A Buyer's Guide to Common Bronze Alloys for Precision Machined Parts

Selecting the perfect material for your precision machined parts is crucial for performance and longevity. But when it comes to bronze, the variety of alloys available can sometimes feel overwhelming. Each bronze alloy offers a unique blend of properties – like strength, wear resistance, corrosion resistance, and machinability – making them suitable for demanding applications across various industries.  

To help you navigate these options, this guide compares the common bronze alloys we frequently machine here at Spex:

• Phosphor Bronze (C510)
• Silicon Bronze (C655)
• Manganese Bronze (C862)
• Tin Bronze (C905)
• Bearing Bronze (C932)
• Aluminum Bronze (C954)

Our goal is to provide clear insights into their characteristics and typical uses, helping you to make more informed decisions for your projects.

With over 75 years of experience in precision machining, Spex has deep expertise working with these versatile materials. We're here to help you find the right fit.

Why use bronze for precision parts?

So, what makes bronze alloys such a popular choice for precision components?

They offer a compelling mix of properties: excellent resistance to wear and corrosion, good strength, and in some cases, useful electrical or thermal conductivity. Many bronze alloys also stand up well to demanding environments, including marine applications.

These characteristics are highly valued in the industries we serve. Think durable bushings and gears for precision hardware, reliable connectors for power & electrical equipment, corrosion-resistant fittings for HVAC & Heat Exchange systems, and long-lasting components for Measurement & Instrumentation devices. Choosing the right bronze ensures parts perform reliably under specific operating conditions.

C93200 (SAE 660) – The Workhorse Bearing Bronze

Often called Bearing Bronze or SAE 660, C93200 is a true workhorse in the bronze family, valued for its balance of properties and manufacturability.

Key Characteristics:

• Excellent Machinability: With a machinability rating of 70 (where free-cutting brass is 100), it's one of the easiest bronze alloys to machine efficiently.
• Good Wear Resistance & Anti-Friction Properties: It offers reliable performance in applications involving friction and wear, conforming well to irregularities.
• Good Hardness & Strength: Provides durability for many general-purpose, medium-load applications.
• Reliable Corrosion Resistance: Holds up well against seawater and brine.

Typical applications of bearing bronze

‍Thanks to its properties and excellent machinability, C932 is widely used across many industries for parts like:

• Bushings & Bearings: Its most common use, ideal for general utility bearings under medium loads and speeds.
• Washers & Thrust Washers.
• General Machine Parts.
• Pump Components & Impellers.
• Automotive Fittings.

Machining Notes

‍Its lead content contributes significantly to its excellent machinability. This generally allows for higher machining speeds, smoother surface finishes, and better tool life compared to less machinable bronze alloys, making it cost-effective for production runs.

C95400 – The High-Strength Aluminum Bronze

C95400 is a popular aluminum bronze, known for its impressive strength and toughness, especially when compared to standard tin bronzes. It's often selected for more demanding applications where other bronzes might fall short.

Key Characteristics:

• High Strength & Hardness: It offers excellent mechanical properties, making it suitable for heavy-duty, high-load applications.
• Excellent Corrosion Resistance: Particularly effective against seawater, chlorides, and many chemicals, making it ideal for marine and industrial environments.
• Good Wear & Abrasion Resistance: Stands up well under high loads and in conditions where abrasion is a concern.
• Heat Treatable: Unlike many bronzes, C954 can be heat treated to further enhance its mechanical properties for specific requirements.
• Good Performance at Elevated Temperatures: Retains its strength better at higher temperatures than many other bronze alloys.

Typical applications of aluminum bronze

‍Its robustness makes C954 a go-to choice for demanding components, such as:

• Bushings & Bearings: Especially for high-load, lower-speed applications where strength and wear resistance are critical.
• Valve Components: Including valve bodies, seats, and guides that require durability and corrosion resistance.
• Pump Parts: Suitable for components handling pressure and potentially corrosive fluids.
• Machine Parts: Used in various heavy-duty industrial equipment components like pressure blocks or landing gear parts.
• Gears & Worm Gears: While Spex focuses on other precision components, C954 is commonly specified for gears in various machinery due to its strength and wear properties.
• Pickling Equipment Hooks/Baskets & High-Strength Clamps.

Machining Notes

‍C95400 has good machinability for a high-strength bronze, with a rating of 60 (where free-cutting brass is 100). While more machinable than many stainless steels, its toughness requires rigid machine setups, sharp tooling (carbide is often recommended), and appropriate speeds and feeds to achieve precise results and good surface finishes.

C51000 (Phosphor Bronze 510) – The Spring & Connector Specialist

C51000, commonly known as Phosphor Bronze or Phos Bronze Grade A, stands out for its excellent spring qualities, good strength, and formability. The addition of phosphorus increases wear resistance and stiffness.

Key Characteristics:

• Excellent Strength & Ductility: Offers a desirable combination of strength and the ability to be formed without breaking.
• Superior Fatigue & Spring Properties: Known for its resilience and ability to withstand repeated flexing or stress cycles, making it ideal for spring-loaded components.
• Good Corrosion Resistance: Provides reliable performance, holding up well in various environments, including marine atmospheres.
• Good Electrical Conductivity: Suitable for carrying electrical current, making it a choice for connectors and contacts.
• Excellent Cold Workability: Can be easily shaped and formed through processes like bending, stamping, and drawing without needing heat.

Typical applications of phosphor bronze

‍Its unique blend of properties makes C510 popular for intricate and functional parts like:

• Electrical Components: Connectors, terminals, fuse clips, switch parts, contact blades.
• Springs & Electromechanical Springs.
• Bellows, Diaphragms & Bourdon Tubes.
• Fasteners & Washers.
• Bushings: Particularly sleeve bushings where good wear resistance and formability are needed.
• Precision Instrument Parts.

Machining Notes

‍Phosphor Bronze C51000 has lower machinability compared to leaded or aluminum bronzes, with a rating of 20 (where free-cutting brass is 100). Machining requires careful attention to tooling (sharp tools are essential), appropriate speeds and feeds, and potentially robust workholding. Managing chip formation is key, as it can produce long, stringy chips.

C65500 – The Corrosion-Resistant Silicon Bronze

C65500, often referred to as High Silicon Bronze A, is valued primarily for its excellent corrosion resistance combined with respectable strength, making it a staple for hardware and components exposed to demanding environments.

Key Characteristics:

• Excellent Corrosion Resistance: Stands up very well against freshwater, saltwater, fog/mist, and many chemicals, making it highly suitable for marine applications and outdoor exposure.
• Moderate Strength: Offers good mechanical properties, suitable for various structural and hardware applications where high strength isn't the primary driver.
• Good Formability: Has good capacity for being shaped through both hot and cold working processes.
• Excellent Weldability: Considered one of the better bronze alloys for welding using various methods, especially Gas Shielded Arc Welding (GMAW/MIG). Brazing and soldering are also rated highly.

Typical applications of silicon bronze

‍Its blend of corrosion resistance, moderate strength, and good formability makes it a frequent choice for:

• Marine Hardware & Fittings: Components used on boats or near the ocean.
• Fasteners: Bolts, nuts, screws, and U-bolts, particularly where corrosion resistance is needed.
• Valve Stems & Guides: Parts requiring strength and resistance to various fluids.
• Pole Line Hardware: Electrical transmission and distribution line components exposed to weather.
• Hydraulic Pressure Lines & Piping Systems Components.
• Chemical Processing Equipment Components.

Machining Notes

‍Silicon Bronze C65500 has fair machinability, with a rating of 30 (where free-cutting brass is 100). Similar to C510 phosphor bronze, machining it successfully requires sharp tooling, appropriate speeds and feeds, and good lubrication. Careful chip management is beneficial.

C90500 (Tin Bronze / SAE 62) – The Strong & Pressure-Tight Choice

C90500, also known as Gunmetal or SAE 62 Tin Bronze, is a classic copper-tin alloy well-regarded for its good strength, toughness, and excellent corrosion resistance, particularly in seawater.

Key Characteristics:

• Good Strength & Wear Resistance: Suitable for applications involving moderate to heavy loads and requiring durability, especially at lower speeds.
• Excellent Corrosion Resistance: Highly resistant to seawater and brine, making it a traditional choice for marine hardware and pump/valve components.
• Good Pressure Tightness: Its casting characteristics make it suitable for components that need to contain pressure reliably, such as valve bodies and steam fittings.
• Good Solderability & Brazability: Can be effectively joined using soldering and brazing techniques.

Typical Applications of tin bronze

‍This alloy's robust combination of strength and corrosion resistance makes it suitable for parts like:

• Pump & Valve Components: Including bodies, impellers, piston rings, and steam fittings, especially those handling water or brine.
• Bushings & Bearings: Particularly suited for applications with heavy loads operating at lower speeds.
• Structural Components: Such as expansion bearings and fittings used in heavy construction or movable bridges.
• Marine Fittings & Hardware.
• Gears: While Spex focuses on machining other precision components, C905 is frequently specified for worm gears and gear blanks in various equipment due to its load-carrying capacity and wear characteristics.

‍Machining Notes

‍C90500 Tin Bronze has fair machinability, with a rating of 30 (where free-cutting brass is 100). Similar to other non-leaded tin bronzes like C510, machining requires attention to sharp tooling, appropriate speeds and feeds, and good lubrication to achieve the desired tolerances and surface finish while managing chip formation effectively.

C86200 – The Tough Manganese Bronze

C86200 is a high-strength manganese bronze, recognized primarily for its exceptional toughness, strength, and durability. It's typically reserved for heavy-duty applications where components face severe loads and stresses.

Key Characteristics:

• Very High Strength & Toughness: This alloy offers excellent tensile strength and the ability to withstand significant impact and heavy loads without fracturing.
• Good Wear Resistance: Performs well in applications involving friction and wear, especially under high-pressure conditions.
• Good Corrosion Resistance: Provides reliable resistance to corrosion, suitable for demanding industrial and some marine environments.
• High Load Capacity: Specifically engineered to handle significant stress and pressure effectively.

Typical applications of manganese bronze

‍Its extreme toughness makes C86200 suitable for components subjected to severe operating conditions, such as:

• Heavy-Duty Bushings & Bearings: Used in equipment like earth-moving machinery, cranes, steel mill equipment, or anywhere high loads are common.
• Structural Components: Including frames, struts, clamps, and hooks requiring high strength.
• Machine Parts: High-strength components in industrial machinery, press dies.
• Marine Castings & Rudders.
• Gears: C86200 is often specified for high-strength gears and worm gears found in heavy machinery due to its robustness.

Machining Notes

‍Manganese Bronze C86200 has fair machinability, generally rated around 30 (where free-cutting brass is 100), though some sources rate it slightly lower. Its significant strength and toughness make it more challenging to machine than alloys like C932 or even C954. Success requires very rigid machine setups, powerful equipment, sharp and durable tooling (carbide is strongly recommended), optimized (often slower) speeds and feeds, and effective cooling to manage heat generation and prevent rapid tool wear.

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Partnering with Spex for your bronze machining needs

As you can see, choosing the optimal bronze alloy involves balancing specific performance needs, budget considerations, and the practicalities of manufacturing. It's not always a straightforward decision, and selecting an alloy that's difficult to machine can impact lead times and costs.

That's where Spex comes in. We strive to be more than just a manufacturer; we aim to be your reliable partner  in sourcing precision machined components. Our team understands the nuances of these different bronze alloys and their suitability for various applications across industries like Power & Electrical, Measurement & Instrumentation, and Precision Hardware. We can help you consider the trade-offs and select a material that truly fits your requirements.  

Whether you need complex parts via CNC milling or turning, or high-volume runs on our Swiss machines, we have the capability and expertise to machine various bronze alloys to your exact specifications. With over 75 years in business and our commitment to quality backed by ISO 9001:2015 certification, you can count on Spex for consistent, high-quality bronze parts delivered on time.  

Selecting the right bronze alloy is a critical first step towards ensuring the performance and longevity of your components. With diverse properties and machining characteristics impacting everything from durability to cost, making an informed choice matters significantly. Spex combines deep material knowledge with advanced machining capabilities to deliver the precision bronze parts your application demands, consistently and reliably.

Ready to discuss which bronze alloy is best suited for your specific project, or need a quote for precision bronze components?

Contact Spex today! Let our team put our bronze machining expertise to work for you.