🟡 BRASS
Brass Machined Parts & Fittings — Burlington, VT Precision Suppliers
Ask a machinist which metal machines closest to cutting through butter and the answer is almost always free-machining brass — C360, the leaded alloy that Burlington's screw machine shops run at surface speeds exceeding 600 SFM with tool life measured in hours rather than minutes. Brass procurement in Burlington serves a pragmatic market: fluid system fittings for GE Aviation ground support equipment, semiconductor process gas fittings that need corrosion resistance without stainless complexity, and RF connector hardware where brass's electrical properties and dimensional stability make it the connector industry's standard substrate. C260 cartridge brass and naval brass round out the supply catalog for formed and corrosion-critical applications. Burlington suppliers who know brass know that alloy selection is the first decision, not an afterthought.
ISO 9001AS9100ISO 14001
C360 free-machining brass (61.5% Cu, 35.5% Zn, 3% Pb) is the undisputed king of machinability among common engineering metals. Its machinability rating is 100 — the reference standard against which all other metals are measured. The lead content creates a discontinuous chip-breaking phase that eliminates the long, stringy chips of leaded-free copper alloys, allows surface speeds of 500-800 SFM on CNC lathes, and produces sub-64 µin surface finish without special tooling. Burlington screw machine shops have run C360 for decades on fittings, valve bodies, standoffs, connectors, and threaded inserts because the combination of low cycle time, excellent tolerance capability (±0.0005" diameter on Swiss lathes), and moderate cost makes it the economic choice for precision turned parts that do not require the elevated corrosion resistance of stainless.
One critical application restriction applies to C360: the lead content makes it unsuitable for potable water applications under NSF/ANSI 61 lead leaching standards, and many European RoHS and REACH regulations restrict or prohibit leaded brass in end products. Burlington suppliers producing parts for drinking water systems, food-contact applications, or European export markets have shifted to C353 or C385 low-lead brass alternatives, or to C145 tellurium copper for the highest machinability among lead-free options. Defense and aerospace applications are generally not affected by lead restrictions, so C360 remains dominant in Burlington's military supply chain.
C260 cartridge brass (70% Cu, 30% Zn) delivers the best cold-forming response in the brass alloy family — its single-phase alpha microstructure deep-draws, bends, and stamps without the work-hardening rate or cracking risk that higher-zinc alloys present. Burlington fabricators producing drawn enclosures, stamped spring contacts, and bent tube assemblies specify C260 annealed when the forming operation demands a forgiving material. C260 is less machinable than C360 — machinability rating approximately 30 — because without lead, it produces continuous chips that can bird-nest. For parts that involve both complex forming and machined features, C260 handles the forming and screw-machined inserts in C360 are pressed or threaded in afterward.
Naval brass (C464, 60% Cu, 39% Zn, 1% Sn) adds tin to yellow brass for improved resistance to dezincification — the selective leaching of zinc from brass that occurs in corrosive water environments, particularly hot fresh water and seawater. The 1% tin addition substantially retards this mechanism. Burlington's energy infrastructure, marine supply, and water treatment equipment markets pull naval brass for pump bodies, valve seats, and fittings in service conditions where dezincification-inhibited alloy is required. Naval brass machines at approximately machinability 30 — similar to C260, and considerably harder to machine than C360.
High-Volume Brass Machining on CNC and Swiss Screw Machines
Burlington's precision machine shops run brass on several equipment platforms depending on part complexity and volume. For simple cylindrical turned parts — hex bolts, fittings, connectors, standoffs — traditional multi-spindle screw machines running C360 bar stock achieve cycle times of 5-15 seconds per piece on parts under 1" diameter. These machines are purpose-built for high-volume production of rotationally symmetric parts and represent the lowest per-piece cost for brass turned work at quantities of 1,000 to 100,000 pieces.
Swiss-type CNC lathes (Star, Citizen, Tsugami platforms) handle the precision end of brass turned work — thin-wall fittings, multi-diameter shafts with tight concentricity requirements, and parts with milled flats, cross-holes, or slots cut in the same setup as turning. On a Swiss lathe running C360, a 3/4" OD fitting with 10 operations can be completed in under 60 seconds from bar to finished part, holding ±0.0005" on critical diameters. Swiss machines excel at long, slender parts where the live guide bushing supports the stock close to the cutting tool, preventing deflection that would cause taper on unsupported cuts.
For prismatic brass parts — manifold bodies, custom RF filter housings, complex valve bodies with multiple intersecting bores — 4- and 5-axis machining centers replace the lathe as the primary platform. Brass's machinability advantage compounds here: milling cycle times in C360 are a fraction of equivalent operations in stainless or titanium, and tool life is essentially unlimited at practical cutting speeds. Burlington shops producing one-off or short-run brass components on machining centers quote quick turnaround because the per-piece cycle time is short and setup dominates the job cost.
Applications and Quality Requirements for Brass in Burlington's Aerospace and Semiconductor Sectors
Aerospace applications for brass in Burlington's supply chain concentrate in fluid systems, ground support equipment, and non-structural hardware rather than primary structure. Brass fittings in hydraulic and pneumatic test rigs for GE Aviation tooling — AN-style hex head fittings, Swagelok-compatible tube fittings, and test port adapters — use C360 because the fittings must thread precisely, seal reliably, and resist the hydraulic test fluids without plating or coating. AS9100 documentation requirements for these parts are typically less intensive than for flight-hardware parts, but drawing conformance, dimensional inspection, and material certification (copper alloy per ASTM B16 for round bar) are expected.
Semiconductor applications for brass focus on instrumentation fittings and support equipment rather than direct process contact. Compressed dry air fittings, vacuum rough-pump connections, and instrument manifold bodies in fab support areas commonly use C360 brass. Direct process gas contact in GlobalFoundries' fab typically requires stainless 316L or PTFE-lined fittings due to brass's copper content, which can be a contamination source in ultra-high-purity gas systems. Burlington procurement teams sourcing for semiconductor support infrastructure rather than process-direct applications can specify brass freely.
Electrical and RF applications are a steady demand category. Brass's electrical conductivity (27% IACS for C360) is considerably lower than copper or aluminum, but its mechanical stability, machinability, and cost make it the standard material for RF connector bodies (BNC, SMA, N-type), antenna hardware, and coaxial fitting bodies. The connector industry has standardized on brass with nickel or gold plating for decades because the machining economics are unmatched and the conductivity of the body is less critical than the conductivity of the plated contact surface.
Surface Finishing and Plating for Brass Components
Brass components in Burlington's defense and electronics supply chains almost universally receive surface finishing to prevent tarnish, improve appearance, and in many cases enhance electrical performance. The most common finish sequence for RF hardware is electroless or electrolytic nickel barrier plating followed by gold flash (0.00005–0.0001" gold over 0.0002" nickel) per MIL-DTL-45204. The nickel barrier prevents zinc migration from the brass substrate into the gold layer — a mechanism called dezincification of the plate that degrades solderability and conductivity over time. Burlington shops either plate in-house for high-volume connector work or use qualified platters in the Vermont-New Hampshire corridor.
For general industrial and aerospace fluid fittings, yellow chromate (zinc plating plus chromate per ASTM B633) provides adequate corrosion protection at low cost, producing the familiar yellow iridescent finish seen on commercial fittings. Clear chromate gives a lighter protective coating for applications where appearance matters but the yellow tint is undesirable. Electroless nickel without gold provides hard, corrosion-resistant surfaces for instrument panel hardware and mechanical connectors that see repeated assembly-disassembly cycles. Powder coat over brass is used for decorative architectural hardware and some industrial support structure applications where appearance is the primary driver.
For high-volume production plating on C360 screw machine parts, barrel plating — tumbling parts in a rotating barrel inside the plating bath — delivers economical coating of complex-shaped parts that would be impractical to rack individually. Barrel nickel or barrel tin finishes are common on standoffs, inserts, and connectors produced in thousands or tens of thousands per lot. Racked plating is reserved for parts with tight tolerance surfaces that cannot tolerate the ding and mark risk of barrel processing, or for parts with geometry features that trap solution and create non-uniform plating in barrel conditions.
Frequently Asked Questions
C360 free-machining brass achieves its unmatched machinability through the presence of 2.5-3.7% lead uniformly distributed in the microstructure as small lead globules. Lead is virtually insoluble in the brass matrix, so it sits at grain boundaries and within grains as discrete soft particles that act as chip breakers and lubricate the tool-chip interface. When a cutting tool shears through C360, the lead particles cause chips to break into small curls rather than forming long stringy ribbons, and they reduce friction between the chip and the tool's rake face. The practical result: cutting speeds of 500-800 SFM with carbide tooling versus 200-300 SFM for unleaded C260, tool life in hours rather than the minutes seen in copper, and consistent surface finish below Ra 32 µin in routine production without special tooling or process control. For a Burlington shop quoting 10,000 brass fittings, the difference between C360 and C260 in cycle time alone can represent 40-60% of total machining cost. C360 also drills cleanly to deep L/D ratios with standard carbide drills — critical for the cross-bore and deep-ported features common in valve bodies and fitting manifolds.
Naval brass (C464) is specified when the service environment creates risk of dezincification — the selective corrosion mechanism where zinc preferentially leaches from standard yellow brass, leaving a porous copper-rich sponge that has lost all structural integrity. Dezincification occurs most aggressively in hot fresh water (above 140°F), mildly acidic solutions, and marine environments with elevated chloride levels. The indicators that should trigger naval brass specification include: parts in contact with hot domestic water systems, heat exchanger tubes and headers in water-side service, marine pump and valve components, and water treatment equipment fittings. Vermont's water infrastructure and Lake Champlain-adjacent marine applications create real dezincification risk that standard C260 or C360 cannot reliably resist. Naval brass's 1% tin addition disrupts the electrochemical cell that drives zinc dissolution, providing substantially better resistance in these environments. For indoor air-side, vacuum, or hydraulic fluid applications where dezincification is not a risk, standard yellow brass grades provide adequate service life at lower material cost. Buyers should make a conscious decision rather than defaulting to naval brass for all applications, as its lower machinability (rating ~30 versus C360's 100) increases machining cost significantly.
C360's 2.5-3.7% lead content places it squarely in the scope of European Union RoHS (Restriction of Hazardous Substances) and REACH regulations, which restrict or prohibit lead in certain product categories and end uses. Current RoHS Directive 2011/65/EU restricts lead in electrical and electronic equipment (EEE) to a maximum of 0.1% by weight in homogeneous materials, with specific exemptions for certain applications. Many connector and electronics hardware applications that historically used C360 brass are subject to RoHS, and Burlington suppliers producing for European market customers must understand whether the end product falls under an exemption (several exist for copper alloys in certain categories) or requires a lead-free substitute alloy. REACH registration and SVHC (Substance of Very High Concern) reporting requirements apply to lead in articles above concentration thresholds. For domestic defense and aerospace customers, lead in brass is generally not restricted by current U.S. regulations. Burlington suppliers producing for international programs should work with their customers to determine applicable regulations before defaulting to C360, and qualify lead-free alternatives like C353 bismuth brass or C145 tellurium copper for restricted applications.
C360 free-machining brass reaches excellent surface finish in routine CNC turning without special polishing steps. On a CNC lathe with a sharp carbide insert, nose radius 0.015-0.031", and moderate feed rate (0.003-0.005" per revolution), turned OD finish consistently achieves Ra 32 µin or better. Reducing feed to 0.001-0.002" per revolution on a finish pass drops surface finish to Ra 16 µin or below — sufficient for most sealing, bearing, and contact surface requirements. Burnishing with a carbide or ceramic roller tool after turning can achieve Ra 4-8 µin on straight cylindrical surfaces by cold-working the peaks flat rather than cutting them away, and this approach also introduces compressive residual stress that improves fatigue performance. Drilled holes in C360 finish at Ra 64-125 µin; reaming with a well-sharpened reamer cuts this to Ra 32-63 µin; precision honing can reach Ra 8-16 µin for critical bore surfaces on valve seats and precision fits. Internal grinding of bore diameters in brass is rarely necessary given the alloy's machinability, but it is available at specialty shops in Vermont for applications requiring Ra below 8 µin with extremely tight cylindricity control.
Last updated: July 2026
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