In modern manufacturing, custom CNC brass parts have become core components in automotive, electronics, medical, aerospace, and other industries due to their excellent comprehensive performance. From micro connectors in precision instruments to transmission components in large machinery, CNC brass machining technology meets the stringent requirements of different industries for part precision, performance, and appearance through precise control and flexible customization. This article will comprehensively analyze the material selection, machining processes, quality control, and application scenarios of custom CNC brass parts, providing professional references for industry practitioners and demanders.
Unlocking the Manufacturing Secrets of Custom CNC Brass Parts

I. Brass Material Selection: The Fundamental Guarantee for Custom CNC Machining

1.1 Common Brass Grades and Machining Characteristics

The performance of custom CNC brass parts first depends on material selection. Different brass grades exhibit unique machining characteristics due to compositional differences:
  • C36000 Free-Cutting Brass: With a lead content of approximately 3%, it is a “star material” in CNC brass machining. Its cutting force is 18% lower than that of ordinary brass, chips are easily broken during machining, and surface roughness can be easily controlled below Ra1.6μm, making it suitable for mass production of precision bolts, nuts, connectors, and other parts. An electronics company used C36000 to machine USB interface terminals, increasing production efficiency by 22% and extending tool life by 30%.
  • H62 Ordinary Brass: Contains 62% copper and 38% zinc, offering both strength (tensile strength ≥300MPa) and ductility (elongation ≥30%). It can withstand complex forming processes in custom CNC machining and is commonly used in manufacturing valves, pipe fittings, and other parts requiring both pressure resistance and machinability. After cryogenic treatment (-196℃), the cutting vibration amplitude of H62 brass is reduced by 25%, making it particularly suitable for thin-walled part machining.
  • C69400 Silicon Brass: Contains 1.5%-3.5% silicon, featuring excellent corrosion resistance and wear resistance. Its machining performance is close to that of free-cutting brass, and it is lead-free and environmentally friendly. Widely used in custom CNC brass parts such as seawater desalination equipment and marine accessories, its seawater corrosion resistance is twice that of ordinary brass.

1.2 Matching Material Properties with Application Scenarios

When selecting brass grades, it is necessary to consider the service environment of custom CNC parts:
  • Electrical and Thermal Conductivity Requirements: For parts such as motor brushes and heat sinks, high-purity brass (e.g., H90) is preferred, with a conductivity of up to 90% IACS;
  • Wear Resistance Requirements: For transmission parts such as gears and bearings, tin-containing brass (e.g., HSn70-1) is suitable, with a surface hardness of over HV100;
  • Environmental Requirements: Lead-free brass (e.g., C69400) must be used in drinking water equipment, medical devices, and other fields to meet RoHS, FDA, and other environmental standards.

II. Core CNC Machining Processes: Pursuing Both Precision and Efficiency

2.1 Turning: Precision Control in Rotation

CNC turning is the core process for machining shaft and disc-type custom brass parts. Taking the machining of a 50mm diameter C36000 brass bar as an example:
  • Rough Machining Parameters: Spindle speed 1500rpm, feed rate 0.15mm/r, cutting depth 1mm for rapid stock removal;
  • Finish Machining Parameters: Speed 3000rpm, feed rate 0.05mm/r, cutting depth 0.2mm. Combined with cemented carbide tools (rake angle 12°, clearance angle 8°), dimensional accuracy of ±0.005mm and surface roughness of Ra0.8μm can be achieved;
  • Special Process: Using a CNC sliding headstock lathe to machine slender parts with a length-to-diameter ratio >5 (such as instrument pointer shafts). Through guide bushing support, workpiece deformation is reduced, and straightness can be controlled within 0.01mm/100mm.

2.2 Milling: Precise Forming of Complex Contours

CNC milling can achieve custom machining of complex features such as planes, cavities, and curved surfaces. In brass gear machining:
  • Using a 5-axis machining center with a trochoidal milling strategy, a cutting speed of 200m/min, and a feed per tooth of 0.08mm can ensure gear tooth accuracy reaches grade 7 (GB/T 10095) with tooth surface roughness Ra≤0.8μm;
  • For deep cavity parts (depth >50mm), a high-pressure internal cooling system (pressure 3MPa) delivers cutting fluid directly to the tool edge, increasing chip evacuation efficiency by 3 times and avoiding secondary scratches. A precision mold factory shortened the machining time of custom brass cavity parts by 45% by optimizing milling paths.

2.3 Drilling and Tapping: Technical Points for Small Hole Machining

Hole machining of custom CNC brass parts needs to address chip evacuation and precision issues:
  • Drilling Process: For Φ3mm small holes, high-speed steel drills (118° point angle) are used with a speed of 3000rpm, feed rate of 0.1mm/r, and emulsion cooling. Hole diameter tolerance is controlled within ±0.01mm, and hole wall roughness is Ra3.2μm;
  • Thread Machining: For M10 and smaller threads, CNC thread milling is recommended instead of traditional tapping. Through helical interpolation movement, the feed rate is synchronized with the thread pitch (e.g., 1.5mm feed rate for 1.5mm pitch), avoiding tap breakage risks and increasing efficiency by 3 times.

III. Custom Machining Full Process: Quality Control from Design to Delivery

3.1 Design and Programming: Digital Process Preparation

The quality of custom CNC brass parts starts from the design stage:
  • CAD Modeling: Using software such as SolidWorks and UG to create 3D models, specifying tolerance grades (e.g., IT5-IT7), surface roughness, and other technical requirements;
  • CAM Programming: Generating toolpaths through Mastercam, PowerMILL, and other software, and using the “remaining material recognition” function to reduce air cutting strokes. For example, when machining complex cavities, trochoidal milling paths can reduce tool load by 30% and reduce built-up edge formation;
  • Simulation Verification: Using VERICUT software for cutting simulation to detect collision and overcutting risks. An enterprise reduced trial cutting scrap rate from 5% to 0.5% through simulation verification.

3.2 Clamping and Tooling: Foundation for Stable Machining

  • Clamping Solutions: Small parts use hydraulic chucks (clamping force fluctuation <0.5MPa), thin-walled parts use vacuum suction cups or soft jaws to avoid deformation; large parts use three-point positioning to ensure positioning error <0.003mm;
  • Tool Selection: Tungsten carbide coated tools (TiAlN coating) for rough machining, diamond-coated tools (coating thickness 3-5μm) for finish machining with a cutting edge radius of R0.02mm, enabling mirror finishing (Ra≤0.2μm).

3.3 Heat Treatment and Surface Treatment: Performance and Appearance Enhancement

  • Heat Treatment Process: Stress-relief annealing (500-600℃ for 2 hours) for stressed parts to eliminate machining stress, controlling hardness fluctuation within HV5;
  • Surface Treatment:
    • Polishing: Mechanical polishing (400#-2000# sandpaper) + chemical polishing (30% nitric acid + 20% sulfuric acid solution) achieves surface roughness up to Ra0.08μm;
    • Electroplating: Nickel plating with a thickness of 5-15μm improves corrosion resistance, passing 48-hour salt spray test without rust;
    • Passivation: Treatment with phytic acid passivation solution (8ml/L phytic acid + 30ml/L hydrogen peroxide) increases corrosion resistance by 3 times with no chromium pollution.

3.4 Quality Inspection: Comprehensive Precision Control

Custom CNC brass parts undergo multi-dimensional inspection:
  • Dimensional Inspection: Coordinate measuring machine (accuracy ±0.001mm) inspects critical dimensions with a measurement point density ≥0.5mm/point;
  • Surface Inspection: Roughness tester (resolution 0.001μm) measures Ra value, and white light interferometer analyzes microtopography;
  • Performance Inspection: Metallographic microscope observes grain structure, and hardness tester (100g load) detects surface hardness to ensure compliance with drawing requirements.

IV. Industry Application Cases: Diverse Scenarios of Custom CNC Brass Parts

4.1 Electronics and Electrical Field

Custom CNC brass parts are indispensable in precision components such as connectors and terminals. A communication equipment manufacturer’s 5G base station connectors use C36000 brass, formed in one piece through CNC turn-mill compound machining. Pin concentricity is controlled within 0.01mm, and contact resistance ≤10mΩ, meeting high-frequency signal transmission requirements.

4.2 Automotive Industry

In automotive fuel systems, custom brass valve parts must withstand 10MPa pressure and -40℃-120℃ temperature fluctuations. Using H62 brass after CNC precision machining and nitriding treatment, the valve sealing surface flatness is ≤0.005mm, with a service life of 100,000 cycles without leakage.

4.3 Medical Devices

Custom CNC brass gears in infusion pumps use lead-free brass C69400. Through laser micro-texturing (surface micro-pit diameter 50μm), the friction coefficient is reduced from 0.3 to 0.15, and operating noise is reduced by 15dB, meeting medical equipment mute requirements.

V. Frequently Asked Questions

5.1 How to Reduce the Machining Cost of Custom CNC Brass Parts?

Cost can be controlled by optimizing design (e.g., simplifying complex structures), selecting free-cutting materials (e.g., C36000), increasing order quantity (batch of 1000 pieces or more can reduce unit price by 15%-20%), etc. Meanwhile, using turn-mill compound machining to reduce clamping times can lower labor costs by 30%.

5.2 What to Do if Custom Brass Parts Have Surface Oxidation and Discoloration?

During machining, use cutting fluids containing corrosion inhibitors (e.g., benzotriazole), and perform passivation treatment within 24 hours after machining; store in a dry environment (humidity ≤60%) and avoid contact with sweat, acids, and alkalis. Oxidized parts can have the oxide layer removed through chemical polishing (nitric acid + hydrochloric acid solution) and then re-passivated.

5.3 How to Ensure Dimensional Stability of Custom CNC Brass Parts?

Select aged brass materials (aging time ≥72 hours); control ambient temperature during machining (20±1℃); perform stress-relief annealing on precision parts (300℃ for 1 hour); use online inspection and compensation systems to real-time correct thermal deformation errors.
If you need to customize high-precision CNC brass parts or have questions about material selection and machining processes, welcome to leave an online message for consultation. With 15 years of custom CNC brass machining experience, we can provide full-process services from design optimization to mass production to safeguard your products!

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