Carbon Steel Performance

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brownshoe

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I have a small (3" upswept persion type) blade. It is convex ground, mirror polish. It was cut from a sawmill blade by an Amishman who sells bakery products in my city market. The construction is a little rough, you can see file marks. I've had it for years, only $25. It sat and slightly rusted in a drawer. Saw some usage camping.

Reading about convex edges and the superiority of carbon vs. stainless in this forum, I decided to give the blade the acid test. No longer a drawer queen, I turned it over to the family in the kitchen. The only protection I gave it was a coat of olive oil about every 4 weeks. It's been used in the kitchen for 4 months. It has developed a "patina" but never really rusted, although the patina is really dark in some spots. It has bounced around and hit plates, the sink, etc., but the edge is unchipped and in good shape. It was stored on a magenetic knife holder, not in a sheath. I've not sharpened it, although it may have been steeled a couple of times I'm sure its never been sharpened, because my family doesn't sharpen, I do. It still cuts tomatoes like a serrated blade. It splits chicken breasts like a chisel.

All and all, great performance. Holds an edge much better than my stainless kitchen knives and also better than a carbon steel paring knife. It has become a favorite among some family members.

Anyone can guess my blade steel? It's at least a 50 year old saw blade.

Anyone else get such great performance out of a carbon steel sleeper?
 
These blades are usually L6 or similar, in the saws they are usually left fairly soft to avoid breaking as they turn at high speeds and can crack into knots. However the steel can be hardened up to 65 HRC so the performance you see in a knife is radically dependent on the makers heat treating, some just leave them with the saw hardness.

As for performance, I would not be so quick to say it is high. A few years back I intended to add a kitchen use section to the edge retention information in the reviews, however the low end benchmark blade (cheapest stainless paring knife I could find) never significantly dulled through repeated weeks of careful cutting on various foods.

In general kithchen use is so light that edge retention tends to be dominated by accidental impacts or misuse[*]. I have even made test blades out of mild steel and they stay sharp for extended periods of time cutting foods, and yes, even working on small chickens. Poultry bones are in general really soft, as an extreme, I recently used a custom with a ~5 degree edge (yes a flat five degrees per side ) to take apart a 18 lbs turkey, the edge was damaged, but very slightly, the maximum chip was < 0.5 mm in depth.

[*] some exception to this are working on a lot of shell fish, cutting fish with a lot of bones, or with very tough skin like shark [really abrasive], or preparing a lot of fresh and unwashed vegetables so the knife contacts the dirt frequently.

-Cliff
 
I agree with Cliff that it may be L-6. I share your opinion regarding carbon steels. I have a custom forged L-6 that is awesome in cutting and is very easily sharpened & maintained with a steel.
 
Cliff, I agree that food preparation is often not hard on a knife; however, the same is not true for my family. They will dull virtually any knife in less than a month. So using my family as the "test bed" the performance of this blade is significantly better than other knives in my kitchen. For example, knives, including this one, often sit soaking in a pot of dishwater to remove previously dried on food. That's one of the reasons I was suprised at the lack of rust; the polished finish probably helps. If the blade can be hardened to 65, maybe its cutting performance is a combination of this hardness plus the grind. The knife has a thick spine (1/4") going to a edge in about 1" at its widest point. It does have a convex grind with just the tiniest secondary bevel, so thin you can barely see it.

As to construction, the knife shape was cut out of the saw blade, and shaped by stock removal. That's why it has a thick spine. I know nothing about it's heat treat.
 
L6 and the like tend to rust really easily. For example if you use one to cut up an apple, you will see visible orange and blade rust before you finish eating the apple. It is has even a decent amount of corrosion resistance I would expect it may be a different steel but there are not a lot of saw blades that are high alloy. However you could have a Stellite alloy, they have been and still are used in saw blades. You could check it on a file. If it is really hard the file will skate over it like glass.

-Cliff
 
It could be L6, or it could be just about any medium to high carbon plain carbon or low alloy steel. Steels with .7-.8% carbon (such as L6, 1070 and 8670 etc.) seem to be most common for wood saw blades. Hardness is typically kept around 40HRC for toughness.


If Stellite is used for wood saws, it is for the tips to increase wear resistance, not for the whole blade. Besides, if the blade made of Stellite it would be rust proof and would not take a patina.


You could have someone who knows what they are doing to spark test your knife if you want to get a better idea of what steel it is.





- Frank
 
There are blades made out of cobalt alloys, the whole blade. There was some performance comparisons vs various steels in an ASM book, Tool Steels if I recall correctly. The main advantage was the lack of corrosion resistance. Though yes you would not get a patina with a Cobalt alloy. L6 and its similar alloys will take a patina very rapidly and will in fact rust (orange) very easily. If you are actually letting it sit around wet I can't see it just going black. It would pit and show rust.

-Cliff
 
The longer edge life in the comparison I read was attributed to the corrosion resistance of the particular Cobalt alloy, the corrosion rate of steels is highly excellerated as the temperature is raised (as are most chemical reactions). Cobalt alloys are used for a lot of tools, you can for example find Cobalt chisels, I have a small one.

-Cliff
 
I'm not arguing the content or natuer of the saw blade. Most are a high-carbon alloy, usually a steel that is tougher for use as a saw. For a knife blade, that can only mean good things.

I am unabashedly a carbon steel fan - period. I'd go as far as to say that carbon steel doesn't just cut longer and stay tougher, but it also cuts differently. And I can feel it, and I like that feel. One of the best features of carbon steels is that despite great edge holding and toughness, most are really quite easy to resharpen. Cliff Stamp would undoubtedly have a proper explanation for why that is. Most stainless steels designed for edge holding or toughness do so at the expense of becoming very difficult to sharpen. This is IMHO only. Jason.
 
I think its neat that a $25 blade, from an amatuer maker, constructed of scrap metal, scrap wood, and copper wire, can give such great performance. Makes you wonder, if old scrap saw blade steel can give such good performance, is there any real need for the wonder steels?

It also makes you feel that if a $25 hand made blade can pass full muster, for a using knife, I must be a fool when I pay more for sometimes less performance, but certainly a more sexy blade. Why have a good looking high dollar woman, when the plainer one is cheaper and gives as good or better performance and turns out to be more popular?
 
Jason, you are right on the mark and I couldn't agree with you more!!
I love carbon steels for the reasons you mention!
 
While L6 is great steel for knives it sure is a pain in the ass to work.
I spent 4 hours cutting out a blank out of a circular saw blade.
(Im a glutton for punishment).
Really felt like an idiot after I got some O1 stock from a supplier.
It was easier to cut through quarter inch O1 than the rather thin saw blade.
I was even considering using the L6 blade at its current hardness for a working knife but I was quessing it was a lot harder than 40 hrc.
 
MC Chan, I think your L-6 steel was in some hardened state. The O-1 stock you got would have been annealed. In annealed state L-6 is no more difficult to cut than O-1.

But yes, I personally think L-6 has a few quirks that might explain why it is not as popular as 5160, 1084 for forging. It tends to air harden a bit and like O-1 and 52100, doesn't move under the hammer so easily. Jason.
 
Out of the 70 or so kitchen knives that I own, from cleavers to specialty garde manger knives, I'd have to say that I like my "high carbon" non-stainless knives the best. They do have a different feel to them and are easier to steel and sharpen. I don't mind the patina and have never found rust a problem. My favorites are two old Chicago Cutlery Chef's knives, 8" and 10".
 
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