Active Atom

Active Atom Materials - Tool Steel Group

There are six groupings of machine tool steel.

Active Atom utilizes them all, we manufacture tooling for the consumer products we produce here and we produce micromachining fixtures for other manufacturers. The requirements vary depending on the application of the tools to be made.

The grades of tool steel we precision machine are from the two U.S. Specification and Certification organizations AISI American Iron and Steel Institute and SAE Society of Automotive Engineers.

The Six Tool Steel Groups:

"W" - Water-Hardening

The "W" class steels are the more popular tooling steels, they are water quenched, can achieve a Hardness Rockwell of HRC 66 or greater they are brittle due to the hardness, not for high temperatures they can crack during water quenching.
The alloying process adds toughness utilizing Manganese Mn, Molybdenum Mo, Silicon Si, Vanadium V


This class of tool steel achieves high hardenablity and wear resistance, average toughness and heat softening resistant. The class has a high machinability rating for the “O” and “A” class, the “D” class has a low machinability rating because of the high carbon-chromium alloying. The “O” oil quenching and “A” air-hardening reduces distortion and the stresses brought on from “W” water quenching.

"O" - Oil-Hardening

Quenched and tempered tool steels.


Utilized for gauges cutting tools and knives this can be Hardness Rockwell to HRC 66 though the most common Hardness Rockwell is HRC 61 to HRC 63.
Carbon C 0.90% Manganese Mn 1.00% to 1.40%, Chromium Cr 0.50%, Tungsten W 0.50%, Silicon Si 0.30%, Vanadium V 0.20% (optional)


Utilized the same as O1 for gauges cutting tools and knives this can be Hardness Rockwell to HRC 66, the most common Hardness Rockwell is HRC 61 to HRC 63.
Carbon C 0.90% Manganese Mn 1.50% to 2.00%, Chromium Cr 0.30%, Silicon Si 0.30%, Vanadium V 0.15% (optional)


Cold work oil-hardening graphitic, exhalant for metal on metal sliding resilient to wear and galling, serious tool steel for master gauges, thread gauges, arbors, bushings, sleeves, cams, punches, dies, etc.
Carbon 1.45% Manganese Mn 1.00%, Silicon Si 1.00%, Molybdenum Mo 0.3%

"A" - Air-Hardening, Medium Alloy

Machinability is good, low distortion during heat treat due to high chromium alloy, high wear resistance and toughness.


General purpose tool steel, utilized for blanking, rolling dies, forming dies and thread rolling dies,etc.
Carbon 1.00%, Manganese Mn 1.00%, Chromium Cr 5.0%, Nickel Ni 0.3%, Molybdenum Mo 1.00%, Vanadium V 0.15% to 0.50%


Carbon 1.25%, Manganese Mn 0.5%, Chromium Cr 5.0%, Nickel Ni 0.3%, Molybdenum Mo 0.9% to 1.4%


Carbon 1.00%, Manganese Mn 2.00%, Chromium Cr 1.0%, Nickel Ni 0.3%, Molybdenum Mo 0.9%1.4%


This tool steel air-hardens at a low temperature about the same as the oil-hardening types, it is dimensionally stable, and this tool steel has a high stability, not wear resistant tool steel. Utilized for dies, forming tools and gauges.


Carbon 12.0% to 2.85%, Manganese Mn 0.8%, Chromium Cr 5.0% to 5.75%, Nickel Ni 0.3%, Molybdenum Mo 0.9% to 1.4%, Vanadium V 3.90% to 5.15%, Tungsten W 0.5% to 1.5%


Carbon 0.5% to 0.6%, Manganese Mn 0.5%, Chromium Cr 4.75% to 5.50%, Nickel Ni 0.3%, Molybdenum Mo 1.15% to 1.65%, Tungsten W 1.0% to 1.5%


Carbon 0.5%, Manganese Mn 0.5%, Silicon Si 0.95% to 1.15%, chromium Cr 4.75% to 5.00%, Nickel Ni 1.25 % to 1.75%, Molybdenum Mo 1.3% to 1.8%, Vanadium V 0.8% to 1.4%


Grade A10 contains uniform distribution of graphite particles to increase machinablity, provides self lubricating properties.
The A10 is utilized for gauges, arbors, shears and punches.
Carbon 1.25% to 1.50%, Manganese Mn 1.6% to 2.1%, Silicon Si 1.0% to 1.5%, Nickel Ni 1.55% to 2.05%, Molybdenum Mo 1.25% to 1.75%

"D" - High-Carbon, High Chromium

Good slide resistance in metal to metal contact this is a low cost metal in relation to other steels, the D2 is a good wear resistance and toughness it is good for food processing knives, shear blades and industrial cutting tools.
Carbon C 1.50%, Manganese Mn 0.30%, Silicon Si 0.30%, Chromium Cr 12.00%, Molybdenum 0.75%, Vanadium V 0.90%

"S" - Shock-Resistant


Tool steel “S” is a very high impact shock load applications, is good for both hot (up to 1000 Degree Fahrenheit and cold work in gripper dies punches and chisels. Not good for heat treating.
Cabon C 0.50%, Manganese Mn 0.75%, Silicon Si 0.25%, Chromium Cr 3.25%, Molybdenum Mo 1.40%

High Speed Steel (HSS)


"T" tungsten based
"M" molybdenum based
We do use high speed tool steel, but only to make specialized cutters for our machine tools, there are a lot of types, grade, strengths, toughness choices and we found a great place to learn more about these metals here at

"H" - Hot-Work

H1 through H19 (Chromium Based)

Chromium Cr content 5%

H20 through H39 tungsten based

Tungsten W content 9% to 18%

H40 through H59 molybdenum based

Tough as nails these tool steel are full of the toughest high percentages of alloys Tungsten, Vanadium, Chromium, Molybdenum.
We can but do not currently utilizes these steels though the future is full of opportunities.

Special Purpose

"P" - Plastic Mold Steels

Specialized for mold making we do not make molds.

"L" - Low Alloy

L2, L3, L6

"F" - Carbon Tungsten

F1, F2, F3
We do not see production of this steel in the USA, it might be available in China and Japan.