O1 is easier to heat-treat than many other low alloy steels. Its austenitizing requirements are like those of other low-alloy steels. It is also easy to quench to full hardness with slow oil. It is not easy to anneal but is suitable for most applications. The alloying elements, such as tungsten and vanadium, contribute to the material's hardness.

From 1894, higher chromium and tungsten content were explored. This eventually led to the first high-speed steel, 4% Cr 18% W. In contrast, O1 looks more like the steels of the earlier 1890s, which were not specifically designed for high-speed applications. Its composition isn't reported until 1925, but it is difficult to say how much changed during this period. And it isn't entirely clear how O1 came to be shaped in the first place.

The O1 began as an oil-hardening steel known as ketos. This steel was developed by John A. Mathews. Halcomb Steel then built a factory near Crucible's factory in Syracuse, New York. The two companies merged and subsequently gave it the AISI designation O1.

Most tool steels are supplied in the annealed or 200/250 Brinell condition with most of their alloy content present as alloy carbides. To develop these properties, the tool steels need to be heat-treated. The heat-treating process alters the alloy distribution of the material and converts a soft matrix into a tough matrix that can withstand pressure. Each step of the process has a specific purpose, and the final product is only as strong as the weakest part.

The O1 heat treatment process requires oil quenching. The process also produces tool steel with good wear resistance. Because of this, O1 tool steels are often used for general purpose applications. Their hardness and wear resistance make them ideal for cutting tools. Generally, this tool steel is also suitable for applications where alloy steels do not provide sufficient hardness or durability. You can also use O1 tool steel for blanking dies and bolster dies.