abrasive effectiveness on varying steels?

hardheart · May 10, 2008

Has anyone made measured observations on different abrasives losing effectiveness on different steels? Like, how hard or how much carbide can a steel have before arkansas stones or chromium oxide strops quit working efficiently? Also, are there steels without enough wear resistance or hardness to sharpen effectively with coarse grades, or diamond in particular?

I've seen these things mentioned often, but with casual observation. Could there be a more structured presentation of expected performance? Polishing/lapping compounds are listed as being suited for precious metals, mild steel, stainless, tool steel; do we have something cutlery specific for aluminum oxide, silicon carbide, ceramic, natural/manmade waterstones, novaculite, cbn, etc?

mete · May 10, 2008

Diamond will cut anything ! There are many variables and certainly all carbides are not equal. For example the HRc hardness [extrapolated] of Chromium carbide is 72 while vanadium carbide is 85 !! That becomes fairly obvious when sharpening S30V compared to even a 154CM. But the use of ceramic and more so diamond solves that problem.

thombrogan · May 10, 2008

That's true. I think hardheart's looking for other factors, too. For instance, boron carbide is softer than diamond, but seems to cut faster when both are in the 0.5-1μ range. Maybe for steels which benefit more from SiC's higher hardness and friability than those which come to life with aluminum oxide or novaculite?

Frank Hillary · May 10, 2008

mete said:
Diamond will cut anything ! There are many variables and certainly all carbides are not equal. For example the HRc hardness [extrapolated] of Chromium carbide is 72 while vanadium carbide is 85 !! That becomes fairly obvious when sharpening S30V compared to even a 154CM. But the use of ceramic and more so diamond solves that problem.

Mete

How hard is ceramic stone? and India stones?

Thanks
Frank

mete · May 11, 2008

That I don't know. Most of my knife sharpening is done with a diamond rod ! When I used to do woodworking especially fine carving I used hard arkansaw and later ceramic. While HRc is used for metals and carbides natural stones have been classed by MOHS hardness.

Lucky Bob · May 11, 2008

Well, commentary on units when it comes to hardness:

1) Mohs is all relative, it's just whether it can scratch or be scratched by the ten defined values (http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness). As such, it's impossible/useless to convert to/from the Mohs scale to a unitful/quantitative scale, such as Rockwell.

2) Unfortunately, you can't measure things like ceramics with the Rockwell tester, and thus it's hard to quantify them using the Rockwell scale. The problem lies with the fact that if a ceramic (or a glass, or most minerals, I would expect) gives way (and Rockwell measures how much something gives way under a given force), it catastrophically fails and breaks, instead of just having a divot in it. That being said, assuming the material in question is uniform/isomorphic, it should be possible to simply vary the applied force until it does fail, and use that as a comparison... that being said, you're still measuring two different kinds of things.

Broos · May 11, 2008

I think the best thing would be to discuss anecdotal experience and compile to achieve a rating of the different abrasives on different steels (at different hardnesses). Even that would be daunting, let alone a scientific basis that I think would be best based on a wear resistance type of testing.

There are other factors that could be just as or more important than just the abrasive - density of abrasive, pressure used, substrate for the abrasive, etc. I think you'd have to categorize the same abrasive depending on how it is presented to the steel - for example a DMT cuts at a "10", same size diamond on cast iron lapping plate cuts at a "6", and a 3M at "8".

Frank Hillary · May 12, 2008

mete said:
That I don't know. Most of my knife sharpening is done with a diamond rod ! When I used to do woodworking especially fine carving I used hard arkansaw and later ceramic. While HRc is used for metals and carbides natural stones have been classed by MOHS hardness.

Mete

Thank you. I just want to know if ceramic is hard enough to polish very hard carbide. Maybe? Maybe not?

Regards
Frank