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SK-5 Steel Guide

SK-5 Steel Guide

Many famous movies depict swashbuckling heroes engaged in the finest exhibition of sword fighting as steel blades glisten in the evening sun. They take on a formidable enemy armed with just their sword.  What these men all had in common was knowing what makes a good blade, how to use the finest steel, and be effective with their weapon. Most of those weapons were designed using the toughest steel of the time. SK-5 steel is a modern steel that those men would love to have used.

Basic Info on Steel

Steel is manufactured from a combination of iron and carbon to which several other materials may be added. These extra components may include chromium, nickel, vanadium, tungsten, and manganese, These elements are added to perfect a type of steel with hardness, tensile strength and ductility (its ability to be shaped in different forms without coming apart or fracturing). Alloys are added according to the purpose of the steel once finished.

The higher the content of carbon, the harder and stronger the steel will become during the thermal process, but it will be less ductile (able to lose form without losing toughness). Chromium increases its hardness while nickel and manganese give it tensile strength and makes the iron-carbon solution of steel more stable. Vanadium also increases hardness and helps its ductility.

For the perfection of steel, the iron/carbon/alloy solution undergoes different types of heating or thermal processes to produce the final object. The solution is tempered through these processes to remove any defects or stresses in the material. This produces a high-quality product with the ductility, hardness and tensile strength desired in the steel.

(Read our review of balisongs).

How Steel is Rated

Steel is designated a numerical value to indicate its hardness according to the Rockwell C scale, otherwise known as HRC. The harder the steel the better its ability to hold an edge, but the more brittle and difficult to sharpen. The quality of the steel is largely dependent on the materials that go into its makeup and the forging process how well it is tempered.

How SK-5 Steel Compares

It is named after a Japanese scale but is similar in properties to the American 1080 steel, which is made up of approximately 0.80% carbon and up to 0.90% manganese. On the HRC scale, it ranks at approximately 65, which makes it a very hard steel. Its alloy increases its strength and abrasion resistance. It is a good, tough blade with a great edge-holding ability.

On this scale of commonly used knife-making steels, the SK-5 ranks way up there with ZDP-189 at the top of our hardness scale at HRC 65. A very hard, but potentially brittle steel that is a bit harder to sharpen, but sure holds its sharp edge for a very long time compared to virtually any other knife steel.



Uses for SK-5 Steel

Steel may be described as high or medium SK-5 steel. This has to do with its chemical makeup and the forging process. A high carbon steel is approximately 1080 which is a harder, stronger steel while a medium would have a carbon content of approximately 1050 or lower. Usually, the purpose of the steel determines its make up. The harder stronger SK-5 steel may be used in making tactile or hunting knives, while the medium steel is flexible and bends without breaking which is desirable in creating swords used in fencing. SK-5 is rarely used in machetes.

There are several factors that can affect the finished product of steel including environmental conditions, stresses and flaws in the chemicals in the solution, and the forging system. Manufacturers of steel are cognizant of this and usually, the greatest care is taken to ensure, that the steel produced is of the finest quality and will pass the scrutiny of the HRC.

Best Knife Made with Sk-5

The Columbia River Knife and Tool company’s Siwi, is a compact tactical fixed blade in a league all its own. This mission-ready knife has a durable SK-5 steel blade with a rust and corrosion resistant black powder coat.  It comes standard with G-10 scales which are textured.  A generous choil and subtle jimping on the spine offer better blade control and a solid grip. The Siwi is an exceptional knife that’s truly built to last several lifetimes!

crkt siwi fixed blade knife


SK5 steel is made for tools and weapons where their edge and high performance can be counted on for major operations and precision usages. See the best folding knife ever. They are highly tempered, forged in the highest furnace to reduce its flaws and produce products guaranteed to perform and do the task well for which they were created.


  1. Neither 1080 Steel Nor SK-5 Steel gets up to 65HRC Hardness!
    Who Writes this stuff?
    Don’t trust the internet!
    They lie.

  2. Daniel Boone predated Jim Bowie & the Bowie knife by a couple of decades. Thanks for the info on SK5 steel tho’, it was helpful!

  3. The Rockwell Hardness is not a rating, it is a mechanical property that can be measured with good precision. You said it was Rc 65 but is that in the as-quenched condition or the as-tempered condition? If that is as-quenched, you are being deceptive since the blade is not sold in the as-quenched condition. The as-tempered hardness would be about 5-10 points lower than as-quenched.

  4. Thanks, Peter. Your site looks nice.

    Don’t want to quibble, though I guess I am… The knife hardness chart is quite misleading. I suspect what you’re trying to get across is the upper limit of hardness ratings for each steel, or the average, or… ?

    Knife steel can be purchased pre-tempered (which case you get what you get from the casting or rolling mill) but most serious knife companies will temper their own, or contract for bulk stock tempering either from the mill or from a specialty shop. Point is, hardness is a quality imparted to metal by a process under the control of the knife maker, and while hardness range (not a bald number) varies by metal, knife makers can & should vary the hardness according to the desired properties of the knife. As determined to suit a given use profile.

    So D2 can be hardened all the way to 65 rc (you show 64 in your chart), but you pay a lot for D2 over 63rc. Knives of Alaska sells a 6″ Bush Camp Knife at 58-60 rc for under $100; Benchmade punches it up to 60-62 rc for their 4.2″ Adamas but the cost goes up, to $170 (and that’s bare metal, without bolsters). Most D2 knives are in fact sold at RC 57-59 or 60-61, a compromise between maximizing edge holding while keeping some hand sharpening ability (& I suspect reducing finishing costs). All listed costs per KnifeCenter, BTW, which is well below “retail MRP”, & which few stores charge. I couldn’t find a D2 blade at KnifeCenter listed over 62 rc, though I’m sure they must exist.

    Similarly, you comment that SK-5 (not actually on the chart) ranks with ZDP-189 at a hardness of 65 rc. Yes, ZDP-189 is sold incredibly hard – though most knife makers appear to back off a bit from 65 in the interest of enabling users to actually sharpen the product themselves – but I can’t find anyone selling a knife of SK-5 at 65 rc.

    Zknives.com identifies SK5 as “JIS standard name of AISI W108 steel. New JIS name is SK85. Water hardening tool steel, used in knives, spring, other cutting instruments and tools.” W108 is “Water hardening tool steel, comes in four grades, Special (Grade 1), Extra (Grade 2), Standard (Grade 3), Commercial (Grade 4).” Used for making files. Holds an edge – hardened in the 60’s, but W2 does it better with addition of Vanadium.

    The blade example you profiled – the CRKT Siwi with an SK5 blade – is apparently hardened by CRKT to 54-56 rc. Barely acceptable for bushcraft; certainly serviceable in the field. Nowhere near peak hardness for SK5, as you have indicated (hold that thought).

    If this metal can be hardened acceptably without fear of chipping well into the 60 range, it’s hard to see why CRKT is selling it at 54-55 (a huge drop a user absolutely would notice). Especially odd as the blade in question, with only 3″ edge, is 3/16″ thick – it’s a brick. SK-5 is fairly tough for tool steel, not particularly prone to breaking even when misused, and at 54-55 rc this is a soft blade, not brittle. At 3″ there won’t be fear it’ll chip with batonning: you aren’t going to baton anything that small and damage any knife (I want 5-7″ for a batonning blade, esp. for hardwoods). And you aren’t going to be striking harder blades in a knife fight with a 3″ stubbie (what the hell is it with sales of ‘tactical’ blades? who actually knife-fights in real life?). So what’s going on here is likely price control.

    This is how you keep the price low. KnifeCenter sells the Siwi currently for $64 US. W108 comes in 4 quality/price levels; I don’t know about SK-5. I presume CRKT is buying lowest available cost SK-5 slabs & not hardening, or not hardening much, which keeps finishing costs low. Bottom line on the knife: OK price for a nicely constructed short knife that’s built like a tank (5.6 oz.), too thick for fine work, will need sharpening frequently (but it can be). Won’t hold an edge like it could if tempered harder, but will hold it longer than soft steel or stainless at this hardness (it is tool steel, after all). Choil & jimping keep your fingers safe; coating on blade minimizes rust; G10 scales are nicely shaped, if they fit your hand. Worth the money if you don’t mind the drawbacks & don’t mind carrying a massive short soft slab of steel on your hip. D2 at this price range might give you more knife options; would definitely be harder (58-60 rc). Try bushcrafting oak or maple & you’d definitely notice the difference.

    But suggesting it’s hardness is necessarily anywhere near the same ballpark as ZDP-189 – at the same money – is unintentionally misleading. Same blade in ZDP-189 would hold an edge forever and take an eternity to hand sharpen with specialized tools, and would cost at least $200. ZDP-189 is always hard, but you pay for it.

    My point isn’t that SK-5 is crap, or can’t be bought harder. KnifeCenter claims Cold Steel’s 7″ Recon Tanto is SK-5, hardened to 64-65 rc. I’ve processed firewood for hours with that knife; it batons like a dream (length helps), and is still razor-sharp. At $42, it’s a steal of a deal!

    So if you want to point to a good example of SK-5 as a really hard knife blade, you might change the one you’ve profiled from the CRKT to Cold Steel’s Recon. Longer blade yet cheaper and much, much harder.

    Can I suggest you ditch the steel type hardness chart? Pretty picture, I know, but it doesn’t say anything – and what it does suggest is misleading as provided. And I’d suggest edit your text to better explain that hardness is an engineered attribute provided by the knife maker within hardness ranges that vary – perhaps a lot – by blade steel. That would be helpful, as many knife manufacturers don’t identify hardness.

    Hardness, toughness, strength and wear-resistance are the four properties that knife makers select among for optimal usage in a given blade. You can’t maximize all four: something has to give, so its a compromise, to achieve the best results for a particular use case. It is helpful for a user to know what the manufacturer is choosing as attributes, or you can’t estimate how a knife will perform for you. You likely know this, but it isn’t information that comes across in your web site.

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