Engineering · Machining guide
How to machine A2 tool steel.
A2 is the air-hardening tool steel used for die work, punches, gages, and fixturing components that need to be hardened to 56–62 HRC. Standard process: rough and finish-machine in annealed condition (~22 HRC), heat-treat to spec, then grind or wire-EDM final critical features. This guide covers the parameters and the practical sequencing decisions.
01 · Process sequence
Machine annealed, then heat treat.
A2 ships in annealed condition (~22 HRC). Standard practice is to rough and finish-machine in this state, then send out for the air-hardening cycle (austenitize 950–980 °C, air quench, double-temper to spec hardness). Post-heat-treat operations are restricted to grinding, wire EDM, or hard turning with CBN — milling above ~50 HRC isn’t productive.
Distortion during heat treat is small for A2 (it’s air-hardening, not oil-quenched), typically 0.001–0.002″ per inch. For tight-tolerance dies and gages, leave 0.005–0.010″ finish stock to clean up after heat treat. For most fixture work, the as-quenched dimensions are within standard tolerance.
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 | 0.002–0.003 IPT |
| Drilling | Solid carbide | 60–100 | 0.004–0.008 IPR |
| Tapping | HSS or carbide | 20–30 | — |
03 · Hardened operations
Above 50 HRC — grinding or EDM.
- Wire EDM is the right answer for sharp inside corners and tight slots.
A2 at 60 HRC cuts at the same rate as soft material on wire EDM. Inside corner radius limited only by wire diameter. The standard for stamping-die cavities and punch profiles. See our Wire EDM deep-dive.
- Surface grinding for flat, parallel surfaces.
For die plates, gage faces, fixture references — surface grinding holds 0.0001″ flatness and 8 µin Ra finish on hardened A2.
- CBN hard-turning
For cylindrical features in hardened A2 — punches, dowel pins, mandrel components. CBN at 350–450 SFM with 0.003–0.005 IPR. Surface finish 16 µin Ra achievable.
- Don’t mill above 50 HRC.
Carbide chips quickly, surface finish degrades, tool life is uneconomical. The combination of grinding + wire EDM covers nearly all features.
04 · A2 vs D2 vs H13
When to specify which tool steel.
- A2: general-purpose air-hardening. Good toughness, modest wear resistance. Default for fixture and tool work.
- D2: high-chromium die steel. Better wear resistance than A2 but more brittle and harder to machine. See D2 machining guide.
- H13: hot-work tool steel. For die-casting cores, forging dies, and components running at elevated temperature.
Keep exploring
Related tools & references
Mechanical properties, UNS, specs, and machinability at a glance.
Convert these SFM and IPT figures into spindle RPM and feed rate.
Recommended chip load by tool diameter for tool steel.
A2 density for part weight and stock estimates.
Compare A2 against D2, H13 and other tool steels.
Technically reviewed by the True Precision Machining engineering team · Last reviewed June 2026
Need A2 tool steel parts machined?
Send your drawing — A2 tool steel is a material we run regularly. Aerospace, medical, and defense work welcome.
Quotes in 24 hours