Honing on extremely hard jnats

[JPO]

That is one of the reasons why I recommend a tomo over diamond plate. Diamond plate for slurry definitely has it pros, but my preference still falls with tomo naguras.

I think it is quite common to use a tomo nagura slurry after a DN slurry. The DN is not a replacement for a tomo nagura.
If synthetics are used up to 8k you only need a light tomo slurry.

You can also break down the DN slurry with a tomo nagura. Finding a good matching tomo nagura for a super hard stone can be difficult if the vendor have not done it for you.

I have cut tomos from stones that did not work well with the host stone they were cut from.
So, you might have a good base stone, but your tomo nagura might be limiting the potential of the base stone. If the tomo is scratching the base stone you are not going to get good results.
So, there is allot of different variables that come into play.

Understanding the breake down mechanism of a diamond plate will not help with the practical use of that plate. Fracture mechanics of brittle materials is a interesting subject, but it is way over my technical level, and I have worked with steel fatigue professionaly.
I think the science of sharp blog covers this from a practical point of view.
Atoma plates and DMT plates will not breake down/in the same way due to the difference in the way the diamonds are applied to the plates.

All these plates will produce a different type of slurry.
Broken down DMT 600

Atoma 400 with some use

Atoma 1200 with some use

 

[Steve56]

I think it is quite common to use a tomo nagura slurry after a DN slurry. The DN is not a replacement for a tomo nagura.
If synthetics are used up to 8k you only need a light tomo slurry.

You can also break down the DN slurry with a tomo nagura. Finding a good matching tomo nagura for a super hard stone can be difficult if the vendor have not done it for you.

Good advice, and basically what I do, though I usually use koma or gujyo before finishing with tomo, if I do a pre-finish.

 

[Darth Scandalous]

Stones form the platform so that stropping can be more efficient and precise.

Here is wisdom.

(the rest of the post, too. But especially this).

 

[rhgg2]

I find that the silica dioxide and alumina oxide playground of "4k to 20k" grit is mostly a moot point when you or I, and we all do when we include A Stropping Regime.

One of the more enlightening experiences I had was to shave off a razor honed as follows: Shapton 1k, 3k, strop like the blazes. It was very sharp and comfortable. It made me realise how subtle the effect of the further progression is, and that as a beginner there is a high chance of making things worse rather than better!

 

[Gamma]

What a lot of people miss is that just because person A can't sense a tremendous effect of honing after XYZ k, or whatever,, that doesn't mean others have that same impression.

It's been claimed that most sharpness is developed at 5k or a bit higher, so maybe 8k.
That's actually the entire bevel set process, honestly. Edge width is not the whole story though.

A practical difference in sharpness between a so-called perfect 3k and perfect 8k edge (same razor, same bevel set) might be difficult to discern via measurement; edge width will be very close. But someone that has been paying attention to their sharpening and shaving would, or at least should, normally and easily sense a big difference there, and sense and even further gains as continued refinement is achieved.

Experiencing the scenarios and their differences repeatedly might shed more light on the subject. I cycle through shaves from various parts of the progression regularly. Earlier in the week I shaved with a 1.5k edge and then the same razor with a 4k treatment. Tonight I shaved with the same razor brought up to 8k. There were significant differences at 4k and between 4k and 8k too, as expected.

IMO, if someone can't see much difference between 3k and down the line, then I'd assume they probably didn't establish their initial bevel set to max. Without that in place, attempts to refine to max will peter out. That's why some can't seem to increase cutting efficacy much after a certain point. In those cases, sure, chasing higher grit finishes won't deliver much of a ROI. But when done right, there are big differences between, say - a 15k and 20k Gokumyo shave.... when all else is on point and equal. Especially when the 20k edge was set up by that 15k....

Sharpness is only a tiny factor, there's a lot more to cutting quality than just edge width. Stropping a turd doesn't make it better, stropping a plum does though.
Stropping is just healing that stones or abrasives can't handle. Nothing else. If you put a bandaid on a cut it'll probably work, but put one on a gushing artery, maybe not so much. Ideally, we want the bandaid/cut thing....gushing arteries need to go back to earlier grits to be healed correctly. Stropping well is like choosing the correct garnish.

As for DN slurry, meh... never got into it. Initially they (DN's were a work around promoted by sellers who didn't have Tomo to sell. Then it was promoted by those not wanting to buy Tomo. I never found it to be useful. Adjusting slurry density has always performed better. I rarely have a need for coarse slurry from a DN or thick slurry from a Tomo though. I still have a DN, but I use it to sharpen a very small chisel mostly.

 

[alx gilmore]

Why have men for untold centuries continued to stropping their already "stone sharpened" blades on leather? There is only one answer; To make them sharper!

I quote Keith:
Sharpness is only a tiny factor, there's a lot more to cutting quality than just edge width. Stropping a turd doesn't make it better, stropping a plum does though.
Stropping is just healing that stones or abrasives can't handle. Nothing else.
End quote.

At a microscope level stropping on a hanging leather abrasive encourages the 'flat well-formed apex' of an edge to be slightly convex, thus thinner than a flat honing stone can make it. This is why we use strops.

Stropping leaves the bevel slightly convex to the degree, and it is the slack of the strop that determines the adjustment to edge convexity. This convexity helps to relieve the suction that can occur between the skin and the stone leading to a comfortable shave. A stone's slurry can also do this but not to the degree of craftiness that a hanging strop can where the operator finetunes and determines the virtues of the routine. I do not have to tell anyone who shaves with a straight razor that these are the reasons why all of use strop the edge just before we shave. The silica packed in the leather by the tanner is our agent
This mechanical reduction can only happen if an abrasive like silica, that is harder than steel is present.

Quote Keith:
Stropping is just healing that stones or abrasives can't handle. Nothing else.
End quote.

I agree with Keith on this point when he states, "Stropping is, when successful, a mechanical reduction of steel.

 

[rhgg2]

After thinking about the helpful advice I've got here I have finally managed to get a decent edge off a very hard stone, my big black bench jnat, possibly Ozuku.

I went 1k -> suita -> finisher. The first time I tried the finisher with atoma 1200 slurry only. This was enough to verify for me that the slurry does cut, not fast but not particularly slow, and there is abrasive in the stone. The shave off this was not great however.

So I redid the progression using tomo slurry on the finisher. The tomo is a piece of Nakayama Aisa which I find it quite hard to quantify the hardness of. It is a bit softer than the bench stone to be sure.

My thought was: since the stone cuts fairly slow, I should make a lot of slurry so that it doesn't break down before it has had chance to develop the edge. I should also have a lot of water so the slurry is not too dense. Then I honed for ages until the slurry was broken down, keeping it quite watery, and using only feather light pressure throughout. I ended by adding quite a bit of water and taking ten or so slow and ultra light laps. This turned out to be extremely successful.

One interesting thing is that raising slurry with the tomo was much easier after the previous slurrying with the 1200 atoma. So I guess one lesson is not to let the surface of stones like these get too polished and resurface regularly.

 

[alx gilmore]

rhgg2

Thank you very much for your enthusiastic post. Those dense heavy, dark, black stones are a form of uchigumori called Jizuya. They are used to polish the hard steel (ji) of a bi-metal blade, like laminated knives, laminated steel-iron swords or even razors. The carpenter's chisels or bi-metal aminated plane blades also have Jigane and Hagane metals forge welded to each other and then quenched in the coldest water the blacksmith can fetch.
When coupled with Hazuya (light colors and softer compaction) Uchigumori for katana swords or an array of bi-metal blades you can build a contrasting steel-to-iron demarcation pattern called the hamon. Black hazuya uchigumori will be slow cutting, thus the polishing effects. The attributes of Jizuya will create extremely keen blades.

You will want to get a close look at your edges as you progress on any one particular bladed tool when using uchigumori. Hagane will and can contain 55 to 70 percent silica dioxide, a fast-cutting mineral but less compacted than the jigane. Silica will quickly form the profile of your edges. Ji or Jigane on the other hand will contain a larger portion of aluminum oxide. The silica Sio2 will break down when confronting the Al2o3. This explains why some stones work better with some steel formulations than others. It also explains why some blacksmiths excel with and only use or mainly use certain steel formulas.

Alx

 

[Gamma]

One interesting thing is that raising slurry with the tomo was much easier after the previous slurrying with the 1200 atoma. So I guess one lesson is not to let the surface of stones like these get too polished and resurface regularly.

One of the main purposes of a tomo Nagura is to keep the working stone's surface conditioned. One definition translates to 'correction stone'.
Polishing a Jnat's working surface is not recommended. In fact, it is advised to not do that. An even continuous surface will perform best. When they glaze in spots, it is best to dress the top down.

If you have a good Tomo Nagura, you will find the slurry it makes to be the best choice for finishing. Of course the edge you bring to that slurry has to be where it needs to be. But if all is done well, the finer slurry can achieve a finer result and there's no chance, or need, to step backwards.

 

[rhgg2]

Thank you very much for your enthusiastic post. Those dense heavy, dark, black stones are a form of uchigumori called jizuya.

Thanks, Alex. This is the stone in question:

The dots on the surface are part of the matrix of the stone. Some of them are su-like holes.

 

[rhgg2]

One of the main purposes of a tomo Nagura is to keep the working stone's surface conditioned. One definition translates to 'correction stone'.
Polishing a Jnat's working surface is not recommended. In fact, it is advised to not do that. An even continuous surface will perform best. When they glaze in spots, it is best to dress the top down.

Yes I didn't mean actively polishing the stone, rather that a few rounds of honing and raising slurry had polished the surface enough that the cutting action starts to slow down.

 

[alx gilmore]

rhgg2

Thank you very much for your enthusiastic post. Those dense heavy, dark, black stones are a form of uchigumori called Jizuya. They are used to polish the hard steel (ji) of a bi-metal blade, like laminated knives, laminated steel-iron swords or even razors. The carpenter's chisels or bi-metal aminated plane blades also have Jigane and Hagane metals forge welded to each other and then quenched in the coldest water the blacksmith can fetch.
When coupled with Hazuya (light colors and softer compaction) Uchigumori for katana swords or an array of bi-metal blades you can build a contrasting steel-to-iron demarcation pattern called the hamon. Black hazuya uchigumori will be slow cutting, thus the polishing effects. The attributes of Jizuya will create extremely keen blades.

You will want to get a close look at your edges as you progress on any one particular bladed tool when using uchigumori. Hagane will and can contain 55 to 70 percent silica dioxide, a fast-cutting mineral but less compacted than the jigane. Silica will quickly form the profile of your edges. Ji or Jigane on the other hand will contain a larger portion of aluminum oxide. The silica Sio2 will break down when confronting the Al2o3. This explains why some stones work better with some steel formulations than others. It also explains why some blacksmiths excel with and only use or mainly use certain steel formulas.

How the wide ranges of silica and alumina interact with certain and sometimes exotic steels and wrought irons is what makes our hobby exciting. Exciting enough to sit and read this, and learn and argue and conclude upon these pages as we do.

Alx

 

[Gamma]

it's the same thing really, but when it happens during/from honing it can be more detrimental because it's scattered and intermittent.