Brass Machining & Precision Parts in Frederick, MD — C360, C260 & Naval Brass

C360 brass (61.5% Cu, 35.5% Zn, 3% Pb) is the most machinable of all common engineering alloys, with a machinability rating of 100% — the benchmark against which all other metals are measured. The lead addition (3%) acts as an internal chip breaker, producing short, brittle chips rather than the stringy, dangerous chips that plague copper and some aluminum alloys. At cutting speeds of 300–600 SFM on CNC screw machines and turning centers, C360 produces 32 µin Ra or better surfaces as a natural outcome of standard machining practice. Frederick shops running high-mix defense support programs use C360 for: threaded fittings for fluid systems, electrical connector housings and contacts, instrument hardware (knobs, adjustment screws, precision standoffs), and medical device sub-components for non-implant applications. The material is stocked in round bar from 0.125" to 3" diameter at local metal service centers with next-day delivery, which is a real advantage for shops supporting defense programs with tight delivery requirements. C360 is the obvious choice whenever machinability and cost efficiency are the primary drivers and the application doesn't require naval brass's dezincification resistance.

C260 brass (70% Cu, 30% Zn) is the forming grade — its higher copper content compared to C360 gives it significantly better cold-working ductility and deep-drawing performance. The name 'cartridge brass' reflects its historical use in ammunition manufacture, which remains relevant to Frederick's proximity to the defense supply chain. In modern applications, C260 appears as deep-drawn enclosures, formed electrical contacts, stamped terminal hardware, and sheet metal components that require bending or rolling without cracking. Machinability of C260 is lower than C360 (roughly 65% relative rating) due to the absence of lead and the higher copper content that makes it tougher and more prone to built-up edge. Frederick shops that fabricate C260 sheet and formed components typically specialize in press work and forming rather than high-speed turning. For buyers who need both formed C260 sheet components and machined C360 detail parts in the same assembly, confirming whether the shop handles both operations or will need to subcontract forming is an important qualification question.

Naval brass (C464, approximately 60% Cu, 39.25% Zn, 0.75% Sn) was originally developed for shipboard applications where seawater corrosion resistance was essential — the tin addition inhibits dezincification, the selective leaching of zinc from the brass alloy that causes structural weakening and porosity in aggressive water environments. In Frederick, naval brass appears primarily in defense facility plumbing, laboratory fluid system fittings, and components for field-deployable systems that may encounter saltwater or high-chloride environments. Naval brass machines reasonably well but not as freely as C360 — the tin addition that provides corrosion resistance also increases toughness and reduces the chip-breaking tendency. Cutting speeds of 200–350 SFM with positive-rake tooling and controlled feeds produce acceptable results. For fluid system fittings where dimensional control of NPT or metric threads is critical, shops verify thread gauges with calibrated Go/NoGo gauges as a standard quality step. Naval brass fittings used in government and defense facilities often require hydrostatic pressure testing after fabrication to verify leak-free assembly.

Bare brass maintains acceptable appearance and corrosion resistance in many applications, but defense and laboratory programs frequently specify additional finishing. Nickel plating over brass provides a barrier against tarnish and oxidation while improving wear resistance on contact surfaces — ASTM B689 (electroless nickel) is the common specification. Tin plating per ASTM B545 is widely used for electrical hardware to maintain solderability and prevent oxide formation on contact surfaces. Chrome plating over brass provides a hard, corrosion-resistant surface for decorative or wear-critical applications. An important RoHS and REACH compliance note: C360's lead content (3%) can be a regulatory issue for products sold in European markets or subject to certain US federal procurement regulations that restrict lead in plumbing components. The Reduction of Lead in Drinking Water Act (2011) bans lead-containing brass in potable water applications in the US — a real consideration for laboratory plumbing at Frederick research facilities. Lead-free brass alternatives (C27450, C69300) are available for these applications but machine significantly worse than C360; confirm with your application engineer whether lead content is a regulatory concern before defaulting to C360.