Stainless Vs. Carbon Vs. Tool Steels

cm_bushman · May 23, 2013

I'm wondering what you guys think of the sharpening of stainless, carbon, and tool steels. Is there a difference in your experience, or is it simply the same method, different time-frames?

I always see members here talking "ease of sharpening". Most of the time, I take it as the length of time it takes to sharpen a certain steel, but sometimes you hear about certain steels like D2 that some proclaim just won't get sharp. You also hear how plain carbon steels are "easier" to sharpen than stainless steels. I have always wondered if there was any merit to this, though I'm sure there are differences due to grain structure, carbide volume, toughness, etc. I just don't know if they're large enough to make a real difference when sharpening. I'm sure there is a lot of preference in these statements as well, as everyone has a different level of sharpness they consider acceptable.

The reason I ask is twofold:

First of all, and what has me really wondering about this is I received my first knife in CPM-M4 a couple of weeks ago, and it is my first blade in a tool steel. Something I have noticed is that a quick strop on a bare scrap of leather made a sizable difference in the tangible sharpness of the edge, from barely cutting paper to shaving easily. The only other knives I currently have are all stainless (154CM, 440C, etc.), and I have never been able to see nearly the same difference from stropping them.

Secondly, I'm thinking of investing in a quality full-tang Scandi "bushcraft" style knife for my main camp knife, and O1 seems to be the preferred steel in this application for "ease of sharpening". I plan on taking a sharpening stone with me while I camp, so I'm wondering about the difference between O1 and something more wear resistant like M4, or something stainless like S30v. Will the difference just be time, or will O1 sharpen up more easily in some other respect than these steels? If the only difference is time, how much of a difference will there be?

dogstar · May 23, 2013

I'm one of those guys who has an easier time with carbon. My carbon knives get sharper with less effort. Perhaps I'm just a newb at sharpening or I don't have the right tools.

michaelm466 · May 23, 2013

In general, easiest to most difficult: Carbon > Tool > Stainless, however it is also dependent on carbides, and hardness as well. For instance S90V is harder to sharpen than S30V at the same hardness because S90V has more carbides, S30V at 57hrc will be easier to sharpen than S30V at 61 Hrc due to hardness, it can also go the other way, specifically with softer or poorly heat treated steels like junk knives will an an Hrc in the 40s due to the burr you can never really get rid of. O1 is easy to sharpen because it doesn't have a lot of extra carbide (though it does have more than a carbon steel like 1095).

As far as differences in time, I don't have any O1, but I do have 1095 and other carbon steels as well several models in M4, and yes really the only difference will be time/number of strokes to gain a the level of sharpness you're after, for me I go for high edge retention steels because I prefer to sharpen less often. There are things that can help you short the time difference such as diamond stones instead of using a whetstone when sharpening the higher carbide steels. I see it as a question of do you want to sharpen your knife for 10 minutes once a week(1095) or 20 minutes every two weeks(S30V) or 40 minutes (S90V)but just once a month given the same blade geometry, good heat treat, and same use. Of course that's just an example I made up off the top of my head S90V may only take half an hour or 20 minutes depending on your skill and sharpening equipment, or your 1095 may be able to go a week and half, etc.

cm_bushman · May 23, 2013

Thanks guys, I have always wondered if the carbon steels had some X-factor that made them the dream to sharpen that everyone always talks about. I think I'll go with O1 after all, it seems a good steel and I've had no rust problems so far with my carbon knives. If I ever do, I'll know that stainless is the way to go from there on.

yoda4561 · May 23, 2013

Low wear resistance, fine carbides(due to low alloy content), resistance to burr formation, these aspects come together to make carbon steels VERY easy to get a sharp edge on compared to "cheap" stainless alloys. Some stainless alloys can have similar properties, I actually find the harder the stainless the easier it is to sharpen, due to resistance to forming a large burr and better feedback on the stone (soft alloys like 440A/chinese kitchen knives tend feel rubbery and don't glide across some stones well).

Edit: I used to have an M2 AFCK, M2 and M4 have superb wear resistance, but again they also have relatively fine carbides and are run VERY hard which prevents a floppy burr from making sharpening difficult. M2 takes a bit of work if you let it get dull due to the hardness and wear resistance, but once you get past the initial reprofiling it takes an edge that few knives I've seen have rivaled.

Shotgun · May 23, 2013

I've had a 1095 and a 3v in scandi. For convexed and flat I've had S30V, INOX, 1095, SR101, and O1. I sharpen all of them with sandpaper and a strop. The S30V takes a little longer to sharpen but not by much but then I don't let them get too dull before touching them up. If I were in the market for another scandi I wouldn't hesitate to go with a higher end steel. 3V is pretty awesome if it's an option.

HwangJino · May 23, 2013

I started out with carbon Yanagi's and just learned to prefer them.

I've heard many a chef say stainless is for children.

Carbon knives require more wiping, say you work in a restaurant or something, as carbon is prone to rusting and stains.

I also know how to force patinas using either acidic (lemons) or blood (I'm assuming iron causes blue rust?) as tuna blood or beef blood gives carbon a beautiful blue hue.

Acidity turns carbon grey/black depending on exposure.

Also, not all steel or carbon steel is created equal.

I have used good quality carbon yanagi's for a while, but have been given the privilege to test a true honyaki (pure carbon is hammered for months to bleed out impurities) Yanagi and let me tell, it cut food like it wasn't there.

A hot knife through butter would be an insult, as you could feel butter.

Sadly most of you will never have the option of cutting food with a $4000+ knife, the type of steel exists.

leifjl · May 23, 2013

i didnt read this whole thread, so if somebody already said this just ignore. tool steels can be stainless or not. 01, d2, and m4 are all tool steels and they sharpen very differently from one another. harder to sharpen usually equates to carbon, chromium and tungsten content of the steel. a really high percentage of any of these in a steel will make it more difficult to sharpen.