SK-4 steel
SK-4 steel is a Japanese carbon tool steel characterized by high hardness, sharpness, and good machinability. It is mainly used in traditional Japanese knives and tools where precision and blade durability are required.
Properties of SK-4 steel
Composition: this is a high-carbon steel with a carbon content of around 0.95–1.05%. It does not contain any significant alloying elements, which classifies it as a non-alloy carbon steel.
Hardness: it achieves a hardness of around 60–65 HRC, depending on heat treatment.
Sharpness: it grinds very well and achieves extreme sharpness.
Cutting ability: excellent, ideal for precise cuts and fine work.
Corrosion resistance: low – due to its high carbon content and absence of chromium, it is susceptible to corrosion and therefore requires regular maintenance and lubrication.
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Applications
Japanese kitchen knives (e.g., santoku, gyuto, nakiri)
Wood carving tools
Handmade knives and traditional tools
Manufacture of saws, chisels, and craft blades.
Advantages
Excellent sharpness and long edge retention
Easy to sharpen
More affordable than some high-alloy steels
Disadvantages
Requires regular maintenance (cleaning, drying, oiling)
Not suitable for use in aggressive or humid environments
Prone to corrosion and stains
SK-4 is a traditional Japanese carbon steel with excellent mechanical properties that will appeal especially to fans of classic knife-making materials. If you are looking for a steel that will provide a perfect edge but don't mind taking care of it, SK-4 is a great choice.
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Recommendations for use
Ideal for precision work – SK-4 is suitable for kitchen knives, carving tools, or workshop blades where sharpness and precision are valued.
Do not use on bones or frozen foods – the steel is hard but also more brittle, so there is a risk of chipping the blade.
Great for dry wood or fine work in the workshop – it excels in cutting tools such as chisels or saws.
Maintenance and care
Dry thoroughly after each use – even a small amount of moisture can cause corrosion.
Oil regularly – use mineral oil or blade oil, especially if the knife will not be used for some time.
Do not wash in the dishwasher – high temperatures, chemicals, and moisture will destroy the surface very quickly.
Store in a dry place – ideally in a case or on a magnetic strip away from damp environments.
Sharpening
Sharpen by hand on water stones – thanks to its high carbon content, it is easy to sharpen, so a 1000–3000 grit water stone is sufficient for regular maintenance, with a finer stone (6000+) for finishing.
Do not use electric sharpeners – high temperatures can damage the structure of the steel and "burn" the blade.
Who is SK-4 ideal for?
For enthusiasts of traditional Japanese knives who want to enjoy a sharp and precise knife with character.
For craftsmen and DIY enthusiasts who are looking for steel with excellent cutting performance and are willing to maintain it regularly.
For collectors and fans of handmade tools.