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View Full Version : Cracks in Sigma 6000 waterstone



Bogdan Ristivojevic
03-21-2018, 12:06 PM
I am using sigma waterstones for 2 years or longer. They are left in water for few days, than dried and stored for long periods. I worked a lot recently, and my stones were in water for 4 weeks. They were not exposed to cold, and from time to time water level lowered and they were not completely submerged. From what Stu posted, Sigma stones can be held in water indefinitely.

Just noticed that pink 6000 developed a crack, covering almost whole 2 sides. Nothing broke off, but crack is clearly visible. It is definitely not manufacturing issue, as I would notice it much earlier.

Is something wrong in keeping Sigma stones in water for long times? I don't see anything on other stones (120, 400.1000.13000) Should I do something to prevent replacement stone from having same issue? I know that there is no cure for the stone, once they fully separate. Only good thing is that crack is parallel with surface, almost on half of stone, and I hope I will be able to make base, and have 2 stones ;)
Anyway, they perform so well that I won't hesitate to buy same type, even if lifespan is 2 years.

Patrick Chase
03-21-2018, 1:13 PM
I had a Sigma Select II 6000 (the solid orange one, not the pink-speckled one that most people have) that cracked in half, but IIRC I had dropped that stone a year or so before, so I think it was a case of latent damage from my mishandling rather than a defect. In any case I clamped the two halves together and glued the whole mess to a varnished wood base, and it works great.

I also have a Sigma Power 6K (the speckled one) and store that in water. I haven't seen any issues.

David Bassett
03-21-2018, 1:24 PM
... and from time to time water level lowered and they were not completely submerged. ...

I can only speculate, but this jumps out at me. I wonder if your problem was caused because the stone started to dry out unevenly?

Bogdan Ristivojevic
03-21-2018, 2:39 PM
That is exactly what I thought, but crack isn't limited just to exposed portion of stone. One of short sides have crack going across, other doesn't, crack is going on long side right to the corner but don't cross to short side. .

Anyway, I added few goodies on Stu website, and I will order replacement tonight. Better to have spare stone, than to be left without one, as it takes time.

Mike Baker 2
03-21-2018, 2:45 PM
That is exactly what I thought, but crack isn't limited just to exposed portion of stone. One of short sides have crack going across, other doesn't, crack is going on long side right to the corner but don't cross to short side. .

Anyway, I added few goodies on Stu website, and I will order replacement tonight. Better to have spare stone, than to be left without one, as it takes time.

What and where is Stu's site?

David Bassett
03-21-2018, 3:08 PM
What and where is Stu's site?

Stu runs Tools from Japan (http://www.toolsfromjapan.com/store/) to source domestic Japanese tools to us overseas. His Sigma Special Set (https://www.toolsfromjapan.com/store/index.php?main_page=product_info&cPath=335_404_403&products_id=1667&zenid=578ae7bdca3406d204a4aa0a17928bc9) is often recommended to woodworkers.

You need to be aware this is a part-time one-man shop and things have always gotten slow when his real life intrudes. He recently lost his Mother and dealing with that seems to have slowed things down even more than usual. So be patient and don't expect Amazon Prime turnaround.

Bogdan Ristivojevic
03-21-2018, 3:30 PM
If you disregard waiting time, I would rate Stu's service as exceptional. His prices are half of European, for the same products. He is slow, but I never heard anyone who hadn't got what he ordered at the end.

Only issue with his shop that it is hard to stop ordering. I planned Suehiro Cerax 320 and Suehiro Kouga 3000 for next order, just for testing, but replacement for sigma was more important.

Rowan Page
03-21-2018, 4:05 PM
Hi I've been using this stone for 7ish years ( since Stu first started carrying them ) as a finisher for kitchen knives and more recently for plane blades and chisels. I've only ever used it 'splash and go' , from memory this is how it was advised to be used, it has never cracked .
This is the " jinzo renge " version with the spots I have.
An excellent stone!

Bogdan Ristivojevic
03-21-2018, 6:03 PM
Same jinzo renge with spots. Ordered another one, and I won't soak this one.
I also sent e-mail to Stu, lets see if he will respond.

Malcolm Schweizer
03-21-2018, 7:21 PM
I do not recommend soaking man-made stones for long periods of time. I know for certain Naniwa says not to, and I know through experience that Nortons will soften if soaked too long- especially the 8000. I personally believe that the crazing that has been a problem with Naniwa Chosera stones is due to uneven drying. I own quite a few of them and not one of them has ever developed cracks. I believe this is because I am VERY careful about standing them on edge in a drying rack to let them dry evenly all over.

I do have some Sigma stones and have not experienced any cracking, but I do the same as above. I would speculate that it's a combination- soaking for long period, and letting it dry unevenly. That's a double-whammy.

Patrick Chase
03-21-2018, 7:49 PM
I do not recommend soaking man-made stones for long periods of time. I know for certain Naniwa says not to, and I know through experience that Nortons will soften if soaked too long- especially the 8000. I personally believe that the crazing that has been a problem with Naniwa Chosera stones is due to uneven drying. I own quite a few of them and not one of them has ever developed cracks. I believe this is because I am VERY careful about standing them on edge in a drying rack to let them dry evenly all over.

I do have some Sigma stones and have not experienced any cracking, but I do the same as above. I would speculate that it's a combination- soaking for long period, and letting it dry unevenly. That's a double-whammy.

You have to know what sort of stone you're dealing with. The Naniwa Pros/Choseras use magnesia binders, and shouldn't be soaked for more than 10 minutes or so. The SuperStones use resin binders and shouldn't be soaked either. Shaptons are similarly limited, as are some Imanishi polishers. As you say the typical failure mode when soaked is cracking or crazing.

The Sigmas all use ceramic binders, and are rated for indefinite soaking.

Mike Baker 2
03-21-2018, 9:09 PM
Stu runs Tools from Japan (http://www.toolsfromjapan.com/store/) to source domestic Japanese tools to us overseas. His Sigma Special Set (https://www.toolsfromjapan.com/store/index.php?main_page=product_info&cPath=335_404_403&products_id=1667&zenid=578ae7bdca3406d204a4aa0a17928bc9) is often recommended to woodworkers.

You need to be aware this is a part-time one-man shop and things have always gotten slow when his real life intrudes. He recently lost his Mother and dealing with that seems to have slowed things down even more than usual. So be patient and don't expect Amazon Prime turnaround.
I'm familiar with the site, did not know Stu ran it. He comes highly recommended, not just here, but in other circles I run in.
And yes, i saw the recent thread, and i have no issues with one man operations.