Hard Jnat polishing tips?

[KenjiF]

Hi folks,

Looking for any tips on using hard fine stones. The ones they warn you you’re not ready for and you buy anyway…

Just finished a polishing session today with a 5/5 and it was… humbling

I’d start and see some amazing results coming through then I’d hear the crunching sound look down and see scratches I’d have to go back to 3k to fix. Cleaned everything, atoma 1200 to bring up some mud, plenty of water, light pressure. I repeated this about 5 times till I put the knife down. I was working on a Raquin KT so there was a lot of convexity which prob wasn’t helping. Id notice it would turn dicey near the shinogi but not sure what I’m doing wrong… I thing it’s grabbing and scratching not contamination if that helps…

 

[refcast]

At risk of possibly cracking, run surface under hot water or warm water. Hotter works faster. Try stone. Stone surface will slurry more but fineness will remain the same. Crunchies should reduce. Repeat until it gives the feedback you like. This has worked for razor stones for me, even the super hard karasu, which are about the hardest that stones get. Otherwise, wash everything and repeat to remove contamination. Dish soap as a surfactant during sharpening can help suspend grit and reduce friction

 

[KenjiF]

At risk of possibly cracking, run surface under hot water or warm water. Hotter works faster. Try stone. Stone surface will slurry more but fineness will remain the same. Crunchies should reduce. Repeat until it gives the feedback you like. This has worked for razor stones for me, even the super hard karasu, which are about the hardest that stones get. Otherwise, wash everything and repeat to remove contamination. Dish soap as a surfactant during sharpening can help suspend grit and reduce friction

Awesome! I’ll give it a go.

 

[ethompson]

I'll chime in since I know the stone you're talking about.

How old is your 1200 atoma? I had nothing but problems with mine shedding diamonds when raising a slurry until I'd thoroughly worn it out, more so than my 140 and 400. Give it a go without raising a slurry to start as well. Start with lighter pressure focused primarily on the iron until you get a grey slurry working and then keep working moving the steel into the line of fire as well.

Worth giving the stone a really good scrub with a sponge or brush too to remove anything that maybe got lodged into the surface of the stone in storage or shipping.

 

[KenjiF]

I'll chime in since I know the stone you're talking about.

How old is your 1200 atoma? I had nothing but problems with mine shedding diamonds when raising a slurry until I'd thoroughly worn it out, more so than my 140 and 400. Give it a go without raising a slurry to start as well. Start with lighter pressure focused primarily on the iron until you get a grey slurry working and then keep working moving the steel into the line of fire as well.

Worth giving the stone a really good scrub with a sponge or brush too to remove anything that maybe got lodged into the surface of the stone in storage or shipping.

Oh that makes sense. It’s almost brand new… I had much more luck with a kiri just now and I barley raised a slurry with the plate this time so maybe that was it. I will give it another go tomorrow. It was really silky feeling w great feedback until it was catching so a loose diamond makes sense.

 

[Rangen]

Second the advice to use a worn-out plate if possible. Here's a worn out 3M 400 plate at 60x. Flat and benign, but still makes great slurry.

Here's an Atoma 400 with not all that much use:

Hard to see 3D-ness perfectly under the microscope, but one can tell that there are little 3D mountains of diamond with potential for mischief.

I don't have a pic, but the Nanohone NL-10 looks almost exactly like the worn-out plate, except of course that its benign flatness is renewable.

 

[KenjiF]

Second the advice to use a worn-out plate if possible. Here's a worn out 3M 400 plate at 60x. Flat and benign, but still makes great slurry.
View attachment 249782
Here's an Atoma 400 with not all that much use:
View attachment 249783
Hard to see 3D-ness perfectly under the microscope, but one can tell that there are little 3D mountains of diamond with potential for mischief.

I don't have a pic, but the Nanohone NL-10 looks almost exactly like the worn-out plate, except of course that its benign flatness is renewable.

Nice! I have the NL-6 may be worth giving that a try. Thanks mate!

 

[refcast]

Oh jeez. Yeah a new atoma is definitely contributing to the scratching. One thing about hard stones is that, the sharp edges or gogues left by diamond plates on the stones, those can lead to stray scratches. I think because it's a sharp edge on the stone, which breaks off like a coarser particle. Use lighter pressure too, and of course a worn plate helps.

 

[ReiHamono]

It’s pulling iron

I would use atoma 600 or worn atoma on the surface, rinse very well, then soak in hot water, then try with micro strokes being sure to keep moving over fresh stone every stroke

If you feel it start to grab iron you can try twisting away from it, sounds strange, but I had one stone where this worked perfectly or just lift up and restart

Ultra slow process, but burnishing always is

Hi folks,

Looking for any tips on using hard fine stones. The ones they warn you you’re not ready for and you buy anyway…

Just finished a polishing session today with a 5/5 and it was… humbling

I’d start and see some amazing results coming through then I’d hear the crunching sound look down and see scratches I’d have to go back to 3k to fix. Cleaned everything, atoma 1200 to bring up some mud, plenty of water, light pressure. I repeated this about 5 times till I put the knife down. I was working on a Raquin KT so there was a lot of convexity which prob wasn’t helping. Id notice it would turn dicey near the shinogi but not sure what I’m doing wrong… I thing it’s grabbing and scratching not contamination if that helps…

 

[Blank Blades.]

It’s pulling iron

I would use atoma 600 or warn atoma on the surface, rinse very well, then soak in hot water, then try with micro strokes being sure to keep moving over fresh stone every stroke

If you feel it start to grab iron you can try twisting away from it, sounds strange, but I had one stone where this worker perfectly or just lift up and restart

Ultra slow process, but burnishing always is

I agree. This is exactly what i was thinking.

Usually if my grit is contaminated i know right away. It doesnt happen after i have been using it for a minute.

But the adhesive wear between the iron and the stone definitely causes chunks of some stones to get pulled up like this if not very carefull. Doesnt matter how finely conditioned the surface. In my experience.

I've had this happen when flatten, then following with a synthetic nagura, then following that with natural naguras to condition the surface. Then cleaning the stone after all of that (and in between steps). So it definitely doesn't just happen when the surface is rough.

 

[Rangen]

Nice! I have the NL-6 may be worth giving that a try. Thanks mate!

NL-6 is not like NL-8 and NL-10. It's an extra-large plate designed to flatten and lap stones more quickly, due to its shaping, but it's still at heart a conventional diamond plate, with diamonds bonded to the surface. At least that is how it looks; I do not have one. So I have no reason to expect that it would be that different from an Atoma, with respect to shedding diamond, or making deeper grooves in the stone.

NL-8 and NL-10 are a whole different world, consisting of buttons in which metal and diamond is mixed together, like a bunch of cylindrical metallic-bonded stones mounted to a thick plate. There is quite a thickness of diamond-metal mixture, so the lifetime is much longer, and the diamonds are not sitting proud and bonded to a surface, but just exposing a bit of themselves as the metal soup they're in wears away.

 

[OkayMode]

Sounds like others have already diagnosed your problem, but in the meantime I have had good experiences using a natural nagura like this one for raising slurry rather than an atoma:

https://protooling.com.au/products/morihei-japanese-whetstone-nagura-natural-stone
If you use a bit of pressure they’re actually pretty fast.

 

[Blank Blades.]

Sounds like others have already diagnosed your problem, but in the meantime I have had good experiences using a natural nagura like this one for raising slurry rather than an atoma:

https://protooling.com.au/products/morihei-japanese-whetstone-nagura-natural-stone
If you use a bit of pressure they’re actually pretty fast.

Yeah. Honestly a lot cheaper to just get a nagura

 

[KenjiF]

Thanks for all the advice folks! Much more successful session testing Kiridashi this morning. Dressed with atoma 1200, cleaned everything with a brush and warm water, 10000 grit synthetic nagura (Tsushima nagura on way), cleaned again w warm water and brush, worked iron until I start seeing swarf/slurry, moved to steel. The stone is cutting and burnishing now and I can put more pressure on the blade without it grabbing or crunching. I think it was a mix of both grabbing and contamination I was dealing with. The large scratches I think were loose diamonds which I saw none of this time but if not enough of my bevel was in contact w the stone (too much pressure on shinogi) it would grab with smaller scratches this time as well. Definitely easier w a kiri than the KT grind on Raquin. I’m going to test with a flatter grind knife tonight (as much as I want to see what’s hiding in Bryan’s cladding). Kiri’s are bright mirror now with contrast and detail that I haven’t seen before. Thanks for the troubleshoot!

 

[ethompson]

Once you get the slurry worked up I’d suggest using less pressure not more, especially on soft iron. That stone can burnish and polish depending on how you manage pressure and slurry.

Another thing to try is using a spray or drip bottle with just a bit of washing soda or glycerin in the water. Helps break surface tension and manage harder stones IME

 

[ethompson]

I’ve used that stone in Bryan’s vintage iron and xc10 and didn’t have issues with it tearing at the iron, so I think your problem was probably the atoma 1200 shedding diamonds and eventually you got slurry with that diamond under the blade as you went. I only use my 1200 for burnish a stones surface after flattening anymore. If I’m raising a slurry for some reason I’ll use my totally worn 400 with much better results than my 1200.

 

[KenjiF]

I’ve used that stone in Bryan’s vintage iron and xc10 and didn’t have issues with it tearing at the iron, so I think your problem was probably the atoma 1200 shedding diamonds and eventually you got slurry with that diamond under the blade as you went. I only use my 1200 for burnish a stones surface after flattening anymore. If I’m raising a slurry for some reason I’ll use my totally worn 400 with much better results than my 1200.

Thanks @ethompson I’m excited to learn what this stone is capable of. Let me clarify what I meant by the experience of the Raquin. I don’t think it’s the iron or the steel that was causing me issues but my skill polishing the convex grind. I think what was happening is my pressure was too high and when I was shifting angles for hamaguri polishing. As less material was in contact with bevel with the same hand pressure the bevel that was touching experienced more pressure because it was focused on a smaller area and it grabbed. I think I need to do better shaping the transitions earlier and learn to ease up pressure whenever I move angle. This is all conjecture and will test again tonight making sure the stone is diamond free… I don’t have a 400 let alone a worn one but it’s on my list. Have you ever used the really small nagura sized ones? Tosho has them and I was waiting till I order something substantial from them to justify the shipping…

 

[ethompson]

Thanks @ethompson I’m excited to learn what this stone is capable of. Let me clarify what I meant by the experience of the Raquin. I don’t think it’s the iron or the steel that was causing me issues but my skill polishing the convex grind. I think what was happening is my pressure was too high and when I was shifting angles for hamaguri polishing. As less material was in contact with bevel with the same hand pressure the bevel that was touching experienced more pressure because it was focused on a smaller area and it grabbed. I think I need to do better shaping the transitions earlier and learn to ease up pressure whenever I move angle.

Not to worry, we're on the same page and I think your self diagnosis is accurate!

With something with as short of a bevel as a Raquin, the overall convexity is likely to me fairly minimal. Enough that you should be able to maintain it with finger placement changes rather than conscious angle changing fwiw.

I haven't used the small atomas. But I also typically don't raise a slurry, even on very hard and fine stones. I prefer to let the stone do the work the vast majority of the time. And I am raising slurry I typically will use a tomo nagura of equal or finer fineness.

 

[user 16756]

Learning to use the right amount of pressure on hard stones takes time and it's almost always less than you think.

Less than that.

No, even less than that.

Forced slurry and naguras change the results. Maybe you like it better, maybe you don't. For me it's very dependent on the specific stone, but in general I think that IF you can get a really even polish without slurry from a plate the results tend to look better to my taste.

BTW a small tip from this maybe sorta decent polisher is something what works well for me is I put the thumb of the hand that's holding on the same plane I want to be polishing as the fingers Im using to push the knife over the stone. I find this helps me stay at the right point of the bevel even with light pressure.

 

[KenjiF]

Went back to gesshin 2k, eased the transitions, 3k chosera, aizu, Kitayama, hard suita and narutaki on the Raquin. Followed the tips from above and had way better results. First pass was with warm water, a little dish soap and a super worn atoma 140 dressed with a synthetic nagura, cleaned and worked on iron till I got a bit of slurry and eased pressure and worked whole bevel. 2nd pass I dressed with atoma 1200 followed by a 10k synth nagura and scrub clean. Water and dish soap super light pressure and focused on burnishing. No grabbing or crackling on the stone. Not perfect but miles better than yesterday. Big thanks everyone. I can’t imagine how long it would have taken me to figure this out without the help.

 

[Heckel7302]

Looking good! Perfection is always to be strived for, but rarely attained.