What the problem with sigma 3000 3K ???!!

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milangravier

milangravier

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Hello everybody,
I just bought a sigma 3000 and test it today. I think there is a problem with the stone! Because it feels really coarser than 3K. Compared with cerax 3000 it is huge difference. It looks so coarse, I think I could compare it with King 800... It feels even coarser than king 800 I think...!
Here is a video where I compare the 3 stones :
Here is also 3 pictures of the finish I get. OK cerax is not that great too because I did it quick but it looks defenitly finer.

I will contact finetools (that sold me the stone) but do you think there is a problem ? Is there anybody who got the same stone to give me his point of view ? Because this is the 3K stone with the most bite I have ever use !!
 

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hi, yes I lap the stone.
Actually, out of the box it was very different, no kasumi at all, all bright.
Then I lap it very slightly with atoma 600, and got that... I try both sides
 
i dont think its a problem with it. it probably works as intended. but it seems to give a very coarse result for a 3k. more like a 1k.

it probably has to do what type of binder they use, and so on.
 
If only someone had already mentioned this to you...

Anyhow, it's meant for hardened HSS. Use it for what it's meant for, and the scratches will be finer and shallower.
 
Thanks a lot for those feedbacks. Ok, I understand I am using this stone on soft steel clad, so yeah maybe it is one of the cause. But, stropping on C130 (1.3% carbon steel (not hss), it feels coarser like 800 grit.
In this video, from 7:15, the guy is using Sigma 3K and it doesn't feel like in my video :

But I am ok to admit this is not the good stone to use on a simple carbone san mai.
 
The problem I see are the single strong scratches. Do you feel some very coarse particles while working the bevel? Clean the stone and inspect it - do you find little ‘holes’ in it? I have experienced once that the stone would release here and there a few very coarse (like 0.1mm or even larger) particles and these would then cause deep scratches.
 
Matus said:
The problem I see are the single strong scratches. Do you feel some very coarse particles while working the bevel? Clean the stone and inspect it - do you find little ‘holes’ in it? I have experienced once that the stone would release here and there a few very coarse (like 0.1mm or even larger) particles and these would then cause deep scratches.
Click to expand...
I can experience what you say on Cerax 3000, if I use it with not enough caution it releases particles and will scratches heavily.
But on the sigma, no, it doesn't feel that some coarse particles are release, it just feel the entire grit is coarser than 3K. Really more a 800 grit
 
That blade is hardened 20CV with almost 2% carbon & 4% vanadium, not to mention a bunch of Cr.

Which accounts for a whole lot of difference in how the stone will behave, compared to soft cladding.
 
Interesting I had the EXACT same experience with the Morihei green 3k stone. Produced scratches similar to a gesshin 400 and was almost impossible to produce a clean edge with it. Extremely strange feeling stone. it produced a very consistent finish, just no where near 3k
 
Knife2meatu said:
That blade is hardened 20CV with almost 2% carbon & 4% vanadium, not to mention a bunch of Cr.

Which accounts for a whole lot of difference in how the stone will behave, compared to soft cladding.
Click to expand...
I really understand and agree with you point. I am surprised because I have tested a lot of stones and this is the first time I feel this behaviour.
 
Sounds pretty coarse for a 3k. I’m guessing that’s because of what was said above. I’ve never tried the sigma 3k myself but I would guess that’s not really what you’re looking for Milan. Are these scratches more coarse than what you get from your bester 2k?
 
Robert Lavacca said:
Sounds pretty coarse for a 3k. I’m guessing that’s because of what was said above. I’ve never tried the sigma 3k myself but I would guess that’s not really what you’re looking for Milan. Are these scratches more coarse than what you get from your bester 2k?
Click to expand...
far far more. Bester is a razor finisher next to it
 
Alder26 said:
Interesting I had the EXACT same experience with the Morihei green 3k stone. Produced scratches similar to a gesshin 400 and was almost impossible to produce a clean edge with it. Extremely strange feeling stone. it produced a very consistent finish, just no where near 3k
Click to expand...
This is what I get too. I can understand the stone is made for HSS but.. that's very far from 3K on a 1.3% carbon steel...
 
Matus said:
The problem I see are the single strong scratches. Do you feel some very coarse particles while working the bevel? Clean the stone and inspect it - do you find little ‘holes’ in it? I have experienced once that the stone would release here and there a few very coarse (like 0.1mm or even larger) particles and these would then cause deep scratches.
Click to expand...
Did you ever find a solution to this? I have this problem with my king 4k, and to a lesser extent my kitayama 8000. Would love to know if there is a way to get around this.
 
jwthaparc said:
Double post.
Click to expand...
The single bright scratches are bigger particles that will appears clearly on clad. I got that with cerax 3000, naniwa pro 3000, and others. The way to avoid those is having a clean bevel without low/high spot, clean the stone and edge of the stone, work with mud (from nagura or atoma 400/600). As soons as you can heard a weird sound, look at the blade, clean the stone and blade if there is scratches, start over.
Same with naturals when you want the final finish.
 
jwthaparc said:
Did you ever find a solution to this? I have this problem with my king 4k, and to a lesser extent my kitayama 8000. Would love to know if there is a way to get around this.
Click to expand...

I did not. I would guess that it is a fluctuation in the production process.

It seems that these are little clumps of the stone grains that for some reason are bound together more strongly. When you then work on a sanmai bevel, these get pulled out if the stone surface and cause scratches. They usually turn black from the steel, so you can see them as black dots. At first I thought that I am looking at pieces of kurouchi at first. I have also used the stone for razor and got considerable chips in the edge - and when I put it under microscope - at one place I actually found such a clamp wedged into the cutting edge.
 
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Since my stone is quite old, except from the behaviour itself, I can't really say much. It's very difficult to comment over such different experience without the actual stone.
 
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Knife2meatu made a good point saying the stone is made for HSS steels. I think that's the issue.
Thinking about it I got quite some stones that feel different from the grit I expect : for exemple my Nano hone 1K feel much finer and behave much finer than my king hyper 1K. Rika 5K feels coarser than a shapton glass 3K, etc...
For sure each brands made their stone in a certain way and aim, it is somewhat normal to feel big differences between stones.

Actually I try using the Sigma 3K as a 1K, I mean using it just after a 400 gesshin for exemple and it works, it can erase the 400 grits scratches. But the result I got on my san mai will be close to 1k or 2k at best, and will need a 3k or 4k to erase the sigma scratches before going to my naturals. I try some stones for sharpening today (135cr3 and C130 steels) and try Sigma as a 1K, it doesn't feel very nice to me, it feel somewhat very coarse and not in a consistent grit. To me, it's just not a really great stone for what I have to do. But maybe that's a good stone for HSS or high ally steels. I just may try to sell it, so it would work for someone.
 
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Yep. And, oh! I did a little discovery. As I break few weeks ago my naniwa pro 3k (and even I succeed to glue it back together), I bought a new naniwa pro 3K with the sigma, because yeah I thought even if I don't like the stickyness I can live with that and this stone is working great when it's not too much stickying. And... I try the new one just to see, and actually it is different from the other one, far better feel and no stickyness ! Weird, no ? But yes there is differences and I get two naniwa pro 3K that behave differently. I did not make a long polishing with it so maybe it's just the first mm if the stone that is better but... for now it is better.
 
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it might be the binder that have leached out of the old one. its magnesia.
i really like the 2k naniwa pro. feels ultra nice and you get a consistent finish with no scratches. and its cheaper than the 3k.
 
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I really wish the 3k chosera wasn’t so sticky. I guess I should revisit it for bevels. It used to drive me insane. Love the 800 though. One of my favorite stones. I actually noticed a small crack in my 3k the other day. Haven’t used it in a while. I should probably coat it lightly. Looks like it’s on the bottom ish anyways.
 
I really like the Sigma 3k for that one and done, on the fly touch-ups at work. It cuts, yet gives and acceptable finish, and is super quick. It's listed as a Splash and Go, but I prefer to soak it a bit. I also work up a thick slurry first. It does have a sandy-gritty feel, and if you're moving from clay like stones, it is bizarre. I actual replaced a Naniwa 3k with it. I hated that stone. Gunked up quicker than anything else I've ever used. Naniwas give a much finer finish than most, though.
 
I've had a 1k and 5k Naniwa for many years, and have had zero issues with cracking. I really like the finish off the 5k. It isn't the best feeling stone in the range, but the edge is bighty and fine at the same time.
 
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