Engineering · Machining guide
How to machine H13 tool steel.
H13 is the hot-work tool steel for die-casting cores, forging dies, plastic injection molds, and components running at elevated temperature. The chromium-molybdenum-vanadium alloying gives it red-hardness retention to ~540 °C and outstanding thermal-fatigue resistance. Standard process is the same as A2/D2: rough machine in annealed, heat-treat to spec, finish with grinding or wire EDM.
01 · H13 vs A2 vs D2
Hot-work, not cold-work.
A2 and D2 are cold-work tool steels — used at room temperature where wear resistance matters. H13 is a hot-work tool steel — used at elevated temperature where thermal fatigue and red-hardness matter. The alloying is different (5% Cr, 1.5% Mo, 1% V vs A2’s 5% Cr) and the tempering temperatures are higher. End hardness is typically lower (44–50 HRC for service vs 60+ HRC for A2 cold-work tools) because toughness matters more than peak hardness.
For machining purposes, H13 is slightly easier than A2 in the annealed state and dramatically easier than D2 (which has chromium-carbide abrasion). Service hardness is also lower, which means hard-machining strategies can include conventional milling at the lower hardness range — though wire EDM is still standard for sharp internal features.
02 · Cutting parameters — annealed
Standard tool-steel feeds and speeds.
| Operation | Tool | SFM | IPT / IPR |
|---|---|---|---|
| Roughing turn | Coated carbide | 200–300 | 0.010–0.018 IPR |
| Finishing turn | Coated carbide | 300–400 | 0.005–0.010 IPR |
| End mill (rough) | Solid carbide | 200–300 | 0.003–0.006 IPT |
| End mill (finish) | Solid carbide | 300–400 | 0.002–0.004 IPT |
| Drilling | Solid carbide | 70–100 | 0.004–0.008 IPR |
| Tapping | HSS or carbide | 20–30 | — |
| Hard mill (44 HRC) | Solid carbide | 100–150 | 0.001–0.002 IPT |
03 · Practical notes
Mold polish considerations.
- Tooling: coated carbide for annealed and 44 HRC. CBN or wire EDM above 50 HRC.
- Coolant: water-soluble flood. EP additives helpful but not required for annealed work.
- Mold polish surface finish: for plastic injection molds, surface finish below 4 µin Ra is often required for clean part release. Final polish operations (manual or vapor) follow milling — leave the surface clean enough to polish.
- Heat-treat sequence: rough in annealed → heat-treat to ~44 HRC → semi-finish → polish or grind. Heat-treat distortion is small (~0.001″/in for vacuum-hardened H13) — leave 0.005″ finish stock.
- Wire EDM for hardened details: sharp internal cavity features and ejector/core details are typically wire-EDM’d after heat treat. See Wire EDM deep-dive.
- Common AMS: 6408 (bar). H11 (AMS 6437) is closely related — slightly different chemistry (less vanadium, higher toughness), used for aerospace landing-gear arms and structural forgings.
Keep exploring
Related tools & references
Hot-work tool steel properties and hardness data.
Set SFM for annealed and pre-hardened H13.
Per-tooth chip loads for chromium tool steels.
Mold and die stock weights for H13 plate.
Compare H13 against A2 and D2 tool steels.
Technically reviewed by the True Precision Machining engineering team · Last reviewed June 2026
Standards referenced: AMS 6408, AMS 6437
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