🟡 BRASS
Brass Swiss Machining: C360 Free-Cutting, C260 Cartridge and Naval Brass
If Swiss machining had a perfect material, it would be C360 free-cutting brass, the alloy against which every other metal's machinability is measured at a flat 100 percent. Brass turns fast, chips break into tidy crumbs that fall away from the guide bushing, finishes come off the tool bright and clean, and tool life stretches for hours, which is exactly why high-volume fittings, valve bodies, and connectors have been screw-machined in brass for a century.
ISO 9001ISO 14001AS9100
C360: the 100 percent machinability benchmark
C360 free-cutting brass contains roughly 2.5 to 3.5 percent lead, which acts as a chip-breaker and internal lubricant, giving it the defining machinability rating of 100 percent that the entire screw-machine industry uses as its yardstick. On a Swiss lathe this means high surface speeds, light cutting forces, small clean chips that evacuate themselves, and exceptional tool life, so cycle times are short and the machine runs unattended with confidence. Surface finishes of 16 to 32 microinch Ra come straight off the tool with minimal effort, and even fine threads and small cross-holes cut cleanly.
This is the material that makes high-volume brass screw-machine work cheap and reliable. Plumbing fittings, gas valve components, electrical connector pins, and instrument bodies are produced by the millions in C360 precisely because the alloy removes nearly every machining obstacle. When a part can be made in C360, it usually should be, because no other common metal matches its combination of speed, finish, and tool life on a Swiss machine.
The lead-free question and the C260/naval alternatives
C360's machinability comes from lead, and lead is increasingly restricted, particularly for plumbing and drinking-water parts under regulations like the U.S. Safe Drinking Water Act and similar global rules, and for RoHS-governed electronics. That has pushed many buyers toward low-lead and lead-free brasses (such as C27450, C69300/EnviroBrass, and bismuth-modified alloys), which machine well but not quite as effortlessly as C360, typically rating 60 to 90 percent and producing slightly stringier chips that need a touch more attention. For any potable-water or food-contact part, the lead-free route is now usually mandatory, so buyers should confirm the regulatory requirement at design time.
C260 cartridge brass (70/30) is a high-ductility alloy with little or no lead, prized for cold forming and deep drawing rather than machining; it can be turned but is gummier and far less free-cutting than C360, so it is chosen for its forming and corrosion properties, not for screw-machine efficiency. Naval brass (C464) adds tin for seawater corrosion resistance and is used for marine hardware; it machines acceptably but again not at C360's level. The practical guidance is to default to C360 for machinability, switch to a lead-free grade when regulation demands it, and reserve C260 or naval brass for the specific forming or corrosion properties that justify their poorer machinability.
Finishing, dezincification, and end-use fit
Brass parts often ship as-machined because the bright, clean turned surface is attractive and corrosion-resistant enough for many uses, but plating (nickel, chrome, tin) is common for appearance, wear, or solderability, and buildup must be accounted for on tight features. Brass deburrs easily because the chips break rather than roll, so secondary deburring is lighter than for soft copper or aluminum.
The corrosion failure mode to know is dezincification, where zinc leaches selectively out of certain brasses in aggressive or chloride-rich water, leaving a weak porous copper structure. For demanding water service, dezincification-resistant (DZR/CR) brasses or naval brass are specified to avoid it. This is the kind of detail a buyer should flag when a brass part will see prolonged water or marine exposure, because a standard C360 fitting that is perfect for a dry connector can fail in long-term aggressive water service. For most dry mechanical and electrical applications, standard brass is durable and maintenance-free, which is a large part of why it remains the default high-volume screw-machine material.
Frequently Asked Questions
C360 free-cutting brass is literally the benchmark: it carries a machinability rating of 100 percent that the entire screw-machine industry uses as its reference point. Its roughly 2.5 to 3.5 percent lead content acts as a chip-breaker and internal lubricant, so the metal cuts at high surface speeds with low cutting forces and breaks into small, clean chips that fall away from the guide bushing and evacuate themselves. The practical results are short cycle times, exceptional tool life often measured in hours, bright clean finishes of 16 to 32 microinch Ra straight off the tool, and confident unattended running. Fine threads, small cross-holes, and tight features all cut cleanly. This combination is why plumbing fittings, valve components, electrical pins, and instrument bodies have been produced in brass by the millions for over a century. When a part can be made in C360, it usually should be, because no other common metal matches its blend of speed, finish, and tool life on a Swiss lathe.
Because C360's machinability comes from lead, and lead is increasingly restricted for plumbing, drinking-water, and RoHS-governed parts, several low-lead and lead-free brasses have become standard alternatives. Common choices include low-lead alloys like C27450, lead-free grades such as C69300 (often sold as EnviroBrass), and bismuth-modified brasses that use bismuth in place of lead as a chip-breaker. These machine well, typically rating 60 to 90 percent machinability versus C360's 100 percent, producing slightly stringier chips that need a bit more attention to feeds and chip control, with modestly longer cycle times and somewhat higher tool wear. For any potable-water or food-contact part the lead-free route is now usually legally required under rules like the U.S. Safe Drinking Water Act and equivalents, so buyers should confirm the regulatory requirement at design time. For non-potable industrial and electrical parts, standard C360 often remains acceptable and most economical, so the right choice depends on the end-use compliance requirements.
Brass is one of the most cost-effective metals to Swiss machine on a per-part basis because its outstanding machinability gives short cycle times and long tool life, even though the bar stock itself is priced off the copper and zinc markets and is not cheap by weight. A small turned C360 fitting at production volume commonly runs $0.50 to $2.50 each, with the fast cycle and minimal scrap keeping the machining portion low. Lead-free brasses cost a modest premium in both material and machining time because they cut slightly slower and wear tooling a bit faster. Material price can swing with commodity copper and zinc, so quotes may be tied to the metals market. Lead times typically run 3 to 5 weeks for a first article and initial quantity, shorter on repeats, with optional plating adding 5 to 10 business days. Because brass parts often ship as-machined with their attractive bright finish, the absence of a mandatory protective coating can keep delivered costs lower than for carbon steel, which always needs corrosion protection.
Dezincification is a corrosion failure mode in which zinc leaches selectively out of a brass alloy, typically in aggressive, soft, acidic, or chloride-rich water, leaving behind a weak, porous, spongy copper structure that can fail mechanically and leak. It mainly affects higher-zinc brasses in prolonged water or marine exposure rather than dry mechanical or electrical service. You should flag it whenever a brass part will see long-term contact with potable water, well water, seawater, or process fluids, especially in fittings, valves, and plumbing components. The solution is to specify a dezincification-resistant brass (often labeled DZR or CR), which is alloyed and sometimes inhibited with a small arsenic addition to resist the attack, or to use naval brass (C464) with its tin addition for seawater service. For ordinary dry connectors, mechanical hardware, and indoor electrical parts, standard C360 or lead-free brass is durable and dezincification is not a concern. The key is to raise the question at design time when prolonged aggressive water contact is part of the application.
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Last updated: July 2026
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