Engineering · Machining guide
How to machine D2 tool steel.
D2 is the high-chromium die steel for stamping punches, forming dies, and wear-resistant components. The 12% chromium content gives outstanding wear resistance after heat treat — and makes D2 noticeably tougher to machine than A2 even in annealed condition. Hardened D2 (60+ HRC) is wire-EDM and grinding territory only.
01 · Why D2 is harder than A2
Chromium carbides.
D2 contains 11.5–12.5% chromium and 1.4–1.6% carbon, which form coarse chromium carbide particles even in the annealed condition. Those carbides are the source of D2’s wear resistance — and the source of its machining difficulty. The carbides abrade carbide cutting tools rapidly. Tool life on D2 is roughly 60% of A2 at the same hardness.
The standard process is the same as A2: rough and finish in annealed (~25 HRC), heat-treat to 60+ HRC, then wire EDM or grind for final critical features. Like A2, D2 is air-hardening and dimensional change through heat treat is low (~0.0005 in/in) — any slightly higher size change versus A2 comes from D2’s higher carbide volume and retained austenite, not the quench.
02 · Cutting parameters — annealed
Slower than A2, smaller chip loads.
| Operation | Tool | SFM | IPT / IPR |
|---|---|---|---|
| Roughing turn | Coated carbide | 50–100 | 0.008–0.014 IPR |
| Finishing turn | Coated carbide | 80–150 | 0.004–0.008 IPR |
| End mill (rough) | Solid carbide | 50–100 | 0.002–0.004 IPT |
| End mill (finish) | Solid carbide | 80–150 | 0.001–0.003 IPT |
| Drilling | Solid carbide | 40–80 | 0.003–0.006 IPR |
| Tapping | Carbide forming | 10–20 | — |
Subtract another 15% SFM if you’re running pre-hardened D2 (some suppliers sell D2 in pre-hardened ~58 HRC condition for fixture use). At that hardness, plan around CBN tooling or accept very short tool life.
03 · Hardened operations
Wire EDM dominates.
- Wire EDM is the production tool for hardened D2.
Stamping-die cavities, punch profiles, blanking-die geometry. D2 at 60 HRC cuts on wire at the same rate as soft material — the chromium carbides don’t affect EDM the way they affect carbide tooling. See our Wire EDM deep-dive.
- Surface grinding for plate flatness.
CBN wheels for hardened D2 — aluminum-oxide wheels load up quickly. Holds 0.0001″ flatness and 8 µin Ra at production rates.
- CBN hard-turning
Possible for cylindrical features but slower than wire EDM. CBN at 250–350 SFM with very small DOC (≤0.005″).
- Don’t mill hardened D2.
Carbide tools chip rapidly even on light cuts. Wire EDM or grinding only for hardened operations.
Keep exploring
Related tools & references
High-chromium die steel properties and hardness data.
Set conservative SFM for annealed D2 work.
Per-tooth chip loads for abrasive tool steels.
Stock and finished-part weights for D2 plate.
Compare D2 against A2 and H13 tool steels.
Technically reviewed by the True Precision Machining engineering team · Last reviewed June 2026
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