Wexmar handles tool steel CNC machining in A2, D2 and O1 for die components, wear parts, gauges and fixture details. These three cold work grades cover most shop tooling needs: O1 is an oil hardening grade that is easy to work, A2 is an air hardening grade with good size stability, and D2 is a high carbon, high chromium grade with strong wear resistance. We machine them annealed in Canastota, New York, send them out for hardening, and grind critical surfaces in-house after treatment.
Machinability of A2, D2 and O1
All three are machined in the annealed condition. Approximate machinability ratings against AISI 1212 at 100 are about 45 for O1, 42 for A2 and 30 for D2. The spread reflects carbide content. D2 carries a large volume of hard chromium carbides that behave like abrasive grit against the tool, so it wears tools noticeably faster than A2 or O1 even at the same hardness reading.
Tolerances and finish before and after hardening
In the annealed state, typical milled and turned tolerances are plus or minus 0.001 in, with 63 Ra typical on milled faces and 32 Ra on turned diameters. Because tool steels change size and shape slightly during hardening, critical dimensions are left with grind stock and brought to size after treatment on our surface and centerless grinders. Final tolerances and finishes on ground features depend on part size and geometry, and we confirm them at quote review. These are typical values, not guarantees.
Tool steel machining gotchas
- Decarburized skin. Hot rolled and annealed tool steel bar has a soft, decarburized surface layer. If it is not fully removed, the finished part will not reach full hardness at the surface.
- Abrasive wear in D2. D2 dulls edges quickly. We use wear-resistant coated carbide, keep speeds moderate, and change inserts on schedule rather than waiting for finish to degrade.
- Size change in hardening. A2 and D2 grow slightly and fairly predictably when air hardened. O1 moves more because it is oil quenched. Grind allowance is sized for the grade and the part.
- Stress relief. Heavy roughing leaves stress in large die blocks. For thin or long parts, a stress relief after roughing and before finish machining reduces distortion at hardening.
- Sharp corners. Unradiused internal corners are crack starters during hardening. We flag them and recommend radii where function allows.
Heat treat and finish options
Hardening, tempering, vacuum heat treat and cryogenic treatment are performed through qualified outside processors to the hardness on the drawing, typically in the high 50s to low 60s HRC for these grades. Coatings such as nitriding, black oxide and PVD wear coatings are also sourced outside. After heat treat, we surface grind or centerless grind the functional features and verify them on our CMMs.
Common A2, D2 and O1 parts
- Punches, die buttons and stripper inserts for stamping dies
- Wear plates, guide rails and gibs milled on horizontal machining centers
- Shear blades, slitter knives and trim steels
- Go/no-go plug gauges, setting masters and locating pins turned and ground
- Forming tools, bending dies and fixture locators
Round punches and pins are turned on our lathes or Swiss-type machines, then ground. Blocks and plates run on our horizontal milling centers, where multiple faces can be machined in one setup before hardening.
Cost index for cold work tool steels
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Reference |
| 4140 annealed | ~66 | 1.6 | Lower cost where wear is moderate |
| O1 annealed | ~45 | 2.5 | Oil hardening, easy to work |
| A2 annealed | ~42 | 2.5 | Air hardening, stable size |
| D2 annealed | ~30 | 2.5 | High wear resistance, abrasive to tools |
| S7 / H13 annealed | ~45 | 2.6 | Shock and hot work grades |
The index is typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing, and D2 often runs above the index on tool-intensive parts.
Applications and industries
Stamping and metal forming shops, packaging machinery builders, fastener manufacturers, and industrial OEMs that maintain their own tooling all use cold work tool steel components. We supply replacement punches, die sections and wear parts built to print, as well as gauges for incoming inspection. If a part sees impact or heat instead of pure abrasion, the S7 and H13 tool steel page covers those grades. Our inspection and quality page explains how hardened features are verified with CMM reports.
Getting a quote
For A2, D2 or O1 tooling details, upload a drawing for an instant estimate or call (315) 400-2654. A human estimator confirms every quote, including heat treat routing and grind allowance.