Manufacturing engineers know the frustration: some metal components machine like butter, while others wear down tools and demand excessive time. The secret lies in the material's intrinsic properties. For precision parts requiring extensive machining, selecting the right alloy is critical. This article examines C36000 free-cutting brass—the material of choice for E-Z LOK fasteners—through an analytical lens, dissecting its physical, mechanical, and thermal characteristics to guide engineering decisions.
C36000 Free-Cutting Brass: Composition and Key Attributes
Renowned for its exceptional machinability, C36000 brass (UNS C36000) dominates precision component manufacturing. Its chemical blueprint reveals why:
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Copper (Cu):
60-63% (forms the brass matrix)
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Lead (Pb):
2.5-3.7% (critical for chip breaking)
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Zinc (Zn):
~35.5% (balances strength and cost)
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Iron (Fe):
≤0.35% (impurity control)
Machinability Secret:
Lead particles act as microscopic lubricants during cutting operations, reducing friction by 40-60% compared to lead-free alloys. This translates to faster feed rates, superior surface finishes (Ra ≤ 32 µin), and 300% longer tool life in production environments.
Physical Properties: Density and Real-World Implications
With a density of 8.49 g/cm³ (0.307 lb/in³), C36000 occupies a strategic middle ground between aluminum and steel. This property profile makes it ideal for:
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Weight-sensitive applications:
30% lighter than equivalent steel components
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Vibration damping:
15% better than aluminum in harmonic applications
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Corrosion resistance:
Excellent for marine hardware (ASTM B16 compliant)
Mechanical Performance: The Numbers That Matter
Extensive testing reveals why this alloy withstands demanding applications:
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Tensile Strength:
338-469 MPa (varies with temper)
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Yield Strength:
124-310 MPa (cold working increases this value)
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Elongation:
53% in 18" specimens (superior formability)
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Machinability Rating:
100% (industry benchmark)
Notably, its shear modulus of 37 GPa allows for clean thread cutting—a critical factor for fastener production.
Thermal Behavior: Managing Heat in Precision Components
When temperature becomes a design factor, C36000 demonstrates:
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Thermal Expansion:
20.5 µm/m·°C (requires compensation in tight-tolerance assemblies)
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Conductivity:
115 W/m·K (effective for heat dissipation)
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Melting Range:
885-900°C (advantageous for brazing operations)
Designer's Note:
The alloy's high CTE demands careful consideration when mating with stainless steel (CTE: 10-17 µm/m·°C) or titanium (CTE: 8.6 µm/m·°C) in thermal cycling environments.
Material Selection: When to Choose (and When to Avoid) C36000
This brass excels in:
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High-volume CNC turned parts
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Plumbing components requiring corrosion resistance
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Electrical contacts needing good conductivity
Alternative materials should be considered when:
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Lead content violates RoHS/REACH regulations
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Applications demand strengths >500 MPa
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Extreme temperatures exceed 200°C continuously
As with all material specifications, prototype testing under actual operating conditions remains essential. While C36000's datasheet values provide reliable baselines, real-world performance can vary with manufacturing processes, surface treatments, and environmental exposure.
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