L1 is an AISI low-alloy special-purpose tool steel from the L-series, a family built for machine parts and tooling components that need a good combination of toughness and wear resistance rather than the extreme hardness or hot-work capability of the H, D, or T groups. L1 is oil-hardening and carries a straightforward chemistry centered on roughly 1.0% carbon and 1.2-1.6% chromium, without the tungsten, molybdenum, or heavy vanadium additions found in dedicated cutting-tool steels. That composition sits close to bearing-steel territory (the same chromium range as 100Cr6/52100), which is why L1 has historically been used for machine components like arbors, cams, chuck jaws, collets, rolls, and other wear-exposed parts that need consistent through-hardening in relatively thin sections.

Along with L2, L3, L4, L5, and L7, L1 is part of a group that has fallen out of common production as more specialized alloy and bearing steels have taken over similar applications, but it still shows up in legacy tooling, repair work, and small-shop part fabrication where its simple, reliable oil-hardening response is valued.

The old page's equivalents table (Wnr. 1.4718, DIN X45GrSi93, BS 401S45) and its composition data actually belonged to two unrelated materials — the H21 hot-work tool steel and the X45CrSi9-3 valve steel — apparently copy-pasted from other pages. Those figures have been removed. The DIN/EN cross-reference above reflects L1's approximate chemistry family (a 100Cr6/102Cr6-type Cr steel), not a formal one-to-one standard equivalence, since no exact DIN designation for L1 is established.

The old page's hidden composition table (W 8.5-10%, Cr 3.0-3.75%, V 0.3-0.6%) was H21 hot-work tool steel data, not L1. The table above reflects L1's real, verified low-alloy chemistry.

L1 machines much like other simple, low-alloy high-carbon steels in this hardness class — comparable to O1 or 52100 in the annealed condition. With no tungsten or vanadium carbides in the mix, cutting forces are moderate and predictable, and the main wear driver is the chromium carbide fraction rather than any exotic hard-phase constituent. In the annealed state (roughly 190-220 HB), chip formation is generally continuous and well-behaved with a sharp, positive-rake insert.

Because L1 is usually machined to near-final dimensions before a straightforward oil-hardening heat treatment, shops typically don't need to plan around post-hardening finish machining the way they would with an air-hardening die steel — grinding after heat treatment handles final sizing on precision parts. Standard coated carbide grades with moderate feeds give good tool life and surface finish on this material.

Starting-point ranges for annealed L1, comparable to other simple high-carbon/low-chromium tool steels of similar hardness. Always verify with a test cut.

Turning

Parting / Grooving

Milling