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8th January 2019, 11:10 AM #16GOLD MEMBER
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I started another thread two days ago regarding CBN v's Diamond and posted a link to Rob Cosman discussing them and his experience with them. He has been using one commercially to do all the tool and blade preparation on the tools he sells and his experience is there has been no drop off in performance or wheel quality. Whether that holds true for all brands is not clear but if they are $500 each they just got crossed off my list of tools for next Christmas, CBN will do me thank you very much. I can't see for sharpening WW tools any difference in performance or longevity. The question that this raises is why did Tormek go down the path of diamond and not CBN, do they know something that current CBN users don't?
CHRIS
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8th January 2019, 11:39 AM #17
Chris, I have had a good report, and a demonstration, from a clubmember on the CBN wheel for the Tormek. Frankly, I think this is a waste of money, since the grinding would be slow, even with a coarser wheel ... which sort of defeats the purpose if you are a turner. The Tormek diamond wheels are much more expensive than the after market CBN wheels, and do the same job. I would trust CBN better, unless you are grinding carbide. The reason that the Tormek can do diamond is very likely the low speed and, hence, low heat. I have my doubts on a bench grinder for anything other than carbide.
Regards from Perth
DerekVisit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.
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8th January 2019, 04:47 PM #18GOLD MEMBER
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Derek, Rob Cosman has been using diamond wheels on a high speed grinder for probably hours a day and extols the fact that it has not changed in sharpening performance which is the usual complaint regarding diamond plates. I have a CBN on a half speed grinder but I am going to change it to a high speed grinder to see how it compares to the slow one. I haven't got a Tormek so the costs of their diamond wheel does not worry me but I take your point of how they can justify it though. Brand loyalty would have to be very high to fork out that much.
CHRIS
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8th January 2019, 07:15 PM #19SENIOR MEMBER
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Tormek must be on the back foot with the availability of CBN (and I suppose diamond) wheels now. I suspect that if they survive it will be due to their jigs rather than their sharpening stations, although they always were more of a high end, low volume but high markup kind of brand.
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18th January 2019, 04:42 PM #20SENIOR MEMBER
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Cosman's grinder is a variable speed one - he may not be running it at full tilt all the time. That said, we woodworkers are the bottom of the food chain, diamond wheels and cBN wheels have been industrially for decades. I would hazard a guess that the knowledge of issues with diamond wheels and steels comes predominantly from industrial applications where the conditions are very different to a home or small workshop.
My understanding of the phase diagram could be incorrect (I'm not a materials engineer Jim!) but I believe carbon begins dissolving in solid iron at 400C+. Considering that plane irons/chisels already have carbon dissolved in them, it may take a higher temperature than that. Since we're trying not to burn the steel as well we would probably have a scenario where very little of the diamond wheel would be dissolving into the steel.
Diamond plates have entirely different problems with the diamond lamination failing or the diamonds fracturing. I can't imagine hand sharpening getting the edge anywhere close to 400C.
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