Milling Stainless Steel 304 on CNC: Avoiding Work-Hardening & Tool Burning

Why Stainless Steel 304 Work-Hardens

Stainless 304 contains 18% chromium and 8% nickel. When subjected to mechanical friction or heat without continuous chip shearing, the surface molecular structure transforms into a hardened layer approaching HRC 50+.

The Golden Rules for Stainless Steel Milling

1. Never Dwell or Stop the Tool in Cut: Always maintain positive forward feed.
2. Low Surface Speed (SFM): Run at 150 – 250 SFM with flood coolant or high-pressure mist.
3. Unequal Flute Spacing: Use 4-Flute variable helix end mills with heavy corner radiuses (0.5mm - 1.0mm) to prevent corner chipping.