Sigma Power Ceramic 6k Stone Breakage

[Randy Karst]

Wondering if anyone has insight into this; I have 2 Sigma Power Ceramic 6K stones (1 with a wooden base & 1 without). I grabbed the 6k stone without a base a couple of days ago to do some honing and as I walked into the kitchen from the garage with it, the stone broke in-half in my hand, one half falling to the floor. The stone was dry and had not been bumped or dropped or suffered any known abuse (it is a second hand stone to me). Is this a common issue for this particularly stone? I certainly can see the value of the wooden base on my other 6k stone now. I am thinking of trying to epoxy the stone together, but maybe I need to provide a base for it as well.Regards.Randy

[david charlesworth]

I have used polyurethane glue for stones, many times. Works well. Epoxy should work well too.

When my King 800 stones get thin, two are laminated together. They have then been used right down to the glue line, without problems.

If the stone is thin, I think a base would be good. I have used teak and also considered perspex.

Best wishes,
David

[Derek Cohen]

I have epoxied Pro Shaptons to float glass.



Thick perspex would also work - but it needs to be thick enough not to flex.

Regards from Perth

Derek

[Mike Holbrook]

Good ideas, I have one that broke too, should have fixed it long ago. Wonder where I could find a wood scrap.....Maybe Derek's idea is better to prevent flexing.

[Derek Cohen]

Mike, I meant to add earlier, that a good reason for using glass rather than wood is consideration for when used with water. Wood is going to swell.

Regards from Perth

Derek

[george wilson]

i think it would be better to not try gluing the stone back together,as the glue will forever be part of the honing surface,and may be annoying. i recommend fitting the broken stone tightly together,and epoxying it to a piece of float glass.

typed one handed while eating toast.

[John Kananis]

Do you dry your stones flat? If so, consider turning them on their side to dry - will help expand and contract the stone properly.

EDIT: Sorry, just realized this is a ceramic - no experience with these aside from casual familiarization.

[Patrick Chase]

i think it would be better to not try gluing the stone back together,as the glue will forever be part of the honing surface,and may be annoying. i recommend fitting the broken stone tightly together,and epoxying it to a piece of float glass.

typed one handed while eating toast.

I think this is right. Keep in mind that the Sigma is a porous ceramic stone, so whatever glue you use may diffuse beyond the bond line and create a larger discontinuity than you expect.

I'd be less worried about doing that with a nonporous resinoid stone like a Shapton, both because the stone is a closer match to epoxy (resin either way) to begin with and because it won't migrate.

[david charlesworth]

The polyurethane glue which I have used does not create a noticeable discontinuity in the feel of the sharpening surface.

Epoxy, being that much harder might, but I doubt it.

Best to experiment with a cheap stone!!

David

[Randy Karst]

Thanks all for the ideas on how to best bring the stone into service again. I like the idea of glueing it to a piece of teak (also considering bamboo) or float glass utilizing polyurethane glue. If the joint is tight, everything should be fine. Frustrating to have it happen like it did. I do dry my stones with them laying on their sides to facilitate more even drying. Patrick thanks for the caution regarding the possibility of glue diffusion with this stone, I hadn't considered that.
Regards,
randy

[Patrick Chase]

Thanks all for the ideas on how to best bring the stone into service again. I like the idea of glueing it to a piece of teak (also considering bamboo) or float glass utilizing polyurethane glue. If the joint is tight, everything should be fine. Frustrating to have it happen like it did. I do dry my stones with them laying on their sides to facilitate more even drying. Patrick thanks for the caution regarding the possibility of glue diffusion with this stone, I hadn't considered that.
Regards,
randy

Now that I've had a chance to think about it, the thing you should definitely do is reach out to Stu at toolsfromjapan and see what he recommends. He knows that stone inside out.

[Steve Kang]

Wondering if anyone has insight into this; I have 2 Sigma Power Ceramic 6K stones (1 with a wooden base & 1 without). I grabbed the 6k stone without a base a couple of days ago to do some honing and as I walked into the kitchen from the garage with it, the stone broke in-half in my hand, one half falling to the floor. The stone was dry and had not been bumped or dropped or suffered any known abuse (it is a second hand stone to me). Is this a common issue for this particularly stone? I certainly can see the value of the wooden base on my other 6k stone now. I am thinking of trying to epoxy the stone together, but maybe I need to provide a base for it as well.Regards.Randy

Hi Randy, I also had a sigma 6K that developed cracks. I emailed Stuart at TFJ and it was promptly replaced. Apparently there may have been a bad batch of these or it could have to do with drying technique.

[Tony Shea]

I couldn't recommend Derek's idea of using glass highly enough. When I first purchased Shapton Pro's I decided it was a good idea to try mounting my 1000 grit to a piece of teak. I didn't do the other stones just because I wanted to see how it worked out. For the longest time I actually really liked having mounted to a piece of wood and decided to do the others the same way but never did out of laziness. About halfway through the life of the 1000 I started noticing hairline cracks on this stone. After a while this got a lot worse and has multiple large cracks across the whole surface. But the stone remained usable as I did a decent job of gluing. The other stones never showed any signs of cracking at all. My opinion as to why this one stone developed the cracks is due to the constant movement of the wood under the stone causing a whole lot more movement than it is designed for and ultimately just broke the stone in multiple places. I highly recommend staying away from any kind of wood for mounting your stone on.

I ended up mounting the rest of the stones to 3/8" plate glass and was able to use these stones right down to the epoxy without any trouble at all. I am a Shapton guy and am currently on my second set and all mounted to 3/8" plate glass that I got cut to match the size of the stone. These pieces of glass were actually really cheap as they were small enough to come from scraps the local glass guy had laying around.

IMO using glass is the ONLY way to go.

[Mike King]

So, I just had my second 6k grit sigma power select II stone break on me. They've never been dropped, are stored dry indoors, yet this one developed cracks about a year into it's life. I got three years out of the replacement. Is that what one would consider a reasonable life? Is there a better 6k stone I should replace this one with?

Thanks,
Mike

[David Eisenhauer]

I've had a Sigma II 6K stone (from Stu) for 4? 5? years and no signs of cracking at all. It is not mounted on anything, stored usually on its side, occasionly left soaking overnight or even a day or two before remembering to remove it from its water tub.