sae 10b21 steel properties the right material: | Feature | SAE 10B21 | SAE 1018 | 4140 Alloy Steel | |---------|-----------|----------|------------------| | Machinability | Excellent | Good | Moderate | | Strength | Moderate | Moderate | High | | Hardness | Up to 120 R Reginald Konopelski Feb 2, 2026