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 | 330–490 | 0.008–0.014 IPR |
| Finishing turn | Coated carbide | 490–655 | 0.004–0.008 IPR |
| End mill (rough) | Solid carbide | 230–330 | 0.0008–0.0016 IPT |
| End mill (finish) | Solid carbide | 230–330 | 0.0008–0.0016 IPT |
| Drilling | Solid carbide | 230–295 | 0.003–0.006 IPR |
| Tapping | Carbide forming | 10–20 | — |
IPT (chip-load) values assume roughly ½–1″ end mills; scale down for smaller tools — see the chip-load chart.
Carbide speeds and end-mill chip loads are Uddeholm’s soft-annealed Sverker 21 (D2) data converted to inch units (end-mill IPT is their slot-milling value for 10–20 mm cutters; raise it for chip thinning at light stepover); start at the low end of each range. These values do not scale down to hardened stock: pre-hardened D2 (some suppliers sell ~58 HRC material for fixture use) needs CBN or hard-milling data from the tool maker, or very short tool life. On the same maker’s data, soft-annealed A2 (Rigor) runs roughly 5–20% faster than D2 and H13 (Orvar 2M) roughly 1.5–2.3× faster; our A2 and H13 tables are more conservative starting points.
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 5-axis wire EDMs.
- 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.
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