Is it possible to verify a CBN grinding wheel is really CBN and not diamond?

[Flynth]

As in the title. I have a so called U3 "universal" tool cutter grinder (a Deckel D0 Chinese clone). Some months ago I bought what was then described as a CBN grinding wheel (no grit number etc). It was bought from some guy selling new-old soviet made things. Previously he was quite reliable. When the wheel came I noticed it had green bonding resin and marking in Russian letters KB. I assumed that KB stands for cubic boron in Russian. It also had markings 100x80 and letters AOC. I assumed that 80 would be grit size and 100 is diameter. There was also some handwriting on wrap paper that had wheel dimensions and "10c". That was first when I became a bit surprised, is cbn measured in carats too?

The wheel had wrong hole size so I didn't use it for few months. However, as of recently I need a tiny boring bar (for a 3mm hole) and I had some 4mm hss rounds on hand so I decided to try my "cbn" wheel. I made an adapter to mount it on my grinder and I noticed it cuts very slowly, but leaves a mirror-like finish as if it was extremely fine grit. When pressed slightly harder it generated quite a bit of heat and didn't cut better. When stopped it looks as it was glazed. I gave it a bit of aluminium oxide stick, but it made no difference.

So I'm now suspecting this is not a CBN, but hard bond diamond with fine grit. I'm considering de-glazing it with a very fine grit sharpening stone as I assume my aluminium oxide didn't work due to big grain size. Then I'll be trying it with a piece of carbide to see if it cuts. Would cbn cut carbide at all?

I'm starting this thread to ask if there is any way to tell cbn from diamond other than by performance. Do they look different under a microscope etc? Perhaps there is some characteristics of one and not the other I can test.

Attached is the wheel photo (with my adapter installed).

 

[Martin W]

I believe the CBM is as hard as the diamond but allows you to cut ferrous metals. CBM will cut carbide.
Cheers
Martin

 

[Flynth]

I believe the CBM is as hard as the diamond but allows you to cut ferrous metals. CBM will cut carbide.
Cheers
Martin

I have tested it and due to it having hard bond material it actually feels a little better or the same when cutting carbide. Attached is a photo of a broken carbide insert I tested it on.

If it is indeed CBN and not mislabelled diamond I would expect it to cut steel much better,but I have no experience with cbn so I don't know. I just heard it is supposed to cut better.

There are some Chinese sellers on aliexpress that have wheels described as cbn, but the same wheels are elsewhere described as "diamond cbn" as if it was the same thing which makes me think they are actually diamond. Perhaps with tiny addition of cbn.

I wish there was a cheap source of cbn wheels for hobbyists somewhere like there is for diamond.

 

[homebrewed]

Chemical methods to tell the two apart would be pretty hard on your wheel. Relatively non-destructive methods would be IR spectroscopy or Raman spectroscopy, both out of the reach of the average hobbyist. A dedicated (perhaps fanatical?) hobbyist could probably make or refurbish something.

Somehow vaporizing a small sample and looking at the visible light spectrum is feasible but not totally non-destructive.

So if you're intent on 100% assurance it's CBN you'd be better off to bite the bullet and just buy from a reputable source.