Thread: Natural hone for setting the bevel?

The numbers for the Iwasaki razor are about right, this thread shows one (factory tested by the maker) at 860 HV (https://straightrazorpalace.com/cust...tml#post740753) which converts to about 65 HRC, it is the same razor OZ referred to above.

67 HRC seems to be the upper limit, this thread, @ post 14 reports knives at 66-67 HRC (https://straightrazorpalace.com/razo...uestion-2.html).

F.Dick precision files are rated the same (see https://www.fine-tools.com/feile2.html), the steel used here would not be dissimilar to that used in razors

In both cases it would be safe to assume that the manufactures have put in considerable effort and great expense to get the knives/files as hard as practically possible, the knives likely for bragging rights and the files for superior performance.

I guess my point is already made. The claim that some razors were hardened "at or over 67 Rc" is unsubstantiated and very unlikely. I have no problem with a claim of 64/65 Rc. Testing a razor at or even near the cutting edge is virtually impossible because the steel is too thin for an accurate test by any method I've heard of. 67 Rc is the absolute tops I've ever heard of for carbon steel, and that's basically with zero tempering, which makes for extreme fragility. With a razor production attempt at this level, one would be likely to scrap most of the production due to cracking of the blade during heat treat. Any knives harder or even probably most of the knives at this level are likely alloys similar to ZDP.

Originally Posted by eKretz

67 Rc is the absolute tops I've ever heard of for carbon steel, and that's basically with zero tempering, which makes for extreme fragility. With a razor production attempt at this level, one would be likely to scrap most of the production due to cracking of the blade during heat treat.

In fact Iwasaki stopped using tamahagane because 50% of the razors did not meet his high expectations & were scrapped. The ones in circulation are gems.

Just to prove that I did not imagined it, and mainly to myself to be honest, but sharing my results won't hurt, here are the three threads searching for " HRC 67 " in the forum
https://straightrazorpalace.com/auct...ern-style.html
https://straightrazorpalace.com/honi...ds-honing.html &
https://straightrazorpalace.com/begi...bly-blade.html

You are right about the files too, I have read that they are tempered that high. Or close to that. I'm not starting any heated arguments, nor did I intend to from the beginning. I just said that I've read about the existence of such razors somewhere, quite possibly above. Where, again, I'm not blaming the ones saying it, I bet there were such razors/knives/files-pieces of steel.
An hyperbole for going higher than that as it turns out, so, I'm sorry everyone!
My original point was "razor are made to be hard". Also, scratching a razor is easy, even wiping one from common relatively-non-abrasives-containing dust could do it. But you can also scratch glass with a corner from a piece of calcite (crystallized CaCO3/calcium carbonate); the Calcite will be destroyed, and a tiny line will appear on the glass, that's not real scratching nor true Mohs hardness testing. I have done the exact above thing, that's why I'm mentioning it.
The DIY Mohs hardness test can be used for knives although the results are subjective; take a knife you know is tempered to above 50 and scratch another one, on the side (no clad steel, san mai and all that stuff, just a classic "monosteel" knife) with the tip to the side of the other, in a way that you'll do the minimal damage to the "known" knife but you will be able to see/feel the knife you are holding biting into/hear the other knife giving in and then feeling the line with your finger. It's an invasive method for sure, but if you don't have any other choices it answers the question "is that piece of steel any good?" quickly. If you are a blacksmith in your smith though, there are far far better options.
By the way I think we went quite off topic.

Originally Posted by Vasilis

By the way I think we went quite off topic.

I think we did. The topic was natural hones for bevel setting

By the way, as a fellow from Cyprus, the word in Greek for sandstone is Psammite/ψαμμίτης.
With a quick google search you might find something interesting quarried locally in Cyprus.
It's not a rare material, the difficulty is to find the correct particle size, abrasion resistance-you don't want the stone to give the particles easily otherwise it would be either coarse or will have a short "lifespan", the lack of inclusions, be that coarse particles or lines that break easily and are leaving big pieces in the slurry, anyway, you want something that feels honing-friendly.
When you find, lap it nice and good until flat, sandpaper on a piece of glass the easiest way, AND FIRST TEST THE STONE ON A CHEAP KNIFE! Don't use a filarmonica 8/8", you'll go to razor hell. And again, when you do find some, I want a piece or two!

Originally Posted by onimaru55

In fact Iwasaki stopped using tamahagane because 50% of the razors did not meet his high expectations & were scrapped. The ones in circulation are gems.

I don't blame him. It would be mightily frustrating to see half or more of one's hard work thrown in the scrap bin with every batch produced.

I used to and still occasionally use a Washita. I have an old 4x12 monster that was passed on to me by a family member. Newer ones are not as good. I think Norton closed down the quarry they once used. And off topic it’s not the hardness that is the gremlin on using naturals but the wear/abrasion resistance of the newer modern alloys that can make it a pain. If you take A2 and 1095 to the same Rc the A2 is still going to take longer to sharpen

Originally Posted by CrownCork

I used to and still occasionally use a Washita. I have an old 4x12 monster that was passed on to me by a family member. Newer ones are not as good. I think Norton closed down the quarry they once used. And off topic it’s not the hardness that is the gremlin on using naturals but the wear/abrasion resistance of the newer modern alloys that can make it a pain. If you take A2 and 1095 to the same Rc the A2 is still going to take longer to sharpen

You are partly right, some alloying elements do make steel extra wear resistant, first element that comes to mind being Vanadium. A CPM S30V knife I bought is a PITA for example, and there are many even less hone friendly steels out there. But hardness plays a very important role too.

Edit to add a bit more detail, without the heat treating, an alloying element does not form the carbides that add the extra wear-abrasion resistant effect. That's why you can't have them, and their effect without the hardening and hardness.

Any steel alloy that forms any significant amount of the harder carbides during heat treat (tungsten, vanadium, chromium, etc.) will be the devil to hone with a natural stone. Trying to hone plain carbon steel hardened to a high level (65Rc or higher) would probably fool most people into thinking they were honing one of these alloys. Both play a significant role in difficulty of honing, but the hard carbides are particularly nasty.

At the coarser level, natural stones can still cut around these carbides, but in many cases this amounts to basically eroding the steel matrix around the carbides until they fall out. Even synthetic stones have trouble cutting the harder carbides, and synthetic abrasive are considerably harder than most of those found in most natural stones.