TS · 10 grades
Tool Steels
Steels bought for what they do after hardening, not before.
Tool steels exist to hold an edge, resist wear or survive a thermal cycle, and they only reach that state after heat treatment - which means the sequence machine → harden → grind is part of the design, not an afterthought. A2 and D2 cover most cold-work needs, H13 covers hot work and die casting, and M2 is where you need hardness and wear resistance at temperature.
What this family does well, and where it bites
- Hardened to 45–62 HRC, then ground or hard turned to final size
- Distortion is expected: leave stock and grind after heat treatment
- Wear resistance comes at the cost of toughness - pick the balance deliberately
- EDM and jig grinding handle features that cannot be milled after hardening
Industries served
- Tooling & Mould Making
- Automotive & EV
- Industrial Equipment
- Packaging
- Consumer Products
Tool Steels grades we machine
Each grade page carries the properties as supplied, what heat treatment does or does not do to it, the achievable surface finish, starting cutting parameters and the DFM notes that matter for that specific grade.
A2
5/1058–60 HRC hardened · ~217 HB annealed · Not rated in tension at 58–60 HRC - tool steels are specified by hardness and wear behaviour
The safe general-purpose tool steel.
D2
4/1058–62 HRC hardened · ~217 HB annealed · Not rated in tension at 58–62 HRC
Annealed it machines reasonably but it is abrasive on the tool because of the chromium carbides.
D3
4/1058–62 HRC hardened · ~226 HB annealed · Not rated in tension at 58–62 HRC
More carbon and more carbide than D2, so more wear resistance and less toughness - and slightly harder to machine and grind in the annealed state.
O1
5/1060–64 HRC hardened · ~212 HB annealed · Not rated in tension at 62 HRC
A classic oil-hardening tool steel: machines well in the annealed state, hardens to 60–64 HRC, and needs a careful quench because it moves more than an air-hardening grade.
H13
5/1048–52 HRC hardened · ~197 HB annealed · 1,590 MPa typical at 48 HRC (tool steels are specified by hardness and hot strength)
The hot-work die steel, and the one that gets the most use in this shop for aluminium die-casting tooling.
P20
6/1028–32 HRC as supplied · 52 HRC nitrided surface · 1,000 MPa typical
Supplied pre-hardened at 28–32 HRC, so it machines like a tough alloy steel rather than a tool steel.
S7
5/1055–57 HRC hardened · ~200 HB annealed · Not rated in tension at 56 HRC; specified for impact toughness
The toughness grade.
M2
3/1060–65 HRC hardened · ~230 HB annealed · Not rated in tension at 64 HRC; specified for hot hardness and wear
High speed steel: hard (60–65 HRC), abrasion resistant and unpleasant to machine in any state.
L6
5/1055–58 HRC hardened · ~200 HB annealed · Not rated in tension at 57 HRC
A tough oil-hardening tool steel sitting between O1 and S7: decent wear resistance with more shock tolerance than either D2 or O1.
52100
4/1060–66 HRC hardened · 183–217 HB annealed · 2,500 MPa compressive strength at 62 HRC (rated for rolling contact, not tension)
The through-hardening bearing steel: machines acceptably in the spheroidise-annealed condition, then hardens to 60–66 HRC for rolling contact service.
Questions buyers ask
- Why does a hardened part cost more when it is the same shape?
- Because it takes two operations where a soft part takes one, plus a heat-treat trip. Machine oversize, heat treat, then grind to size - and the grinding is slower than the milling it replaces. On a simple flat plate that can look like a 60% premium for the same outline.
- A2 or D2?
- A2 is the safer default: it moves less in the quench, so a complex pocketed part keeps its dimension. D2 holds an edge longer against abrasive wear but distorts more and is harder to grind cleanly. If the tool sees abrasive filled plastics, D2; if it is a fixture, A2.