C83600 is the classic "85-5-5-5" leaded red brass, also widely known as gunmetal: roughly 85% copper with tin, zinc, and lead each making up about 5% of the balance. It's a sand-cast bearing and pressure-tight alloy, poured to near-net shape rather than supplied as bar stock, and it's arguably the single most common copper-alloy casting specification in the plumbing and valve industry. Its European equivalent, Rg5 (DIN CuSn5ZnPb), is specified just as widely across water-works and marine hardware in Europe.

The balance of elements gives C83600 a useful mix of properties: the tin provides strength and a natural resistance to dezincification and dealloying corrosion, the zinc improves fluidity in the mold and helps deoxidize the melt for sound, pressure-tight castings, and the lead is there for machinability and a self-lubricating bearing surface. That combination is why C83600 shows up everywhere from potable-water valve bodies and pump housings to small bushings, gears, and general-purpose hardware where a good balance of strength, corrosion resistance, and machinability matters more than maximum bearing load capacity.

C83600's roughly 5% lead content is what makes this alloy a shop favorite despite being a sand casting rather than wrought bar stock. The lead exists as fine, insoluble particles distributed through the copper-tin-zinc matrix. As the tool advances, those particles shear ahead of the cutting edge and break the chip into short, manageable segments instead of letting it curl into a continuous ribbon, while simultaneously depositing a thin lubricating film that reduces friction at the tool-chip interface.

The practical payoff is lower cutting forces, cooler tool temperatures, and a strong resistance to built-up edge formation — the gummy smearing that plagues lead-free bronzes and pure copper. Surface finish is typically very good even on general-purpose tooling, and tool life is long because the material presents little abrasive resistance to the cutting edge. The caveats are the ones inherent to any sand casting: internal porosity in thicker sections, a harder oxidized skin on as-cast surfaces that benefits from a slightly tougher edge on the first pass, and wall-thickness variation that can change chip load mid-cut.

For reference, C36000 free-cutting brass sets the 100% machinability benchmark for copper alloys. C83600 doesn't quite reach that mark since its as-cast grain structure is coarser than wrought brass bar, but it still machines dramatically easier than lead-free bronzes, plain brasses, or copper.