About 304|The most common stainless steel, period. 18% chromium, 8% nickel, good corrosion resistance, excellent weldability. The downside is it's not fun to machine. It work hardens fast, produces long stringy chips that wrap around everything, and will eat tools if you let it rub instead of cut. The key is sharp carbide, aggressive chipload, moderate speed, and flood coolant. Keep the tool cutting, not rubbing. Quality varies batch to batch. Some runs cut clean, others feel like chrome bumper. Carpenter Project 70 and similar premium melts are worth the upside if you're running volume. Used everywhere from food equipment to medical devices to architectural trim. Compare to
303 (way easier to machine but can't weld it) and
316 (better corrosion resistance, slightly gummier).
