Stainless Steel 420 Rectangular Bar 6" x 3/8" Retail Price

About 420|A higher-carbon version of 410 (0.30-0.40% C vs 0.15% max for 410). Heat treats to HRC 50-55, making it the standard for plastic injection mold cavities, surgical instruments, and cutlery. In the annealed condition it machines well for a stainless, significantly better than 304. After hardening, plan on grinding or EDM for final dimensions. Corrosion resistance is fair when hardened and polished but degrades if the surface is rough or the part isn't passivated. Compare to 410 (lower hardness, better corrosion resistance) and 440C (even higher hardness, more carbon, slightly better corrosion resistance).

About Rectangular Bar|Solid rectangular cross-section stock. Functionally similar to flat bar but typically available in thicker, chunkier profiles. The naming varies by supplier — what one calls rectangular bar, another calls flat bar. Used for keys, gibs, wear strips, brackets, and any part where a rectangular starting profile saves setup time versus milling from plate.