CBN grinding wheels and the steels they are suitable for?

[Frederick Skelly]

Good evening folks,
I usually inhabit the Neander Forum, but I have a hunch you folks will know more about CBN wheels. Would you mind answering a question?

I picked up a copy of the latest Wood Magazine for the article on Grinder Wheels. Wood says that CBN wheels "should only be used for hard steel alloys and carbide tools; carbon steel will damage the abrasive." (I use my CBN for O1 and A2 plane irons and chisels. It works well.)
* Is carbon steel harder or softer than A2?
* Why does carbon steel damage a CBN wheel?
* What kind of tools are typically made from carbon steel?

I realize how ignorant all of this must sound, but I don't know, and I'd like to understand what the magazine is saying. Would someone please explain it to me?

Thanks very much!
Fred

[Allan Ferguson]

Suggest contacting D-Way Tools for authoritative info.

[Reed Gray]

Fred,
Well, if I had known they were doing an article, I would have contacted them. My long version:

http://www.robohippy.net/featured-article/

Short version, CBN is made for grinding hardened steel. This would include just about all plane irons and bench chisels, axe heads, any high speed steel. You can take down carbide with it but it is very slow, and diamond is far better for that.

So, soft metals like the old kitchen knives, old carving chisels, and old turning tools are made from high carbon steel (no idea exactly what that is, but not in common use now days), cold rolled steel, hot rolled steel, along with brass, aluminum, and copper, will clog or load up the wheel. It is not impossible to clean up the wheel. For turners, most of the time if we do it, we just take a heavy HSS scraper and sharpen it as normal. It may take a time or two to clean it up to pretty much 'good as new'. I have been experimenting with the Trend Lapping fluid (there is a long thread here about that) for keeping the wheels clean, and cleaning them up if they get loaded up with soft metal, and it seems to work much quicker than just sharpening a scraper. I need to do a 'before', load up, clean up, and then 'after' shot session just to see what it does.

You are the first one that I know of, today anyway, to ask this question... Good questions really!

robo hippy

[John K Jordan]

I picked up a copy of the latest Wood Magazine for the article on Grinder Wheels. Wood says that CBN wheels "should only be used for hard steel alloys and carbide tools; carbon steel will damage the abrasive." (I use my CBN for O1 and A2 plane irons and chisels. It works well.)
* Is carbon steel harder or softer than A2?
* Why does carbon steel damage a CBN wheel?
* What kind of tools are typically made from carbon steel?

Fred,

I have read a lot of things by a lot of people. Many people just relay what they read somewhere and never actually try what they assert as Truth.

Have you seen the CBN article by Reed Grey (Robo Hippy)? He has tested these wheels extensively and continues to.

I grind many types of tools on my CBN wheels. I have them from 80 grit to 600 grit. Apparently, grinding any hardened steel is fine. Grinding mild steel will load up the wheel but Reed says any loading (metal sticking to the wheel) can be removed by grinding something made from hardened steel. I have ground some non-hardened steel on mine with no ill effects but I do this sparingly. (I have other grinders for that in my weld/metal shop.)

Reed also likes to use this stuff on his CBN wheels: https://www.amazon.com/gp/product/B004NPIMU8
You can send him an email with specific questions - he is a very helpful guy.

Carbon steel can be many things. How much carbon? Hardened to what? According to a book I have by metalworking wizard Tubal Cain (mrpete22 on youtube, Lyle Peterson in life) hardened high-carbon steel is harder and can be made sharper than HSS.

I have never tried grinding carbide with CBN. I use diamond for that.

JKJ

[Frederick Skelly]

Allan, thanks for the reference. I didn't think to contact a manufacturer. Should have.

John, thanks for sharing your experience using these wheels and for the links. "Carbon steel can be many things." Yeah, that's what threw me - made me think I was missing something. Glad to know it was vague to someone more knowledgeable like you, too. Tubal Cain - I've viewed some of his stuff. That guy really is a wizard!

Reed, when I visited your site, I got a serious case of deja vu - I'd come across it while researching CBN wheels months ago. Your site was so helpful that it convinced me to go buy one. I'm glad I did. So let me just say thank you "in person" for all of the help there too! It's a great site and I'll bookmark it this time so I have the reference permanently. I'll spend some time later today re-reading it for things I missed (or that you've added) since last time around.

Once again, thanks for teaching me guys!
Best regards,
Fred