Some steels get sharper than others?

[Quy4n8]

I have read in a number of posts that steel A actually gets sharper than steel B. If one assumes good steel with a good heat treat and equal geometries, is this true? If so, why? I understand grain size and so forth, but is this not smaller than the edge itself? If this is true, what steels would be at the high end and does this make much difference in actual use, or is this very fine edge just rolled or worn away after the first few cuts. Any thoughts would be most appreciated.

Richard

 

[Cliff Stamp]

I have read in a number of posts that steel A actually gets sharper than steel B.

Jeff Clark and I disagreed about this many years ago where he talked about being able to get certain steels sharper. We were in opposition simply as he was *MUCH* better at sharpening, still is, but I am not as incompetent in comparison.

If your standards for sharpness is that a blade can slice a piece of paper then pretty much any steel will do and you will never see any difference from one to another. However some people have much higher standards and as you demand more you see differences.

Here is one of, if not the highest standard I have seen to date :

Take a piece of newsprint, fold it so that a 1/4" - 3/8" piece sticks up perpendicular to the sheet, press your knife into it, no draw, and not at an angle.
[*]

When you start think of performance by these standards as meaning sharp you start to see differences where others will not. Note specifically that there are people for whom this isn't exceptional, not a great sharpening job, just a competent one.

There are several reasons why some steels won't get sharp. First is hardness, when a steel is really soft it can be difficult to get a crisp edge, burr formation is difficult to minimise, and thus even if you could get it optimally sharp, you never do in practice.

The other is grain size, this comes out especially in very low angles, the finer you bring your edges the more of an effect this will induce. If you go really low, 3-5 degrees, some steels actually break apart under the hone and thus there is no use in going beyond a certain grain abrasive wise.

-Cliff

[*] Alvin Johnson

 

[GoodGuy]

it's been my experience that the uniformity of the steel's grain (size and orientation) on and along the edge can impact the degree to which one can sharpen that edge. to me, it's a bit analogous to the differences between a ripping and a cross-cut saw (or, perhaps, the difference between a steel alloy edge and a glass edge). the structure of the steel itself will limit the theoretical sharpness of any edge regardless of the edge geometery. at least that's been my experience. edges with relatively finer grain structures and a unidirectional grain orientation can be made sharper than coarser grains structures having a "scattered" grain orientation.

practically speaking, and using the sharpening tools readily available, it seems to me that high carbon tool steels usually produce edges with superior sharpness.

with that said, the sharpest tool i have and occasionally use is a medium sized obsidian flake wrapped in a leather formed handle of sorts.

 

[STR]

I agree with Cliff for the most part and could add that sharpness comes in several ways. First there is the real good slicing sharpness where the edge is a bit more aggressive. This type of edge usually will not push cut very well so if sharpness is determined by say push cuts when carving it is probably not going to be adequate even though it would slice tomatos or other veges all day long.

Second is the highly polished edge that is primarily a push cutter but would actually be hard to start into a tomato by a slicing action even though it is a finely honed highly polished edge that takes hairs off above the arm.

Third is the happy medium between these two where you can get some of the best of both worlds.

And of course the angle, edge geometry, blade thickness, type of grind and the end user all account for what is termed sharp. In my experience you can pick up any standard brand new Spyderco knife and find a good place to get an idea of what sharp is. I basically judge sharp or dull from using a good Spydie as a standard and the bar moves up or down accordingly from there.

As for steels. Some have given me fits more than others. ATS34 and 154CM are my least favorite steels and yet they keep coming into my pocket because I find many knives that I love other than the blade steel. I've been guilty of saying that these two take a crappy edge and hold onto it for a long time. I don't know why these two in particular seem harder for me to sharpen but they do and repeatedly. My latest fiasco is my BM 420 Resistor. Just a crappy but useable edge is all I can get on it. Go figure.

 

[db]

For me yes, and I don't know why. Here is a few that seem to get really sharp for me, stainless AUS 8 and VG 10, and nonstainless A2, and 52100.

 

[Lavan]

I have a MCusta in VG 10 that is sharper than ANY knife I have or have EVER had.
It will not pass that "press into newsprint" test (I just tried) but it would sure pass any OTHER test of sharp. (on the newsprint, it WILL cut with the SLIGHTEST draw or push)

SCARY sharp lil thing.

 

[STR]

I think VG10 is perhaps the best steel out there for the general public. Even a lay person can make it sharp so in that respect it seems to be an easier steel to sharpen from numerous reports both here and on other forums.

I find VG10 to be a very satifying steel to sharpen because it takes a great biting edge and seems to me to hold onto it quite well also. Some of my Spyderco knives in VG10 were terrifyingly sharp out of the box. I don't think it is up there in wear resistance or edge holding with D2 or S30V but by all accounts it seems to be a bit easier to get a satisfying edge on for the masses based on the reports of 'easy sharpening' so the drawbacks are outweighed there IMO.

 

[Joe Talmadge]

I too always saw differences between steels. I always nodded my head when Cliff would explain to me why it was impossible for me to see these differences , but nevertheless, I saw that I could consistently get some steels sharper than others. The most obvious case was when AG Russell sent me three Deerhunters to test, all with very close edge profiles: ATS-34, a mystery steel that he still hasn't disclosed to me, and 8A. I re-sharpened the three on the same system, to the same angle, using the same techniques, and (as usual versus ATS-34) the 8A knife was the sharpest. That helped convince me I wasn't just imagining things, or seeing some weird statistical thing where all my VG-10 and 8A blades were particularly thin and well heat-treated, and my other blades were not.

 

[Habeas Corpus]

I find VG10 to be a very satifying steel to sharpen because it takes a great biting edge and seems to me to hold onto it quite well also.

I totally agree. A lot easier to sharpen than S30V in my experience, and it does seem me to get sharper when comparing knives with very similar edge geometry. Other stainless steels I quite like in that respect are ATS-55 (surely one of the most underrated steels ever) and especially Sandvik 12C27. The Sandvik doesn't hold an edge like some of the other steels, but it gets pretty sharp quite easily.

On the other hand, there are quite a few "old-fashioned" carbon steels that beat the crap out of most of the stainless steels. Their only real disadvantage is, well, that they're not stainless. 1095 with decent heat treatment for instance takes an incredible edge.

Hans

 

[Quy4n8]

Thank you gentlemen, that does clear some things up. It appears that, in general, plain carbon steels will be able to attain sharper edges than stainless steels (with the exception possibly of VG10) due to their finer grain structure and some would argue this is true of knives in general and some would say only on blades with very narrow included angles. First, the steel has to be hard enough to actually take a good edge. Since it seems to be a standard, say we call Spyderco’s edges our baseline for sharp. Well, how hard is that; 52 Rc, 55 Rc, 58 Rc? I know that different steels will have different levels of hardness when optimally heat treated, but is there a point which most steels will get “sharp” if heat treated to that point? Or is this being to general, i.e. I could get a “sharp” edge on A2 at 56 Rc, but CPM-S30V would have to be 59 Rc to attain the same level of sharpness? Throughout all of this I am assuming equal geometries.

 

[Satrang]

The differences with the various steels are due to property variations. Geometry aside, an edge will try to mimic the abrasive used to form it. This is where the microscopic "teeth" come into play. Some materials will lose these teeth due to low fracture toughness or will lose them during use. When this happens the geometry changes and you have un-equal cutting conditions. Now add in carbide content, hardness , etc. and you have one complicated situation. It is easy to see why there is no perfect solution. No one materials exists that can maximize all the properties needed for all types of cutting. Thus the debate of steels will continue to infinity. Kind of like the BCS in football.

 

[Danbo]

I think that few steels get as scary sharp as W2.

 

[cerulean]

MCusta makes some truly vorpal knives. Their VG-10 blades are definitely sharp enough to qualify as scary in my book. I can imagine one of those suckers passing through a finger without its owner even noticing. In my experience, they’re actually a bit sharper than Spyderco’s VG-10 bladed folders.

Earlier today, I sharpened a couple of knives: a Roselli puukko with a simple carbon steel blade and a Cold Steel Voyager with an AUS-8 blade. The puukko was a piece of cake, but I had a hard time with the Voyager. I kept creating a large burr that I just couldn’t remove cleanly and it never got as sharp as I wanted. Its steel may have been a little bit softer than some other 8A blades.

The VG-10 blades that I’ve sharpened before have never been problematic. It’s easy to create a small, well-formed burr that doesn’t flop around or break off in shards when you try to remove it. I don’t know if that steel is inherently able to produce a sharper edge than anything else, but the MCusta knives I have really show what it’s capable of.

 

[sodak]

This is a great question! I can get all of my knives equally sharp if I use my edgepro apex. That's a no brainer. I can sharpen some more than others by hand, and here AUS 8A and VG 10 are among the best. But they're stainless, so those large chromium carbides should be getting in the way. But they don't seem to be. I can also get D2, which is notorious for large carbides, just as sharp as 5160 or 1095 on the edgepro. Go figure.

Either I'm not good enough at measuring sharpness, or else there is no difference. Some are easier to get there than others, but all can "get there". At least at my level of perception. Perhaps if you could measure sharpness more accurately, there would be a difference.

I also have both high carbon and stainless straight razors. They both shave the same, and hurt the same when they cut!

 

[Cliff Stamp]

I can get all of my knives equally sharp if I use my edgepro apex.

What do you use as your standard, what does a knife have to do for you to call it sharp?

It appears that, in general, plain carbon steels will be able to attain sharper edges than stainless steels ...

Some alloy steels work very well, 52100 for example has a very fine grain, and should be better than 1095, and M2 at a high hardness gets very sharp, the finishing steels should pretty much be the ultimate in this regard, last I checked Alvin was still looking for some to grind some knives.

...I could get a “sharp” edge on A2 at 56 Rc, but CPM-S30V would have to be 59 Rc to attain the same level of sharpness?

That is an interesting question, some steels can't get to the grain size of others. I don't think it is possible for example to heat treat D2 so that even with its finest grain it would match 52100 even if you left the 52100 fairly coarse and soft at around 58 HRC (compared to its maximum limit).

Due to the massive changes in alloy influence, the answer, even when possible would change significantly from one steel to another.

-Cliff

 

[sodak]

What do you use as your standard, what does a knife have to do for you to call it sharp?
-Cliff

I gotta get the hang of these quotes....

Excellent question!

I sharpen most of them to the 3000 grit tape and close to the same angle, around 15 deg total. I have an old CS Master Hunter in (the dreaded unknown) Carbon V that's been retired that I use for a reference. You would think the edge would corrode over time, but in my dry high altitude climate, it doesn't seem to happen. I can and do freshen it with the 3000 tape and a strop. This is my "control group", as my wife would say.

To be called sharp, I do a number of tests. I first check the edge manually with my index and middle finger, perpendicular to the blade. Mainly to check for a burr, but also to make sure that there is the same degree of "grabbiness" both ways. Then I go to newspaper, sometimes (even better), very, very thin newsprint such as a cheap Campmor catalog. I check both the push cutting and slicing ability against the Master Hunter. If it passes muster, then I shave a letter off of the newspaper without going all the way through. This requires a thin edge, but almost all of mine are thin. Passing all of these, then I try "tree top" shaving. Holding the knife about 1/4 of an inch or so above my elbow and/or forearm, I bring it up (push cutting) against the grain of my arm hair. Really sharp knives tend to cut a hair or two on every pass. My straight razors cut a dozen or two on every pass, but they are so delicate that they are useless except for shaving. If I start at the elbow, I run the blade up the outside of my bicep. If I start at the forearm (arm bent at 90 deg at the elbow), I follow the outer contour of the forearm from "pinky" side to "thumb" side if you know what I mean. I wish I were a medical professional to be more precise in my terminology.

Anyway, if a knive can equal my Master Hunter on the newsprint, I consider it sharp. If it can tree top my arm hair, then I consider it possessed and call an exorcist.

I realize that these are all subjective tests, and don't involve direct measuring. At least I have a known standard that I consider "sharp" (that means it scares me). If you would like to see this Master Hunter, I would be happy to send it to you so that you can judge it for yourself.

PS - Cliff, I'll be getting my dig camera back this next week, and will send you the rest of the pics that I promised.

 

[Cliff Stamp]

I first check the edge ...

That is pretty impressive, I don't think there are many people who would have a problem with a blade which could do the above. I look forward to the shots.

-Cliff

 

[Shmackey]

Here is one of, if not the highest standard I have seen to date :

Take a piece of newsprint, fold it so that a 1/4" - 3/8" piece sticks up perpendicular to the sheet, press your knife into it, no draw, and not at an angle.
[*]

I'm having a hard time picturing this. Is the fold in the middle, and not a crisp fold, so that you're making a sort of Greek letter omega?

 

[Cliff Stamp]

Just fold the edge of the sheet up thus the paper has an L shape. It is pretty difficult to cut because the paper isn't very rigid and bends easily. If is easy in comparison if you hold on to the paper while cutting which is how most test push cutting newsprint.

-Cliff

 

[Shmackey]

Makes sense. Thanks, Cliff.