Abrasives in Micron Scale

Clay Allison, I note that you have seen my chart. I hope you like it. 🙂 I used the values from your chart for the Chosera stones. Could you tell me more about these numbers? While neither 5000 nor 10000 is part of the JIS standard these two Chosera values do not match an extrapolation from JIS 1998. If the values were provided to you was their nature further specified or merely “micron?”

Yes, I did read your blog post. It’s the best treatment of the issue I have yet seen; well done.

I decided early in the process that my chart would not attempt to make absolute comparisons if abrasive performance. This is clearly explained in the README.

1. As you well know diamond compound on leather cuts much more slowly and produces a much higher surface finish than the same diamonds on a metal plate. This means that even if the abrasive and the work piece are identical results can be very different.
2. If the type of abrasive is different the results with further diverge; a soft but sharp abrasive may work very fast on soft metal yet be ineffective on high hardness steel.
3. Abrasive roughness (sharpness) plays a large role in performance that particle size distributions do not quantify.
4. The shape (aspect ratio) of abrasive particles is not well addressed in the standards, yet again can have a large impact on performance.
5. Even for a specific abrasive material of a specific particle shape and roughness and a specific median particle size by weight (D50) performance may be different. This is because a single number cannot describe the entire distribution including maximum particle size etc. An abrasive may be more tightly graded than a given standard and yet still comply with it.

So where does that leave us? In my opinion there is still value in a chart like this or I wouldn’t have spent so long putting it together. However I think that is is more useful for considering spacing within a family of products than absolute comparison between them.

Generally I have avoided inclusion of abrasive products that have to be quantified by approximate performance rather than actual PSD values. There are only a couple of exceptions, one of them being the Wicked Edge ceramic rods. I included them partly because a rough micron grade had already been assigned to them (on Clay Allison’s chart) and partly because they were part of a series. If their relative performance to each other, and to a limited degree their performance relative to the WEPS stock plates, can be reasonably approximated then I think their inclusion will be of service to WEPS users.

I am open to other ideas for how this chart may be further developed but I hope the concerns outlined above sufficiently explain my current position on the matter.

Tom, I’m glad you like it, and thank you. Please make sure to look at the linked README file. I gave specific acknowledgement to Komitadjie as his chart was the primary inspiration for mine. With the v0.81 update the README mentions these factors of abrasive performance, among others:

– backing or bonding characteristics
– cutting point density (open vs. closed coat, binder proportion etc.)
– workpiece composition and hardness
– pressure and speed of application (affecting grit penetration depth)

I appreciate the pragmatic note regarding Shapton vs Chosera 5K performance, but as explained I will not be modifying item placement in my chart based on that kind of observation unless it amounts to overwhelming evidence that the datum is false.

I would love to see a chart comparing the absolute performance of many different abrasive products but such an endeavor would be far beyond my budget, if nothing else. I have given it thought however. My best idea is creating several standard steel samples, cutting them into pieces, and sending them to the four corners of the sharpening world. Contributors would then perform specific operations under instrumentation (spring scale, chronometer, etc.) and mail the samples to a lab for surface roughness measurements. Somewhere in the process the samples would need to be weighed on a calibrated lab balance to measure total metal removed. This is probably far too involved and costly to be worth it to most people.