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  • It can be tough to decide on the most appropriate tool steel grade, like A2 vs O1, especially when there is no right or wrong overall answer. Instead, it helps to compare their qualities and discover their strengths and weaknesses. Once you know these, it’s much easier to decide on the most appropriate material for a specific project.


    In this article, we will be analysing A2 and O1 tool steels to provide you with the information you need to make the most suitable decision depending on your intended use. 


    What is A2 Tool Steel?

    A2 tool steel is an air-hardening steel, with the ‘A’ in the name representing this. It’s a cold work steel which means it is shaped below its recrystallisation temperature in contrast to the typical steelwork processes of hot rolling, forging, and welding. 


    A2 tool steel contains a small amount of Chromium – 5% to be exact. Adding this element to the alloy provides a high level of hardness; following heat treatments, the hardness values of A2 reach a range between 57-62 on the Rockwell Hardness Scale


    Chromium is added to turn steel into stainless steel; however, it must contain a minimum of 11-12% Chromium to be identified as stainless steel. While A2 is not a stainless steel, the 5% of Chromium does result in good wear and abrasion resistance, as well as good toughness. 


    Overall it is an easily machined steel grade that is capable of holding a good, sharp and durable edge. It is tough and has good wear resistance, making it a great all-rounder and a popular choice for many applications. 


    Chemical Composition of A2 Tool Steel


    ElementContent (%)
    C1.00
    Mn1.00
    Cr5.00
    Ni0.30
    Mo1.00
    V0.15-0.50

    Mechanical Properties of A2 Tool Steel


    Mechanical PropertiesMetricImperial
    Rockwell Hardness (C)6464
    Bulk Modulus140 GPa20300 ksi
    Machinability 65%65%
    Shear Modulus78.0 GPa11300 ksi
    Poisson’s Ratio0.27-0.300.27-0.30
    Elastic Modulus190-210 GPa27557-30457 ksi

    What is 01 Tool Steel?


    Similarly to A2 steel, O1 tool steel is also a cold-work steel. However, rather than hardening using air, it falls into the ‘O’ group of steels, which stands for oil-hardening


    O1 tool steel has a simple composition with high amounts of carbon and a small amount of Manganese. The addition of Mn is what makes this grade oil hardening; it is hardened using oil quenching in which the thermal shock of regular quenching is reduced, thereby minimising the risk of cracking. 


    With high machinability and relatively low temperatures required for hardening, O1 is a popular tool steel grade within the industry. It is a general-purpose steel suitable for a range of applications thanks to its high levels of wear resistance and toughness. Also, due to its simple and incredibly fine chemical structure, it can be easily honed to get the sharpest possible edge.


    Chemical Composition of O1 Tool Steel


    ElementContent (%)
    C0.95
    Mn1.20
    Si0.20
    Cr0.60
    Ni0.30
    W0.60
    V0.10
    S0.03

    Mechanical Properties of O1 Tool Steel


    Mechanical PropertiesMetricImperial
    Hardness, Brinell (soft annealed)190190
    Hardness, Rockwell C (tempering temp 149-649°C)34.0-64.034.0-64.0
    Elastic modulus (hardened to 62 HRC)193 GPa28000 ksi
    Elastic modulus (at 399°C, hardened to 62 HRC )172 GPa25000 ksi
    Elastic modulus (at 191°C, hardened to 62 HRC)186 GPa27000 ksi
    Compressive yield strength (0.2%, hardened to 50 HRC)1350 MPa196000 psi
    Compressive yield strength (0.2%, hardened to 55 HRC)1800 MPa261000 psi
    Compressive yield strength (0.2%, hardened to 60 HRC)2150 MPa312000 psi
    Compressive yield strength (0.2%, hardened to 62 HRC)2200 MPa319000 psi

    Applications of A2 Tool Steel

    With great qualities all-round, A2 tool steel is a popular steel grade for a range of applications. However, A2 is primarily used in situations where good wear resistance and high levels of toughness are required. 


    The most typical applications of A2 tool steel include:

    • Hammers
    • Lamination Tools
    • Lathe Centre Knives
    • Precision Tools
    • Machine Knives
    • Gauges
    • Shear Blades
    • Blanking Tools
    • Dies
      • Punch Dies
      • Trim Dies
      • Forming Dies
      • Stamping Dies
      • Thread Roller Dies

    As well as these, A2 steel is a popular steel grade in the knife-making community. Despite it requiring a lot of time and effort to sharpen, once sharp, you are left with a durable edge that lasts for a very long time – reducing the need for maintenance and filing.


    If you think A2 steel could be useful in your next project, contact us by calling 0114 233 5291 to find out more about our range and make the most of our extensive product knowledge.


    Applications of O1 Tool Steel


    Like A2 steel, O1 is also used for a range of applications due to its good qualities across the board. It is also affordable, making it popular amongst the DIY community and knifemakers.


    Here’s a list of the most typical applications of O1 tool steel:

    • Gauges
    • Jigs
    • Cutters
    • Stamps
    • Shims
    • Levers
    • Saws
    • Guides
    • Fixtures
    • Machine Parts
    • Punches
    • Dies
      • Blanking Dies
      • Forming Dies
      • Lamination Dies
      • Moulding Dies
      • Trim Dies
      • Screw Dies
      • Swaging Dies
      • Draw Dies

    A2 Vs O1: Choosing A Tool Steel


    Overall, as previously mentioned, there is no definitive answer to which tool steel grade is better as it ultimately depends upon the intended use. 


    When comparing A2 vs O1, it’s clear that they aren’t majorly different. Despite slight differences in toughness and edge retention, the rest of the characteristics like hardness, wear-resistance and machineability are all very similar. This is evident in their typical applications, as both steel grades are used for many of the same purposes!


    When it comes to picking one grade or the other, it’s best to prioritise the qualities you require for the intended purpose. For example, if you require a material that’s durable and won’t mark, with little to no maintenance required, the added Chromium makes A2 your best choice. 


    If you’re looking to make knives using the tool steel, it’s ultimately a personal preference. Many knifemakers prefer the A2 grade as it stays much sharper for longer thanks to its great edge retention. Whereas others struggle to get a sharp edge with their A2 in the first place and don’t mind the extra attention and sharpening that O1 steel requires. 


    Despite some differences in physical properties, both A2 and O1 tool steels are affordable grades that are suitable for many of the same applications. To ensure you purchase steel of the highest available quality it’s important to find a trustworthy supplier with knowledge and expertise.


    Here at Sheffield Gauge Plate, we stock both A2 and O1 tool steels in a range of sizes. We also stock a wide choice of other tool steel grades, if neither the A2 nor O1 possesses the qualities you require. 


    Our friendly team are on hand to answer your questions should you need extra help finding your ideal steel grade – contact us today for more information, or to place an order.