How knives get dull...

Do you use different sharpening techniques for carbon steel vs. stainless steel? I have hunting knives of each and it seems like I get a much sharper edge on the carbon steel knife than on the stainless steel when using the identical sharpening procedure.

Small comment - from experience with good carbon steel - including chisels - it is possible to sharpen to creat a ''wire'' - and after that has departed the edge is amazing. Useage thereof tho and it's effects on edge durability will depend on steel quality and grade.

Stainless takes me longer to sharpen but - once done successfully will, if good material, hold an edge well.

Chipping is IMO indicative of bad heat treatment - excessive hardening to point of embrittlement. Edge bend or roll over is opposite - too little hardness thru possibly over temper. Corrosion should not be a factor with care on blade if steel. And, loss of edge by abrasion? Well -

One thing I try not to use my best knife for - is cutting cardboard!!!!

chipping occurs in all knives at some level. large chipping is an indication of poor heat treating/flawed steel. microscopic chipping is a major factor in dulling knives. edges will bend a bit too. just a little bit. a burr from sharpening is an example, they can occur on any steel at any hardness. so both will affect edge retention even with proper heat treating

its hard to do a direct comparision like that when there are many factors. i think a good alloy carbon steel beats out stainless for edge retention. not saying stainless is far inferior....in fact i prefer carrying stainless to high carbon.

As far as I know carbon steel is still king of the edge - none of the knives entered in the big cutting contest at Blade are stainless. There are guys like Loveless who make outstanding stainless knives, but properly heat treated carbon steel still has an advantage, IMHO. Some stainless steels are getting close though and it may not be long before some are equal to carbon steel. But it'll probably be very expensive and many will not use it for that reason.

one of the main reasons the big cutting contests are mostly high carbon steels is because they are hosted by the american bladesmithing society(abs) most forgers use high carbon steel since stainless is a pain to forge and doesnt benefit from it.
i think very soon we will start seeing stainless blades in them.

some of the testing includes a timed 2x4 chop, slicing through multiple filled water bottles, slicing through water filled popcans, chopping down top to bottom through popcans, stabbing ping pong balls, slicing through free hanging toilet paper, cutting wooden dowels, free hanging rope cuts, etc. they change challenges at different events, these are just the ones ive heard of. any damage to the edge at any time and the knife is disqualified.

it isnt geared just towards edge retention but also knife design, geometry, and the person wielding the knife is a major factor. make the right knife out of stainless and give it to the right person and i think they could win.

consider this...most steel cutting tools are nonstainless...milling bits, drill bits, router bits, planer blades(although many are made from d2 which is getting close to stainless) saw blades, metal bandsaw blades, etc. there is a reason for that.

again im not saying stainless is bad...half my sales are from stainless

I think a stainless knife in that contest is coming also, and soon.

My problem, I guess, is that the very best stainless costs so much. For now I'll stick with carbon steel (O1) that I can heat treat myself. I really like having control over the whole process!

Stainless is more likely to have the edge roll or bend, but the better stainless steels these days don't give up much hardness to the high-carbon alloys.

So, it looks like stainless is the clear winner in cat 3, a close winner in cat 2, a close loser in cat 1 and probably pretty much tied or maybe even a close winner in cat 4.

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I think you're confusing "stainless" with "high-alloy" steel. And it's really impossible to generalize those; like D2 is a semi-stainless high-alloy steel that's capable of taking an absolutely wicked edge, because the steel forms extremely large carbides, which makes a "saw-tooth" type edge under a microscope. This makes D2 an excellent choice for skinning, and other applications which require slicing type cuts through abrasive materials. But, it's pretty terrible at impact resistance, so it's a poor choice for chopping. The edge also tends to "crumble" more than bend, as the large carbides fall out (though if you make the edge thin enough, D2 can be self-sharpening to some degree).

On the other hand, 440 series steels are relatively bland. They've got carbon, chromium, and not much else. As a result, they behave quite similarly to carbon steels of the same carbon content, except they're a bit brittler (at the level of chromium where a steel becomes "stainless," it becomes brittler unless other junk is added to the alloy to counteract this) and more resistant to rust.

You can get plain carbon steels to get pretty varied characteristics just by changing the temper, too. Like a harder temper makes the edge more abrasion-resistant, but less shock-resistant and more likely to chip rather than bending. A softer one makes the blade springier and less likely to chip, but it will dull faster from both bending and abrasion.

It's possible to get a steel to have whatever edgeholding properties you want, if you add the right alloying elements to it, and heat-treat it correctly.


And those contests are almost entirely based on blade geometry and cutting technique. I remember reading about a guy that entered a knife into one of those things and went through all the tests with flying colors, until it came to the stick-the-knife-in-a-vise-and-bend-it-90-degrees test. Then he discovered that oops, he accidentally used mild steel for the blade!

i think there is a bit of politics/marketing involved in the cutting competitions..even if unintentional. most the makers that enter work either entirely or primarily with carbon steels. makers enter the events to prove their work (and to have fun and learn of course) if they were to make a stainless blade and win the event i think a lot of people would go "wow...stainless just beat all the high carbon." and have it in their mind stainless is superior. now they will wonder why does the maker work high carbon when stainless is superior?? not exactly good for business.

i think when they have big cutting contests where stock removal makers(stainless is used primarily by stock removal makers) compete in it a lot then we will be seeing stainless beat high carbon. not everytime of course but there are many factors in winning.

i think high carbon does hold an edge better, and it does give the competitor an edge...but if one competitor with a lesser knife has better technique he may trounce the opposition. it would be like me having a superb cutting high carbon katana and going against a profesional at sword cutting comps that had a stainless blade...no doubt in my mind he would whoop me.

my long winded point is....i think fairly soon we will be seeing some stainless blades win cutting comps...even though i think high carbon is better for them.

hso,
i made the mistake of generalizing on the abs/blade magazine cutting competitions...which to my undertsanding you have to be a member of the abs and wield a knife of your making in. please correct me if im wrong. if you have some leads on other cutting competitons i would be very interested in seeing the knives and people that enter and the results.

johnska,

Isn't there information on hardness, toughness, elasticity, etc.? I would think that quantifiable parameters like that would provide a far more useful basis for comparison.

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this is where the problem lies. there is much scientific information on steels but it isnt aimed towards the knife industry. most test done on knives are things like shaving, 2x4 chop, rope cutting etc..and arent exact. "the knife felt like it started to slide on cut #76" isnt very precise.

do a net search for catra tests to see some edge tests
here is some of their testing they do
http://www.catra.org/products/CATRATESTEQP.htm

I am no expert on sharpening,
but I believe that the NUMBER ONE REASON that neophyte bladesmen wind up wearing out their blades,
is that they do NOT understand the proper use of the sharpening steel to "touch up" a blade, as needed.
After mastering this skill,
I found that it was RARELY necessary to actuallly resharpen a bade,
after the blade was first properly sharpened in the first place,
which is often done competently at the factory.

I don't think it has been covered here - but what thoughts are there re the leather strop?

Re-sharpening by grinding does of course remove metal - but ''stropping'' instead dresses the existing edge. What do the knife guru's have to say on that?

The strop, or cardboard, or jeans as some guys use removes the burr that sharpening forms on the edge. I use some green buffing compound on a old belt.

I was thinking partly of the burr Don but - also thinking back (long ways!) to good ol' barber shop where the ''cut-throat'' razor would be stropped for every shave, and seemingly had a super edge. Way thinner of course being so hollow ground but - must sharpening per se by default, remove metal by gross abrasion?

Yea I don't know if stropping a knife between uses would help or not - couldn't hurt though. Sharpening steels are good for a touch up. I use a Spyderco Sharpmaker to sharpen my knives so it's easy for the owner to touch it up and keep it sharp.

I dont understand how people put their knives through things that break them...aside form the knives that have a 1" tang

Barber strops are more to realign the edge and "smear" it back into shape without removing metal, much like steeling. Hairs are actually tough enough to put (very small) dents in the blade. Leather by itself is only minimally abrasive, so some kind of cutting or polishing compound is necessary for stropping knives with a thicker grind.

Don and Ryan - thx.

Not sure if this is any help or not but here is my 2 cents on strops. I shave with a 7 day set of straight razors made of high carbon steel. when they get dull I use a strop to sharpen them up. I make optical mirrors as a hobby, so I generally have optical rouge and cerium oxide on hand as polishing compounds for the glass.

optical rouge is one of the oxides of iron. thermally decomposed ferric oxalate IIRC, it is by far softer than iron but will actually cause the surface of metal to flow a little, this is the same effect it has on glass. The effect rouge has on a strop is unreal. I have been using these razors for more than a year and have yet had to put them on a stone to sharpen them, a strop is more than adequate to get a good shaving edge. If all a strop did was deburr a blade, my razors would have been getting dull long ago, there is a definately a sharpening action going on. Cerium oxide has the same effect, but works a bit faster.

brerrabbit - sounds good to me! Thx.