Hardenable.
Wear-resistant.
Up to 62 HRC.

4140 is the workhorse: lower cost, easier to machine, adequate for most high-strength applications. 4340 contains nickel which improves hardenability and toughness — specify when the part needs tough-at-depth properties (thick sections, high stress) or for aerospace critical applications where fatigue performance matters. 4340 is approximately 1.3× the cost of 4140.

We perform hardening, tempering, stress relief, and light case hardening in-house on most alloy and tool steels. Specialty treatments (vacuum hardening, deep cryogenic treatment, plasma nitriding) are outsourced to qualified partners. All heat treatment documented with process records for aerospace and automotive orders.

Yes. We routinely hard-mill and hard-turn D2, H13, and A2 up to 62 HRC using CBN (cubic boron nitride) and carbide tooling. For features below 0.005 mm tolerance on hardened steel, grinding or EDM is used instead of direct machining.

Pre-hardened: delivered from the mill in mid-range hardness (e.g., 4140 at 28–32 HRC). Machine to final shape — no distortion or grinding needed. Used when mid-range hardness is adequate. Through-hardened: machine slightly oversized, then heat-treat to full hardness (55+ HRC), then grind to final tolerance. Used when maximum hardness is required; requires grinding allowance (typically 0.2–0.5 mm per surface).

Tool steel when: wear is the primary concern (cutting, forming, dies), part needs hardness above 55 HRC, application involves elevated temperature service (hot-work). Alloy steel when: primary concern is tensile or yield strength, hardness of 28–45 HRC is adequate, part is structural rather than wear-critical. Alloy steels are 2–3× cheaper than most tool steels.