Tool Steel Machining

DEK has done tool steel machining since 2002: A2, D2, H13, O1, S7 and A3, annealed or hardened to 60+ HRC, held to ±0.005 mm. Hard milling, wire EDM and grinding in-house, no MOQ.

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±0.005mm
Machined Tolerance
60+ HRC
Hardened Machining
2002
Mold Component Roots

ISO 9001:2015 Certified AS9100D and ISO 13485 certified

Why Tool Steel Machining Starts at DEK

DEK started in 2002 making core pins, ejector pins and guide bushes for mold tooling. Tool steel is one of the steel families in our CNC metal machining range, used when a part cuts, forms or wears against another hard surface, or must hold a sharp edge.

Do not specify it by habit: a 4140 alloy steel at 28–36 HRC is cheaper, tougher and simpler to machine for shafts and fixtures that do not need 58 HRC, and 440C stainless is better where a hardened part sees moisture.

ISO 9001:2015, ISO 13485, AS9100D by TÜV
EDM and grinding in-house after hardening
Engineer-reviewed quotes within 6 hours
No MOQ; prototypes in 3–5 days

Two cylindrical machined metal bushings on white

Tool Steel Grades We Machine

Six grades, machined annealed or hardened. Machinability ratings are relative to AISI 1212 free-machining steel, annealed stock.

A2
57–62 HRC hardened
General cold-work dies with good dimensional stability; air quench, +0.03 to +0.10% size change.
D2
58–62 HRC; ~30–35% machinability
Abrasive wear: blanking dies, slitter knives. 12% Cr carbides dull edges, so D2 needs rigid setups.
H13
44–52 HRC hardened
Hot work: extrusion tooling, hot-running mold inserts. H13 machining runs annealed, then hardened; H13 keeps roughly 40 HRC at 500 °C.
O1
~55–60% machinability
Gauges and small punches where cost matters more than distortion; O1 is oil quenched to 57–62 HRC.
S7
54–58 HRC hardened
Shock loads: chisels, shear blades, heavy punches. S7 is air quenched, oil on heavy sections.
A3
58–63 HRC hardened
1.25% C, 5% Cr, 1.1% Mo, 1% V; ≤235 HB annealed and ~40–45% machinability. See the A3 page.

Hard milling hardened tool steel die block on CNC mill

±0.003mm
Ground diameters
0.005 mm
Ground flatness
Ra 0.2µm
Best ground finish

Hardened Steel Machining at DEK

Annealed parts are roughed, heat treated, then finished; hardened blanks go straight to hard milling, wire EDM and grinding.

1

Annealed CNC Milling

At 200–255 HB all six grades cut with coated carbide. CNC milling on 3-, 4- and 5-axis machines handles blocks up to about 1000 mm.
2

Hard Milling

Machining hardened steel up to 60–62 HRC with CBN and fine-grain carbide, small radial engagement and light chip loads; one heat-treat cycle removed.
3

Wire EDM

Wire EDM cuts D2 punches and die sections to ±0.005 mm, Ra 0.4 µm on skim passes; internal corners limited by 0.1–0.25 mm wire.
4

Precision Grinding

Surface, cylindrical and jig grinding: 0.005 mm flatness, ±0.003 mm on punch shanks, Ra 0.2–0.4 µm.

Distortion and Stock Planning Tips

Size change on hardening is planned into the program, grade by grade, before the first cut.

1

Grind Stock by Grade

We leave 0.15–0.25 mm per face on A2 and A3, 0.2–0.3 mm on D2, H13 and S7, and 0.3–0.5 mm on O1, which moves +0.10 to +0.20% in the oil quench.
2

Cut Before Hardening

Threads, cross holes and H13 cooling channels are machined annealed; jig-ground holes are drilled undersize and tempering is completed before finish work.
3

D2 Directional Movement

D2 grows +0.05 to +0.10% and can move directionally, so it gets the 0.2–0.3 mm per face allowance and a rigid setup from roughing onward.
4

Verified Hardness and Grade

Rockwell test on every heat-treated lot; material certificates matched to a spectrometer check so a D2 order never ships in a look-alike grade.

Tool Steel Grades in Stock

Grade sheets for A2, A3, D2, H13, O1 and S7: equivalents, chemistry, annealed and hardened hardness, and typical parts for each.

When to Choose Tool Steel vs 4140 or 440C

Tool steel against the cheaper options the source names for parts that do not need 58 HRC, including 4340 alloy steel.

Criteria	This MaterialTool steel	4140	440C
Choose it for	Cutting, forming, wear	Shafts, fixtures	Hardened, wet parts
Hardness	Up to 60+ HRC	28–36 HRC	–
Cost	Higher	Cheaper	–
Toughness	Lower	Tougher	–
Moisture	–	–	Better choice

Typical Tool Steel Parts We Machine

Punches, dies, mold inserts and gauges for stamping, packaging machinery, automation and automotive tooling.

Finishing Options for Tool Steel Parts

CNC machining plus heat treatment, coating or polishing, coordinated by DEK on the parts we machine.

Treatments

Heat treatment
PVD coating
Black oxide
Polishing

Need nitriding for H13? Ask our engineers for a route.

Tool Steel Machining FAQ

Questions engineers ask about hardened, annealed and grade-specific work.

Can you machine hardened steel, or does it have to be annealed first?

Both. Annealed stock is milled and turned with carbide at normal parameters. Hardened stock up to 60–62 HRC is hard milled with CBN or fine-grain carbide, cut by wire or sinker EDM, or ground. For most dies and inserts we machine annealed, heat treat, then finish by grinding and EDM.

Which is easier, D2 steel machining or A2 tool steel machining?

A2. D2's 11–13% chromium forms large, hard carbides that abrade cutting edges; annealed D2 rates around 30–35% of 1212 free-machining steel, while A2 rates about 45–50%. D2 pays that back with roughly twice the abrasive wear resistance once hardened.

Can O1 be machined after hardening?

Yes, by grinding and wire EDM at 57–62 HRC. O1 tool steel machining is easiest annealed (about 55–60% of 1212), the standard route for gauges and small punches. Hardened O1 distorts more than A2 in the oil quench, so we leave 0.3–0.5 mm of stock.