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Unraveling the Differences Between SK85 and SK5 Carbon Tool Steels

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SK85 SK5 JIS carbon tool steel


In the world of precision engineering and tool manufacturing, the choice of material can make all the difference. Two such materials that have stood the test of time are SK85 and SK5, both carbon tool steels under the JIS G 4401-2006 standard. While they may seem similar at first glance, they possess distinct characteristics that make them suitable for different applications. In this blog post, we delve into the nuances of SK85 and SK5, exploring their chemical compositions, heat treatment properties, and the specific uses that set them apart.

SK85 and SK5: A Comparative Analysis

SK85 and SK5 are both high-carbon tool steels known for their hardness and wear resistance. However, they cater to different needs in the manufacturing industry.

SK85: The Premium Choice

SK85 is considered a superior grade of carbon tool steel, with a carbon content ranging from 0.80% to 0.90%. After quenching, it can achieve a hardness of 50-60HRC, making it an ideal material for tools that require high hardness and excellent wear resistance, such as cold work dies and cutting tools.

SK85 carbon steel

SK85 carbon steel

SK5: The Versatile Option

SK5, with a slightly lower carbon content in the same range of 0.80%-0.90%, quenches to a hardness of approximately 57HRC. It is well-suited for tools that demand both toughness and wear resistance, such as simple molds and punches, and woodworking tools like milling cutters.

sk5 steel coil
sk5 steel coil

Application-Specific Selection

The choice between SK85 and SK5 depends on the performance requirements of the tool. For precision stamping dies, SK85 might be the preferred choice due to its higher hardness and wear resistance. Conversely, for tools that require greater toughness, such as woodworking tools, SK5 could be the better option.

flat metal part

band saw blade

Heat Treatment: A Crucial Difference

While both SK85 and SK5 are high-carbon tool steels, their heat treatment hardness ranges differ. SK5 has a specified heat treatment range, but SK85’s exact range is not explicitly provided. However, based on their similar chemical compositions, it is reasonable to infer that SK85’s heat treatment hardness may be comparable to SK5’s.

Why SK85’s Carbon Content is Slightly Higher

Although both SK85 and SK5 have a carbon content of 0.80-0.90%, SK85 is considered an upgraded version of SK5. This suggests that while there may not be a significant difference in carbon content, SK85 likely boasts improvements in other areas such as heat treatment and hardenability, resulting in superior overall performance.


Both SK85 and SK5 are exceptional carbon tool steels, offering good machinability and heat treatment responsiveness. The decision to use one over the other ultimately depends on the intended use and performance requirements of the tool.

Final Thoughts: In the precision-driven world of tool manufacturing, understanding the subtle differences between materials like SK85 and SK5 can lead to the creation of tools that are not only more efficient but also longer-lasting. Whether you’re reaching for the premium performance of SK85 or the versatile reliability of SK5, knowing their unique properties will guide you in making the right choice for your specific needs.

Note: This blog post aims to provide a comprehensive comparison between SK85 and SK5 carbon tool steels, highlighting their differences and applications. It is intended for readers interested in material science, engineering, and manufacturing.

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