms a hard layer of aluminum oxide on the surface of the alloy.

Highly Machinable

A high degree of machinability is one of the major properties of brass. Its machinability is due to its lead constituent. The lead component of this alloy makes it flexible and ductile, which makes fabricating it easier regardless of their level of experience.

Besides, the high machinability of this alloy is also one of the major reasons it has wide acceptability by machinists for CNC Machining.

Aesthetic Appeal

Brass, with its wide range of color variations, including reddish-gold, bright gold, or silvery white, gives ornamental applications to finished parts.

The exact color of brass depends on the proportion of its constituent elements. For instance, copper-zinc alloys with a higher percentage of copper often have a rosier tone, while those with a higher percentage of zinc have a silver tone.

This metal alloy’s natural finish makes it possible to use brass machined parts without additional surface finishing.

Commonly Used Brass Grades for CNC Machining

Different brass grades depend on the percentage of copper and zinc. These grades have their best uses, ornamental applications, advantages, and disadvantages.

These grades include C260, C272, C330, C353, C360, C385, C464 and C48200-C48500. However, the grades commonly used for CNC machining are the C360 and C260. Let’s examine these brass grades in more detail.

C360

This is the most common form of brass. Another name for C360 is free-cutting or free-machining brass due to its high lead content of approximately 3%.

Known for its high tensile strength and machinability, this free-machining brass is ideal for soldering and brazing operations. Its high degree of formability and resistance to stress corrosion cracking gives it application in producing fasteners, joints, screws, fittings, valves, and other hardware parts.

Advantages

• Excellent tensile strength
• Good corrosion resistance
• Excellent formability and machinability, free machining brass

Disadvantages

• High susceptibility to acid corrosion
• Lead content makes it less than ideal for use in the medical products manufacturing industry.

C260

This grade of brass, also known as cartridge brass or 70 30, has a warm yellow tone. Its favorable cold working properties, weldability, and formability, similar to commercial bronze, make it stand out.

This grade of brass is one of the most used materials for producing fasteners, ammo, hardware, and shells.

C260 is ideal for brass CNC machining due to its application in the electrical, consumer, plumbing, architectural world, and various industries.

Advantages

• Most ductile-grade of brass
• Excellent corrosion resistance
• A high degree of formability and workability

Disadvantages

• Not ideal for use with acetic, hydrochloric, and nitric acid
• Not ideal for use with most ammonia and ammonia compounds

Surface Finishes for CNC Machined Brass Parts

Machined brass often comes with a natural golden surface, which could serve as a natural finish.

However, depending on your brass part needs, you might want an external surface finish for your CNC brass machined parts. Below are some surface finishes available for CNC machined brass.

Polishing

This is a surface finishing process that improves the appearance of brass by first removing stock. It does this by taking out ruptured metal materials on the surface of the alloy. Honing also helps generate a cross-hatched pattern on the surface of the brass part, thus beautifying it.

Additionally, it helps guarantee the precision of the brass machined part, checking for straightness, roundness, and size.

As Machined

This means using the brass as machined without applying any external surface finish. When such brass is used, the focus is on its functionality instead of aesthetics.

However, surface finish often provides an added layer of protection, so using brass as machined could reduce its life span, as the risk of damage is considerably higher.

Powder Coating

This surface finish involves coating the surface of custom brass parts using the free-flowing dry powder.

Powder coating as a surface finish is highly beneficial as it helps improve the corrosion resistance of brass, durability, and longevity.

Electroplating

Brass with this surface finish appears smoother and glossier than their counterparts. The process involves using electrolysis to bind another metal’s molecules to the brass’s surface. Other metals used for this process include aluminum, stainless steel, etc. Brass is generally considered to be electroplated with chrome, zinc, silver, or gold.

Conclusion

Several properties make brass ideal for CNC machining, including corrosion resistance, high machinability, higher conductivity, and aesthetic appeal.

There are different grades of brass, but the most commonly used grades for CNC machining are C360 and C260.

Are you looking for a trusted company to machine brass parts? Contact AT-Machining, where professionalism, fast lead time, and quality are guaranteed.