Thread: Video: How Much Steel Hardness Affect Honing ?

Recently a gentleman commented on honing video in my YT channel, I was honing Towa Tungsten Steel razor on A Maruoyama JNat… The person inquiry was “is it really the steel hardness or the stone cutting powers that causing the slowness”.
In that particular case, it was a combination of both, the stone has a reasonable cutting powers for a finisher, however with such hard steel and the stone surface smoothed out; the Maruoyama stone and the Nakayama slurry turned into a slow finishing combination, also the color of the base stone made it look worse than it was.




The gentleman question encouraged me to compare the hardness of different steel alloys of common razors, I didn’t pick any exotic Steels like Tamahagane, Tungsten Steel or even Swedish Carbon Steel; I intended to show that even with common European steel you can make some abrasives fail or behave differently.
In the comparison, I have used a super polished light Nakayama Asagi as base stone, and the slurry was 100% natural Saudi Pottery Clay, produced in the central region in AL Majmaah to be exact ( currently, the only information I have is that they find it 10 meters under the ground as veins ).
The razors I choose:
Henkel inox
Solingen Silver Steel
Spanish Carbon Steel “Koken by Fabricacion Española, in other word it is a cheaper version of a Fily”




This is sometimes the hidden reason behind the conflicting opinions about one type of abrasive.


Happy Holidays,

Good point. I believe it is more often than sometimes the reason why there are conflicting opinions, personally. Not only in the steel removal rate, but in the comfort level of the edges as well.

100% agree with you, I think the two are related, if you have softer steel the abrasive will remove metal faster and will dig deeper into the steel leaving semi-mirror finish, with harder steel the edge will take mirror finish and maybe smoother edge, such effect is exaggerated in Japanese laminated steel; the harder core take super mirror finish where the softer external layer become hazy, however this also depends on the abrasive material itself and it hardness.... when Aluminium Oxide abrasive is used the contrast between the two layers disappear; as any steel is soft steel for such aggressive abrasive.

My video is not working.

Originally Posted by Gipson

My video is not working.

Fixed, you can watch it now, thanks for alerting me.

The last video is non existent. First I'd like to comment on "swedish steel", over the last 200 years or so there have been so many steel manufacturers in sweden its not even funny. And they have made so many different steels its impossible to classify a steel as just swedish steel imo. It could be anything from 1095-ish to o1-ish to any tool steel or any strip steel or band saw steel. Its like saying you have an american car. Oh really, which one? An american one...

Pretty much all abrasives are harder than martensite, since martensite tops out at 64hrc or about 1000HV or so, and if you add more carbon to the mix oversaturating the steel you get more hardess but not from the actual martensite/the matrix but now from carbides and cementite I suppose . If you add alloying elements that have an affinity for carbon you get carbides that are much more abrasion resistant (harder) than iron-carbon itself. Most if not all carbides found in steel is harder than aluminum oxide, which I think it tops out at about half the hardness of tungsten carbide for example (or even lower). Even chromium carbide is harder than the alu oxide iirc.

If you put lets say more than 0,5% tungsten in the steel you will get hard carbides, up to that point it acts more like a grain refiner, another common grain refiner is vanadium, and if you put in more than like 0,1% of that you get lots of hard carbides. In the US they prefer to put vanadium in steel since they have lots of that type of ore, in japan they have tungsten rich ore so they use that.

The most problematic steels to grind are the ones with several % of either V or W, since now you have a fine grained steel, with lots of finely distributed carbides that you can't cut even with silicon carbide, and the carbides reside at the grain boundaries, so your only hope is to abrade the steel matrix supporting them until they simply fall out. It gets worse if you temper these steels at hss temperatures since there are 2 different carbides formed in the steel (primary and secondary ones), and the one produced after a high temp tempering are harder to grind, but the matrix gets softer though... and hardness of the matrix is directly equivalent to strength.

If you're unlucky you can have the worst of two worlds all in one single piece of steel Impossible to grind large multimetal carbides suspended in a weak but tough matrix.

About 10 years or so ago a steel called s30v showed up, full of V (4%) Mo (2%) and 1.45% C, total nightmare to grind/sharpen if hardened to its full potential. Unless you have diamonds. Usually you can't even polish it well.

If you want easy to hone steels, avoid everything with W or V in it. Especially when the description of the steel is so vague as it is with razors. Thats my recommendation.

We agree there as well AK. And excellent summary, jigane. Metallurgist, or knifemaker?

Originally Posted by eKretz

We agree there as well AK. And excellent summary, jigane. Metallurgist, or knifemaker?

Ex machinist and now mechanic, but I like making some knives from time to time and HT/metallurgy is one of my hobbies that I read a lot about, like books. Since I have to know all this to make high performance knives. Or in my case select half finished blades and so on (I dont have my own grinder or HT furnace, YET..). Will probably get a KMG and a Kanthal based furnace this year though. Right now I'm into kitchen knives.

I'd like a charpy tester and hrc tester too and if I'm lucky I can find these locally.

Yeah btw what I meant to say with the long boring post above is that alloying elements chosen and the amount of those probably matters a lot more than the measured hardness when talking grinding/honing/sharpening/polishing.

You can effectively have a steel with a soft matrix and lots of big multicarbides, a hard matrix with lots of carbides and a plain carbon steel full hard and they will all have the same hardness, but will definitely not hone the same. Nor wear the same or degrade in the same way.

And V is the worst and W is like no 2. Maybe rhenium or niobium makes worse "problems" but those are so expensive to put in steel so they are almost never used anyway. Niobium is a good grain refiner though.

I like o1 steel though (in knives). Hard enough, tough enough, stain resistant enough, and takes a really retardedly sharp edge, and its easy to mass produce well. And it sharpens up quick almost like 1095, whats not to like here??

Originally Posted by AljuwaiedAK

Recently a gentleman commented on honing video in my YT channel, I was honing Towa Tungsten Steel razor on A Maruoyama JNat… The person inquiry was “is it really the steel hardness or the stone cutting powers that causing the slowness”.
In that particular case, it was a combination of both, the stone has a reasonable cutting powers for a finisher, however with such hard steel and the stone surface smoothed out; the Maruoyama stone and the Nakayama slurry turned into a slow finishing combination, also the color of the base stone made it look worse than it was.




The gentleman question encouraged me to compare the hardness of different steel alloys of common razors, I didn’t pick any exotic Steels like Tamahagane, Tungsten Steel or even Swedish Carbon Steel; I intended to show that even with common European steel you can make some abrasives fail or behave differently.
In the comparison, I have used a super polished light Nakayama Asagi as base stone, and the slurry was 100% natural Saudi Pottery Clay, produced in the central region in AL Majmaah to be exact ( currently, the only information I have is that they find it 10 meters under the ground as veins ).
The razors I choose:
Henkel inox
Solingen Silver Steel
Spanish Carbon Steel “Koken by Fabricacion Española, in other word it is a cheaper version of a Fily”




This is sometimes the hidden reason behind the conflicting opinions about one type of abrasive.


Happy Holidays,

Basically, a well know fact, one stone can't do it for all steels. That is why one has to have a bunch of options to cover the spectrum. Also it is a lot more fun to have more rocks to play with.