About 510|Phosphor bronze A (95% copper, 5% tin, trace phosphorus). The standard phosphor bronze. Excellent spring properties, fatigue resistance, and corrosion resistance. This is the spring clip, bellows, and electrical connector alloy. Machines poorly — it’s tough, work-hardens rapidly, and produces long stringy chips that wrap around everything. If you must machine it, use sharp carbide, aggressive feeds, and flood coolant. Available mainly in sheet, strip, wire, and rod. In the shop, you’ll usually see it being formed, not cut. Compare to
544 (same family, free-machining version with lead) and 260 cartridge brass (easier to form but weaker spring properties).
