Concerning Jnats: Is it me, or is it the stone

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DDPslice

DDPslice

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My issue has to do with polishing. I have a mizuno 240 hontanren clad with blue#2 the stone I'm concerned about is a Hakka koppa that is super soft (lv2) and the finish is a beautiful hazy-ness. Except, when I use the jnat, I get these intermitant large gashes in the jigane that I cannot buff out with uchigamori fingerstones. Feeling the slurry/mud I do not notice any hard grains, it is very smooth, as expected from the finish. But I do not know where the gashes are coming from. I've created the slurry from a DMT coarse plate, honzan, Torijo fingerstone, and from just working the knife to create a slurry. I am running out of ideas to test if it's me or the stone. I don't really deburr at this stage because I consider it a polishing and not a sharpening (is that wrong?), but my thought is that maybe this stone contains some quartz or other impurity that I cannot feel. Or am I creating a burr that is flaking off when I think im polishing but actually taking off more metal then I think and not realizing it? But I feel this is unlikely because of the hardness of the blue steel. The knife is sharp and I mostly use it for meats because it's so reactive, so I don't get a true feel for how strong/long the edge keeps unlike my SS that I'm constantly chopping veggies with. Any advice/suggestions would be greatly appreciated. Also, pics will follow, I just have to post them from my laptop when I get home.
 
How new is the Dmt? Any chance you are getting some coarse diamonds contaminating the stone? If I didn't have a substitute stone for the Hakka Koppa to check if it's the stone, I would a least try it without using the Dmt. It's soft enough to create mud without it.
 
That's strange.

It sounds like you've tried using it without a DMT slurry & still had that problem. Are there any lines in the stone that might be causing it?

FWIW I have the same issue with my Naniwa 8k Snow White and it drives me frickin crazy. I have no idea what is causing it to sound/feel/finish scratchy. And I know it's a clean stone & knife. So I sympathize. I have never had an issue like that with my Hakka though.
 
Have you thoroughly flattened the stone and rounded all edges and corners? The streaks or gashes in the finish could be from riding the edges of the stone. I also would try without the DMT. A coarse plate may dislodge clumps of particulate that act as large grains, streaking the finish before breaking down.
 
Dmt particles are known to flake off.
 
@MrMnMs
that was my initial thought because my flattening plate is wearing down and I thought that could be an issue, so i used my honzan which is a hard flat Jnat that can be used to flatten softer stones or a base for nagura slurries in the polishing process. Do you know if there is a warranty with the DMT plates or will I just have to bite the bullet and get an ATOMA or something of the like that's more reliable.

Btw anybody know the average life of the DMT compared to Atoma, is the latter worth that kind of price?

@JDA
yeah i feel ya, on my naniwa i just wasnt smoothing out the corners and that happened to me once on my SS 12k, which leads me to..
@funkmastaflex aka dmccurtis
yea that was my initial thought because of the Naniwa issue, but ive been flattening the corners and it all feels very smooth, like silk, and that's my confusion. (maybe something in the slurry is not breaking down like the other particles)

@theory
have you ever heard of the dmt particles getting imbedded in the stone, it seems possible because even though im creating a lot of mud the stone is very soft and something could get pushed deep down. But for the last 2 polishing sessions I've been using my honzan and naguras.(maybe i could be those because the soft steel is so soft)

aahhh...frustrating, it seems like i need to get a new flattening plate but I have no money to spend on my precious.

pics of me thinning it, it was think as hell, and still is.

edit
 
 
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Maybe I'm wrong, but I wouldn't think to use a coarse a plate on that stone. Try anything with a grit close to the stone, it might help you flattening or maybe helping built up a finer mud as well.
 
i would have to agree because i do not have a dmt fine, but the Honzan is a finishing stone so that should equal an extra-fine dmt.

to clarify the pics, the one with the towel in the background is when I was using the Hakka koppa to try and give that base hazy finish smooth out the King 1200, before I used an uchigumori fingerstone and 6K-8k sandpaper and baking soda slurry.

Any suggestions to the process and critiques, would be greatly appreciated as well.

corrections: @theory i meant to say the soft Stone is soft, so the particles could be lodged deep within

also the stone does have some imperfections, there is a black dot that has emerged right in the center, but this was happening before the dot appeared and yes there is a line on the top right corner but i purposefully polished on just the corner to test if it had any effect, but it did not thankfully.
 
That streaking looks like what happens when your mud gets too dry, or you use too much pressure. It frequently happens around the curve of the tip, since it's a lot harder to follow the contour of the blade road through the curve. I'd wager there's nothing wrong with your stone or plate (though you still shouldn't need to use a plate with a stone that soft). It's possible to achieve more consistent results with practice, but if you want a perfectly smooth finish there every time, that's what fingerstones are for.
 
dmccurtis said:
That streaking looks like what happens when your mud gets too dry, or you use too much pressure. It frequently happens around the curve of the tip, since it's a lot harder to follow the contour of the blade road through the curve. I'd wager there's nothing wrong with your stone or plate (though you still shouldn't need to use a plate with a stone that soft). It's possible to achieve more consistent results with practice, but if you want a perfectly smooth finish there every time, that's what fingerstones are for.
Click to expand...

are you talking about on the shinogi? Because if you notice on the secondary bevel towards the heel it has the smooth hazy finish but on the "face(?)" where the kanji is there are a lot of streaks/gashes. i did notice when the mud got dry i could make almost a mirror polish on the blade, i just figured those were low spots, or am I moving the blade too much/lack of control? I have been trying to go slower, with lots of patience.

i will keep that in mind when I polish tomorrow.
 
This photo shows well what I mean: https://docs.google.com/file/d/0Bwa1j-dlUS25ak00N3dIbzczRFNEYnNSTU1PaHVMN21aUjRz/edit. It's easier to get a smooth finish towards towards the heel, as the blade road is flatter. Through the curve of the tip, you're having to adjust for curvature in three planes (belly to tip, shinogi to edge, heel to tip), which makes it much more difficult to achieve a consistent polish. When polishing through the tip, ensure your mud is thick but fluid, and your final pressure is light.

As far as above the shinogi, were you trying to polish the blade face on the stone? If not, the streaking above the shinogi looks like you briefly tipped over onto the blade face.
 
I could show you a picture of a dmt plate I have where one whole corner has absolutely zero diamond particles left on it. Not saying this is exactly what you are experiencing but it's a possibility. Another possibility is the simple fact that with natural stones you have a variety of grits involved. More so, if the stone is of poor quality it could have toxic lines, inclusions or other particle irregularities which would be unwanted.
 
That's equally possible too. Every DMT I had before switching to Atomas wore like patchwork.
 
DD - I get over to Otown frequently. Happy to bring one of Jon's diamond flattening plates, full range of dmt and a couple JNats and let you play with them for a couple days. Of course there's a risk that may eliminate everything but operator error - and that can't be the case:angel2:. Drop me a pm if interested.
 
diamond stones plus naturals are really not a smart way to go... they dont condition the surface in a way that makes sense. You can use them to flatten if you must, but then you need to use a real nagura (natural not synthetic) to recondition the surface. Diamond stones leave deeper scratches at any grit level than their natural equivalents, which then cause weak spots to form around the ridges of the scratches, releasing more of the natural stone, and causing the finish to be less consistent and more coarse.
 
I agree with what JBroida wrote above, and I think there were a few other useful things said before. Here's what I thought:

1) You've got a soft Hakka, and it should be very easy to create slurry. No need for a diamond plate or even any nagura, in most cases. Sounds like you're applying some synth stone habits here and it isn't necessary.
2) You can maintain the condition of the surface, and its flatness, with nagura. As it's a Hakka, you might try a Tsushima nagura, maybe a mejiro, or one of those soft reddish ones JNS sells and calls a 'tomo' nagura. Or even a similar natural, like a normal Takashima, no matter what the size.
3) Use the diamond plate only in unusual circumstances, such as if there is strong dishing or if you're reshaping the stone (corners, bottom, etc).
4) The surface may be in rough condition from the use of the diamond plate, and larger pieces of stone may be breaking off, giving uneven slurry. You'll have to use the stone more, or condition with nagura, to smooth it out. As it is, you'll have to spend more time 'refining' the slurry as they say so that the big bits break down and smooth out. Don't rush the sharpening.
5) Could also be that this stone just doesn't give a smooth finish, due to harder parts in the slurry that don't break down. Or could also be a question of technique.
 
@daveb
Thanks for the offer!

@Jbroida
I figured as much, today I will only use my tomo nagura fingerstone, combining what Theory said about flaking and Asteger's #5 about impurities. I am trying to limit down the variables. And I guess this is the last step.
 
Scratchy and uneven finish, but looking more uniform in places. Hmm...

The first photo looks alright in most parts, but with streaks in the top bit. The 2nd and 3rd/4th (those two are identical photos) look like you sharpened on a poor quality stone, say an aoto dud, or like you didn't spend enough time to do a good job.

I'm assuming the finish was pretty uniform before you took the knife to the Hakka? In other words, this was the Hakka's doing and not something leftover, right? You need a good starting point. Anyway, once you get the slurry up on the Hakka are you gradually lessening your pressure (which should never have been strong on this stone anyway) and allowing the slurry to become finer and erase coarser patterns, while making contact with the uneven bits on the non-flat parts of the blade? With a normal Hakka, you should get a kind of critical mass of pretty smooth slurry that you can sharpen along - kind of a buffer between stone and knife - even without directly touching the hard surface of the stone, and that can last for a little time before it dries and catches a bit and you need to add a few drops of water to continue. When you hit that zone, that's when you get the best finish. If you're doing that, but still have the streaks after then maybe the stone just isn't consistent/clean enough and it's not your fault.

Me, I've tried 3 Hakka which were softer finishers, only 1 of which was from JNS (I'm not sure where you got this one) and so might represent a wider sample. They were all pretty consistent, and so my impression is that they usually are. One, however, was 'grippy' and would tend to leave some streaks unless you have careful control. It was harder than the others, though, and you described yours as very soft.
 
m/file/d/0Bwa1j-dlUS25d3R5dndBLWk3U2xZSDc5cTlWRld0LUdobkRR/edit?usp=sharing[/IMG]
https://drive.google.com/file/d/0Bwa1j-dlUS25clNReGVCeFJPaG9SaU1UMkIyZmllY1JDNVg0/edit?usp=sharing
https://drive.google.com/file/d/0Bwa1j-dlUS25bXZEOFc1Y04tXzBvODVqUVRvZmpadXAxa2Zv/edit?usp=sharing
https://drive.google.com/file/d/0Bwa1j-dlUS25UmVVUkRWVzktalo4cGlyOWRhZEM1b1MwYVUw/edit?usp=sharing
https://drive.google.com/file/d/0Bwa1j-dlUS25UmVVUkRWVzktalo4cGlyOWRhZEM1b1MwYVUw/edit?usp=sharing

ok guys its definitely the stone, it starts out at a 2k grind that very quickly moves to god knows what but its still cutting the hell out of my jigane, no amount of moving slowly, softly, avoiding the inclusions, the stone simply does not agree. There are small particles embedded in the higane, is this normal? I hear of pitting but I know this is not the case im just wondering why this is occurring, because its not it a striated form which would be caused from the grinding the stones, but dimples (hence pitting). Does anybody have any literature on this. Also should i get a 4k or 6k synthetic instead? Ideally i would want to get a Jnat soft enough to polish the jigane.
 
Asteger said:
Scratchy and uneven finish, but looking more uniform in places. Hmm...

The first photo looks alright in most parts, but with streaks in the top bit. The 2nd and 3rd/4th (those two are identical photos) look like you sharpened on a poor quality stone, say an aoto dud, or like you didn't spend enough time to do a good job.

Yes, A cheap polisher I was trying to put a mirror polish on the jigane just to see if I could:/ not my best idea. But my mistake those photos shouldn't have been uploaded. The lines near the shinogi were cause from skidding.

I'm assuming the finish was pretty uniform before you took the knife to the Hakka?

Correct, i even went over the jigane with polishing sandpaper to have a clear base to work from.

In other words, this was the Hakka's doing and not something leftover, right?
Yes

Anyway, once you get the slurry up on the Hakka are you gradually lessening your pressure (which should never have been strong on this stone anyway) and allowing the slurry to become finer and erase coarser patterns, while making contact with the uneven bits on the non-flat parts of the blade?
Yup

With a normal Hakka, you should get a kind of critical mass of pretty smooth slurry that you can sharpen along - kind of a buffer between stone and knife - even without directly touching the hard surface of the stone, and that can last for a little time before it dries and catches a bit and you need to add a few drops of water to continue.
Yup

it's not your fault.
Thanks

My stone is very soft, but to make sure, I preped a slurry with a tomo nagura and went back and tried it with creating a slurry with a clean stone and blade and it still scratched, but it was very smooth to the touch.
Click to expand...
 
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