52100

Composition: 52100 is a classic ball-bearing steel that has become a favorite in knife making. Approximately 1.0% Carbon, 1.3–1.6% Chromium, 0.25% Manganese, 0.30% Silicon, with maybe 0.025% each P and S. No vanadium or moly in standard 52100 (it’s a simple alloy: high carbon with enough chromium to significantly increase hardenability and form some chromium carbides, but not enough to be stainless). It’s also known by names like 100Cr6, SUJ2 (Japan), 1.3505, etc.. The chromium content (about 1.5%) is the defining element beyond carbon – it’s what differentiates it from simple carbon steel and gives it that bearing quality of fine, hard carbides dispersed in a tough matrix. Hardness: 52100 can reach about 62–64 HRC at its upper end with a proper quench. Commonly, knives are tempered to ~60–62 HRC for a good blend of strength and toughness (bearing balls themselves are often around 62 HRC). Many custom makers like to aim around 61 HRC for heavy-use knives or as high as 63 for slicing knives, and 52100 responds well to advanced heat treats (some use triple quench or low-temp cycles to refine structure). It has a fine grain and can get very hard without being brittle if done correctly. The result: a 52100 blade is typically harder than most production stainless knives, which was one reason it became known for superior edges in the custom world. Phil Wilson (custom maker) famously pushed 52100 to high hardness and touted its performance. Overall, expect around 60 HRC in many factory knives (e.g., Benchmade’s 52100 runs or Marble’s), and up to 63 HRC in customs or specialized blades – at those hardness levels, it performs excellently and still isn’t overly chippy. Edge Retention: For a low-alloy steel, 52100’s edge retention is considered very good – better than O1 and on par or better than 1095/XC100. It’s often said to “hold an edge a little better than O1, and also tougher”. The chromium carbides (Fe/Cr_3C carbides) formed in 52100 provide increased wear resistance over plain carbon steels, and combined with high hardness, that yields a longer-lasting edge. Many comparisons note that 52100 can approach the edge retention of D2 in some tasks while being much tougher (D2 has more carbides but 52100 has finer ones and higher toughness). In CATRA testing, 52100 often does surprisingly well, outpacing simpler alloys. Users find that it keeps a fine edge through a lot of work: skinning multiple animals, extended kitchen prep, woodworking tasks – 52100 stays slicing efficiently. It was historically used in razor blades (early Gillette experiments included SUJ2 steel) due to its ability to hold a sharp edge. It’s not a “super steel” by modern powder standards, but it’s likely the highest edge retention among the traditional simple steels (aside from maybe.Aogami Super, etc.). Another aspect is it has been observed to maintain a very keen edge (it can keep that sticky sharp feeling rather than quickly dropping to just a working edge). This was noted in Larrin Thomas’s research: after accounting for hardness, 52100’s chromium-rich carbides gave it a slight bump in wear resistance compared to plain high carbon steel. In summary, relative to common 1095/XC100 or O1, you’ll sharpen 52100 less often for the same work. Toughness: 52100 is known for excellent toughness relative to its hardness. As a bearing steel, it had to withstand repeated stress and impacts, so it’s formulated to be clean (low P, S) and fine-grained. Knife makers often praise its ability to take abuse: it’s tougher than D2 or other high wear steels by a significant margin. Charpy tests (from what data is available) show 52100’s toughness is quite high among knife steels in the ~60 HRC range. For instance, it’s tougher than O1 (which has small Cr and W, making it a bit less tough). Some even compare it to simpler spring steels in feel – it doesn’t chip easily, rather, it will tend to roll or bend slightly under extreme stress. This is why it’s been used in applications like thin kitchen knives (less chipping) and even in some swords. For outdoor knives, 52100 became popular because you could have a high-hardness edge that didn’t chip out in cold weather or heavy use (one reason many ABS Master Smiths used 52100 in performance test knives in the past). Ed Fowler famously championed 52100 for hunting knives, focusing on multiple quench cycles to get a super-tough, fine carbide structure – his knives would flex and bend without breaking. While not all 52100 knives are like that (heat treatment can vary), the steel’s inherent toughness is a big asset. In practical terms, a 52100 blade can often be ground thinner than a brittle stainless, giving better cutting performance without fear of chipping. Overall, it’s considered a tough steel for its hardness class, making it great for impact or twisting cuts. Corrosion Resistance: Low – it’s basically a high-carbon tool steel, not stainless. With ~1.5% Cr (and most of that tied in carbides), it will rust if not maintained. It is slightly more corrosion resistant than 1095/XC100 or O1, mostly due to the chromium content forming a bit of Cr_2O_3 passive layer, but this effect is minimal. People do note that 52100 might patina a bit differently (sometimes a slightly more mottled patina) and perhaps very slightly slower to rust than plain carbon, but practically it’s a carbon steel: it will form patina quickly and red rust if left wet or with acidic material. So all the usual carbon steel care applies – keep it dry, wipe it during use, oil if storing. In knives, it often develops a nice grey-blue patina with use which can protect it somewhat. But put a 52100 blade next to any true stainless and you’ll see rust on the 52100 first. The “stain resistance” of 52100 is sometimes said to be akin to SK-5 or other low-alloy steels – negligible difference. That being said, because it has less weird additives than some other tool steels, the patina can actually be quite attractive (a smooth, even dark patina if done intentionally with mustard/vinegar). In short: treat it like 1095/XC100 for care purposes. The chromium in it is for hardenability/wear, not for rust prevention (full stainless needs ~13% Cr in solution, and 52100 only has ~0.5% in solution). So if you want a “stainless 52100,” look to AEB-L (which was basically a development to mimic 52100’s properties in stainless form). Sharpening & Edge Behavior: 52100 has a reputation as a fantastically sharpening steel. Its grain structure is very fine (especially if properly heat-treated with good spheroidizing etc.). It doesn’t have massive vanadium carbides to contend with – only chromium carbides, which are not too difficult for standard aluminum-oxide stones. As a result, it sharpens relatively easily and takes a very keen edge. Cutlers often say 52100 can get “scary sharp” – similar to simple carbon steels like 1084, but perhaps even keener because it can be harder and still fine-grained. Murray Carter once remarked that 52100 blades sharpen up to edges nearly as keen as White steel. The burr formation is usually small and manageable. One may find it ever so slightly more wear-resistant to sharpen than a 1095/XC100 (the chromium carbides add a touch of abrasion resistance), but it’s still far easier than high-alloy stainless or PM steels. Polishing it to a mirror edge is quite feasible, and it holds that polish nicely. In terms of edge behavior, 52100 is beloved for its combination of edge stability and wear. It can support very acute angles without crumbling – you can sharpen at a low angle to get a really thin edge, and thanks to the toughness, it tends to roll rather than chip if overstressed. That makes field maintenance easy (you can often steel or strop a rolled edge back). The edge can also have a good aggressive slicing bite if left at medium grit – that’s the chromium carbides acting like tiny micro-teeth. Many who use 52100 kitchen knives find that at, say, a 3000-5000 grit finish, it push-cuts well but also has enough bite for tomatoes, etc., and it remains for a long time. When it does dull, it does so in a forgiving manner (gradual dulling vs catastrophic chipping). One interesting note: Larrin Thomas pointed out that 52100’s chromium carbides are a bit harder than pure iron carbides, so it can sustain abrasive cutting (like cardboard) better than a plain carbon steel, giving it that above-mentioned edge retention boost. This means if you cut a lot of rope or cardboard, 52100 will keep slicing longer before it goes completely dull. And when it finally does, a few swipes on a stone bring it right back to life. Many custom makers choose 52100 for high-performance blades because it has this excellent combination of sharpening response and edge endurance – often summarized as “takes a crazy edge and holds it surprisingly long.” Ideal Applications: 52100 is extremely versatile. It started in bearings but has been used for decades in knives of all types. It’s fantastic for kitchen knives – many Japanese carbon knives labeled “Gyuoto in carbon steel” historically might have been something like SK-3 or 52100 equivalent. Bob Kramer famously used 52100 in his carbon steel kitchen knives, leading to their near-mythic status for performance. It excels in thin kitchen blades due to sharpness and toughness. For hunting and outdoor knives, 52100 is top-notch: it holds an edge through skinning and can take a very fine edge for field dressing. Its toughness means you can baton wood reasonably (if geometry allows) without worrying as much as you would with something like D2. It’s also common in forged blades – ABS smiths often use 52100 for performance test knives, camp knives, and competition cutters where they need a blade that can both push-cut and withstand bending tests. Some makers have even used it in swords or large blades (Howard Clark made some bainite 52100 katanas historically) because of its toughness and ability to flex (though high carbon content can be tricky in very long blades). But primarily, think of 52100 for any knife where you want a superb cutting edge and are okay with non-stainless: chef’s knives, bushcraft knives, folding knives (there have been sprint run folders in 52100, like Spyderco did a Military and ParaMilitary in 52100 at ~62 HRC), and chisels/planer blades too. Notable Uses & Makers: Historically, Ed Fowler and Bill Moran popularized 52100 in the custom world for hunters, demonstrating its performance. Jerry Fisk and others also spoke highly of it. In kitchen knives, Bob Kramer’s custom carbon series was 52100, leading to great demand. Benchmade did some limited models in 52100 (e.g., a Messermeister kitchen collab, IIRC). Spyderco’s 52100 Military sprint was highly praised by users who noted how fine the edge was. Fallkniven occasionally references using a bearing steel in laminated blades (though usually that’s 52100’s cousin 19C27 for them). Essentially, many custom makers will still pick 52100 as a go-to carbon steel if they want ultimate edge quality – it’s often considered a step above 1095/XC100, O1, W2, etc., in overall balance. The steel has an almost legendary status due to people like Phil Wilson and Ed Fowler writing about its merits. The only caution is it requires a precise heat treat to unlock its best (proper spheroidizing, soak, etc.), but in competent hands it yields arguably one of the best knife steels around when you consider all factors (excluding the need for rust care). Many say, “If I could only have one steel for a using knife (ignoring rust), it’d be 52100,” because it’s that well-rounded.