O1 Tool Steel has been used since its creation in 1905 by the company Halcomb. The O in its name represents the ‘Oil Quenching’ which contributes to this steel’s impressive hardness.
And the 1 represents that this is the first in the line of O Steels, being the predecessor to O2, O3, etc.
The steel is generally considered to be more low range, but this does not compromise its quality, still being a popular choice for making tools, with knives being a particularly popular choice.
So let’s get into the chemical composition of O1 Tool Steel and then break down how each element contributes to the unique attributes of this knife-making component.
What Is The Chemical Composition Of O1 Tool Steel?
- 1% Carbon (C)
- 0.6% Chromium (Cr)
- 1.4% Manganese (Mn)
- 0.6% Tungsten (W)
- 0.5% Silicon (Si)
- 0.3% Vanadium (V)
- 0.03% Sulfur (S)
- 0.03% Phosphorus (P)
But what do these different elements of the steel mean?
The main factor that the carbon contributes towards is steel hardness. This is a very important factor for a knife steel as a hard blade has a better cutting ability. However, if too much carbon is used, it can degrade the steel’s toughness. Manganese also contributes to the blade’s hardness.
Chromium is included for a variety of reasons, as it can increase both the toughness and the hardness of a steel. It is also a perfect choice for knives as blades with chromium have better edge retention, and it can contribute to good corrosion resistance as well.
Tungsten is also largely included for its use in increasing edge retention, but as well as this, it helps a knife with wear resistance.
As well as its contributions towards steel hardness, Manganese also helps improve a steel’s machinability. Sulfur is also usually used for this purpose too.
Silicone and Phosphorus are both included to help with a knife’s strength and finally, Vanadium improves a steel’s wear resistance as well as its toughness.
Also, it is worth noting that because this steel has a below 12% content of chromium, it does not qualify as a stainless steel, therefore giving it its classification as a tool steel.
So how well does O1 Tool Steel score on its factors individually?
How Hard Is O1 Tool Steel?
On the HRC (Hardness Rockwell C) scale O1, steel usually scores an impressive 57, but this is variable to the heat treatment used on the steel or knife as it is made.
This is a good rating of hardness and if the steel is used in a knife, that means it will be able to do a variety of tasks that require a strong sharp knife.
How Tough Is O1 Tool Steel?
While not as tough as some more expensive steels used in knives, the O1 tool steel has a surprisingly good toughness for a lower-end steel and boasts impressive hardness.
Usually, with knife steel hardness, it comes at the sacrifice of toughness and vice versa because of the properties of key elements like carbon. But this knife steel manages to strike an impressive balance.
How Good Is The Wear Resistance Of O1 Tool Steel?
One of the best reasons to use O1 Tool Steel and one of the contributing factors to its maintained popularity is its excellent wear resistance.
By using a signature mix of carbon, vanadium, and manganese, this knife is great for its ability to survive most conditions and its resistance to any abrasions that can compromise the quality of a steel used for knives.
How Good Is The Corrosion Resistance Of O1 Tool Steel?
The main area in which the O1 Tool Steel lacks is in its corrosion resistance. Because of a slightly lower than average chromium content, if this steel is used in knives, it is very likely to face corrosion damage if in the correct conditions.
This can be avoided if you keep the blade oiled and keep an eye out for the first signs of rusting. However, if you know you will be largely using this steel in humid conditions, it is hard to recommend this steel.
How Good Is The Edge Retention Of O1 Tool Steel?
Because of the excellent hardness of this steel, if it is used in knives, they will have amazing edge retention. This means that if used in a blade, the steel will be able to keep a sharp edge even after a lot of use.
What Is The Machinability Of the O1 Tool Steel?
Largely due to the manganese content of the steel, O1 Tool Steel has a 90% machinability rating meaning that it is very easy for manufacturers to work with.
This is also a contributing factor to O1’s popularity with large-scale knife-makers who appreciate the ease at which they can use this steel and not have to worry about damaging their equipment.
How Easy Is It To Sharpen O1 Tool Steel?
In spite of the impressive hardness of the steel, if used in knives, it is a surprisingly easy blade steel to sharpen.
Because of the steel’s impressive edge retention, you will not have to be sharpening this blade all the time, however, when the time does arise, this steel is easy to sharpen without any specialist equipment.
Good Alternative Steels
A2: O1 is often compared to A2 Steel and is outclassed by it in terms of corrosion resistance because of higher chromium content, however, this makes A2 steel less accessible.
AISI L6: This steel is also often compared to O1 having similar accessibility, however, because of an increased nickel content it is generally tougher.
D2: This is an air-hardened steel option that has better corrosion resistance due to more chromium, however, it is significantly less tough than O1 Steel.
So Is O1 Tool Steel A Good Knife Steel?
If you plan to use O1 Tool Steel for knives, you are finding a very accessible yet impressive option.
If you are looking for an affordable blade with a good balance of hardness and toughness with good edge retention, this is a great classic choice.
Also, if you plan to use this steel to produce your own blades, its machinability makes it a good option.
However, if you know you are going to use this knife in humid or wet conditions, the lackluster corrosion resistance makes this knife steel a poor choice.
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