Hardness Conversion Table (Non-Austenitic Steels)
Per ASTM E140. HRC = Rockwell C, HB = Brinell 3000 kg, HV = Vickers, HS = Shore Scleroscope.
| HRC | HRC (alternate) | HB | HV | HS | Typical Material |
|---|---|---|---|---|---|
| 65 | 64.5 | — | 880 | 100 | Carbide tooling |
| 62 | 62.0 | — | 800 | 95 | Hardened D2, H13 |
| 60 | 60.0 | — | 750 | 91 | Hardened tool steel |
| 58 | 58.0 | — | 700 | 87 | H13 at max hardness |
| 55 | 55.0 | 560 | 600 | 80 | Hardened H13, A2 |
| 52 | 52.0 | 510 | 550 | 75 | Pre-hardened tool steel |
| 50 | 50.0 | 480 | 510 | 72 | Medium-hard tool steel |
| 48 | 48.0 | 460 | 480 | 69 | |
| 45 | 45.0 | 430 | 440 | 65 | H13 (45 HRC typical) |
| 42 | 42.0 | 400 | 410 | 61 | |
| 40 | 40.0 | 370 | 380 | 58 | Harder alloy steel |
| 38 | 38.0 | 350 | 360 | 55 | |
| 35 | 35.0 | 330 | 340 | 52 | |
| 32 | 32.0 | 300 | 310 | 48 | |
| 30 | 30.0 | 285 | 290 | 46 | P20 (pre-hardened) |
| 28 | 28.0 | 270 | 275 | 44 | |
| 25 | 25.0 | 255 | 260 | 41 | 4140 (quenched) |
| 22 | 22.0 | 235 | 240 | 38 | 4140 (annealed) |
| 20 | 20.0 | 220 | 230 | 36 | |
| 18 | 18.0 | 210 | 215 | 34 | |
| 15 | 15.0 | 195 | 200 | 31 | |
| 12 | 12.0 | 180 | 185 | 28 | |
| 10 | 10.0 | 170 | 175 | 26 | |
| 8 | 8.0 | 160 | 165 | 24 | 1045 steel |
| 5 | 5.0 | 145 | 150 | 22 | 1020 steel |
| 0 | 0 | 135 | 140 | 20 | Mild steel |
Quick Reference for Common DHD Materials
| Material | Typical Hardness | HRC | HB | Machinability |
|---|---|---|---|---|
| 1020 carbon steel | Annealed | 0–5 | 135–145 | Good |
| 1045 carbon steel | As-rolled | 8–12 | 160–180 | Fair-good |
| 4140 alloy steel | Annealed | 22–25 | 235–255 | Fair |
| 4140 alloy steel | Q&T | 25–35 | 255–330 | Poor |
| 4340 alloy steel | Annealed | 22–25 | 235–255 | Fair |
| P20 mold steel | Pre-hardened | 28–32 | 270–300 | Fair-good |
| H13 tool steel | Annealed | 20–25 | 220–255 | Fair |
| H13 tool steel | Hardened | 45–55 | 430–560 | Poor |
| A2 tool steel | Hardened | 57–62 | 600–700 | Very poor |
| D2 tool steel | Hardened | 58–64 | 600–750 | Extremely poor |
| S7 tool steel | Hardened | 48–58 | 460–600 | Poor |
| 304 stainless | Annealed | 0–5 | 135–175 | Fair |
| 316 stainless | Annealed | 0–5 | 135–175 | Fair |
| Ti-6Al-4V | Annealed | 33–36 | 310–340 | Poor |
| Inconel 718 | Solution treated | 34–38 | 330–360 | Very poor |
| Inconel 718 | Aged | 40–47 | 370–470 | Extremely poor |
| Aluminum 6061-T6 | T6 | 0 | 95–100 | Excellent |
| Aluminum 7075-T6 | T6 | 0 | 150–160 | Excellent |
Application Notes
- HRC > 55: Deep hole drilling requires AlTiN/AlCrN-coated carbide or PCBN tooling. Expect tool life reductions of 50–75%.
- HRC 35–55: TiAlN-coated carbide works with reduced speeds. Coolant pressure ≥ 60 bar recommended.
- HRC < 35: Standard carbide gun drilling is effective.
- NACE MR0175 (sour gas): Limits carbon steel hardness to ≤ 22 HRC to prevent sulfide stress cracking.
Source: ASTM E140-12B(2019)e1; ISCAR Die & Molds Guide; multiple manufacturer data.