Brass is a metal alloy composed primarily of copper and zinc, with lead often added to enhance machinability. It's a popular choice for CNC machined parts due to several advantageous properties:

• Excellent machinability: Brass is among the easiest metals to machine, allowing for complex geometries, fine details, and excellent surface finishes
• Electrical and thermal conductivity: While not as conductive as pure copper, brass offers very good electrical and thermal properties
• Corrosion resistance: Naturally resistant to many forms of corrosion and develops a protective patina
• Low friction properties: Makes it ideal for components with moving parts like gears, bearings, and valves
• Attractive appearance: Distinctive golden color that can be polished to a high shine for decorative applications
• Cost-effectiveness: More affordable than many other engineering metals while still offering excellent properties

These properties make brass an excellent choice for applications in plumbing, electrical, automotive, marine, and decorative industries where a combination of performance, appearance, and value is required.

The main differences between brass grades relate to their composition, primarily the ratio of copper to zinc and the presence of other elements like lead. Here's a comparison of our most commonly used brass grades:

• Brass C360 (Free-Cutting Brass): Contains approximately 61.5-64.5% copper and 2.5-3.5% lead. Excellent machinability, good strength, and corrosion resistance. Best for: precision components, parts requiring complex machining.
• Brass Cz121 (Free-Cutting Brass): Contains approximately 57-59% copper and 2.5-3.5% lead. Similar to C360 but with slightly higher zinc content. Best for: general-purpose components requiring good machinability.
• Brass C260 (Cartridge Brass): Contains approximately 70% copper with no lead. More ductile and better for forming operations. Best for: parts requiring forming, bending, or stamping after machining.
• Naval Brass C464: Contains copper, zinc, and tin (1%). Superior corrosion resistance, especially in marine environments. Best for: marine applications or outdoor use.

When selecting a brass grade, consider these factors:

• How complex is the part geometry? (More complex parts benefit from free-cutting grades like C360)
• Will the part be exposed to corrosive environments? (Marine applications may require Naval brass)
• Are electrical properties important? (Higher copper content improves conductivity)
• Will the part contain threads or require good surface finish? (Lead content improves these aspects)

Our engineering team can provide guidance on selecting the optimal brass grade for your specific application requirements.

Brass is one of the most dimensionally stable and machinable metals, allowing for excellent tolerances. At BZ Metal Products, we can achieve the following tolerances for brass CNC machined parts:

• Standard tolerances: ±0.125mm (±0.005″)
• Precision tolerances: ±0.05mm (±0.002″)
• High-precision tolerances: Down to ±0.025mm (±0.001″) for critical features

Factors that may affect achievable tolerances include:

• Part geometry and complexity
• Overall part size (larger parts typically have wider tolerances)
• Feature type (holes, slots, etc.)
• Wall thickness (very thin walls may be more prone to distortion)

It's important to note that tighter tolerances generally increase machining time and cost. We recommend specifying precise tolerances only for critical features while allowing standard tolerances for non-critical dimensions to optimize cost-efficiency.

We offer several surface finishing options for CNC machined brass parts:

• As-machined: The natural finish directly from CNC machining. Brass typically machines to a smooth finish with fine tool marks visible.
• Polished: Mechanical polishing to create a bright, reflective surface. Multiple grades available from semi-bright to mirror finish.
• Brushed: A directional satin finish that reduces glare while maintaining the brass appearance. Popular for architectural and decorative applications.
• Bead blasted: A uniform matte finish created by impacting the surface with fine glass beads. Provides a consistent appearance that hides minor imperfections.
• Clear coating: A protective clear lacquer that preserves the brass appearance and prevents tarnishing.
• Nickel plating: A bright silver-colored plating that provides additional hardness and corrosion resistance.
• Chrome plating: A highly reflective, hard surface finish that offers excellent wear and corrosion resistance.
• Gold plating: A thin layer of gold that enhances the appearance while improving conductivity and corrosion resistance.

The choice of surface finish depends on the functional requirements of your part (corrosion resistance, wear properties, electrical conductivity) as well as aesthetic considerations. Our team can recommend the optimal finish based on your application.

When designing parts for brass CNC machining, consider these design best practices:

• Wall Thickness: Maintain a minimum wall thickness of 0.75mm (0.03") to prevent warping or deformation during machining.
• Internal Corners: Design with a radius rather than sharp internal corners. We recommend a minimum radius of 1/3 the depth for internal corners.
• Deep Pockets: For deep pockets, maintain a reasonable depth-to-width ratio (typically less than 4:1) to allow proper tool access.
• Holes: For small holes, keep the depth-to-diameter ratio under 4:1. Standard drills can typically achieve a depth of 10x diameter, but precision decreases with depth.
• Threads: Internal threads should have a minimum of 3 full threads engaged for strength. External threads should have a minimum diameter of 0.8mm.
• Tolerances: Specify tight tolerances only on critical features and allow standard tolerances elsewhere to optimize cost.
• Surface Finish: Consider if any surfaces require specific finish callouts or if standard machined finish is acceptable.
• Text & Markings: For engraved text, maintain minimum letter height of 1mm and line width of 0.2mm for legibility.

Brass is highly machinable, which allows for more complex designs than many other metals. However, following these guidelines will help ensure your parts are manufacturable at the best possible quality and cost.