Community Sharpening Journal

[Deadboxhero]

Thanks for all that, Shawn!

Thank you,

Keep your knives sharp, but your stones sharper.

:D

[Wandering_About]

Thanks for the "Christmas present" of some very interesting info Shawn!

[TkoK83Spy]

*As Barkeepers Friend sells out across the country* haha! Very cool, thanks for that Shawn.

[Deadboxhero]

Right on, Merry Christmas and a Happy New Year 2024.

[Bolster]

Spyderco Brown Ceramic under magnification at 600x...

Excellent curriculum here from Professor BBB, thanks so much for the education. Clipped and saved for future review.

[Deadboxhero]

Spyderco cBN Benchstone

This is the coarser "400 mesh" side

Yet, there is a large amount of 60um cBN grains which would be closer to ~250 Mesh or ~200-300grit depending on what grit scale is used (FEPA, JIS etc)
It should be noted that all sharpening stones will have a range of abrasive sizes and that none have 100% abrasive grains in the exact size.

More detailed reading about grit size and ratings can be read here
https://www.gritomatic.com/pages/grit-fundamentals

Regardless of discrepancies in grit ratings, the size of the cBN we see in the image makes the coarse side cBN Benchstone a highly effective grit size for repair and reprofiling.

While the basic information about cBN can be regurgitated for those that may not know such as cBN being ~4500Hv and diamond being twice as hard at ~9000Hv and the chemical and thermal stability with the grinding steel at high speed with power equipment being superior with cBN when cutting steel there are far more interesting curiosities to share that never see the light of discussion.


What is fascinating about looking at the cBN under magnification is seeing the amber color of the cBN abrasive grains.

Most often cBN may be thought of and seen as "black" "blocky" shaped abrasive grains however interestingly enough, there is a range of colors that cBN is sold in by abrasive manufacturers and suppliers from amber, gold, brown to black.



Even more interesting is that there can be different mechanical properties in toughness, friability, hardness and wear in inverse proportions to each other giving options for selecting the best compromises for a given application.

However, the specific colors are not universal to specific properties such as amber always being harder than black etc since there are multiple ways engineers can create the coloring through manipulating the crystal structure.

Unfortunately, for curious minds every cBN manufacturer has its own proprietary engineering to achieve the different properties and colors of there products and the testing done by these manufacturers is very expensive so it's not publicly shared information not to mention being very esoteric information.

So, the quality in performance and properties can vary more widely between manufacturers even with the same color and shape of cBN.



In conclusion, we often think about the edge stability of the knife steels that we like. Regrettably, there has been little work to find or improve the "edge stability" between the different types of cBN or other abrasives for knife applications since the information is so proprietary and expensive.

Perhaps with continuous work over time there could be a unification between wonderful work that has been done on steels with more work on abrasives with more emphasis on abrasives designed more specifically for knife applications to further enhance the performance, enjoyment and experience the end user can receive.

Yes, the quest for the highest performance never ends but perhaps that's what makes it so enticing to partake in.

Enjoying the journey.

[RustyIron]

the high toughness of AlOx, can also be a downfall because it will not break down and self-sharpen with use. AlOx simply goes to dull which further decreasing cutting performance.

Dude! This post is particularly timely.
Last night I was flattening/restoring some stones, and was pondering my Sharpmaker rods.

I'm no expert on abrasives or ceramics, but I imagine the Sharpmaker rods as being aluminum oxide held together by some kind of magical ceramic spell. It stands to reason that through use, the exposed aluminum oxide on the surface of the rods will become polished, thus degrading performance.

Would it make sense to periodically touch up the surfaces of the Sharpmaker rods with silicon carbide on a glass plate? It seems like a good idea.

[Deadboxhero]

the high toughness of AlOx, can also be a downfall because it will not break down and self-sharpen with use. AlOx simply goes to dull which further decreasing cutting performance.

Dude! This post is particularly timely.
Last night I was flattening/restoring some stones, and was pondering my Sharpmaker rods.

I'm no expert on abrasives or ceramics, but I imagine the Sharpmaker rods as being aluminum oxide held together by some kind of magical ceramic spell. It stands to reason that through use, the exposed aluminum oxide on the surface of the rods will become polished, thus degrading performance.

Would it make sense to periodically touch up the surfaces of the Sharpmaker rods with silicon carbide on a glass plate? It seems like a good idea.

Definitely something that can be explored in more detail to see the differences that different SiC grit sizes can have on performance and wear on the stones.

[Bolster]

Would it make sense to periodically touch up the surfaces of the Sharpmaker rods with silicon carbide on a glass plate? It seems like a good idea.

Same exact question here…!

[RustyIron]

Definitely something that can be explored in more detail to see the differences that different SiC grit sizes can have on performance and wear on the stones.

Well as long as you're not telling me it's a dumb idea, I'll put it on my list of things to try out. Or maybe I'll try it out on some other ceramic rods that aren't part of my beloved Sharpmaker. Thx.

[pinchyfisher]

There are threads regarding lapping the ceramic benchstones for flatness that would be relevant to this conversation- I just can't find them right now.

I believe the conclusion from the likes of Sal and Cliff Stamp is that the ceramic stone will to some extent take on the aggressiveness (or lack of) of the lapping compound used.

I can attest that lapping the medium and fine ceramic benchstones with very course SiC really increased their aggression for a time.

I believe Cliff had used this property to turn a fine stone into a sort of combo stone (one side factory, one side lapped).

So conclusion- seems legit/worth exploring further.

[Deadboxhero]

Finished grinding and sharpening more CATRA blades for Dr Larrin, also some metallography. Looking forward to seeing his article about it.

[RustyIron]

I believe the conclusion from the likes of Sal and Cliff Stamp is that the ceramic stone will to some extent take on the aggressiveness (or lack of) of the lapping compound used.

Thanks! Both those blokes know a thing or two about knives and stuff. I think I'll try it out on a couple round ceramic rods that I just use for unimportant tasks.

[RustyIron]

Finished grinding and sharpening more CATRA blades for Dr Larrin, also some metallography. Looking forward to seeing his article about it.

There you go again being a bad influence. You should know by now that most of us are weak and lack the discipline to resist fancy new toys.

How about telling us a little about that Andonstar contraption sitting on your desk? My own USB microscope is great for the forty bucks I paid, but really, it's a kiddy toy. Your pictures are great, and I just assumed you had a 'scope that you heisted from NASA. I just googled on "Andonstar," and discovered that they make models that can be had for little more than pocket change.

Being a cheapskate, part of me wants to just order up the cheapest one available. But I'm also an undisciplined child, and want to order the biggest one I can find. Since you have some experience and have already figured it out, what model should I get?

Thanks!

[Deadboxhero]

Finished grinding and sharpening more CATRA blades for Dr Larrin, also some metallography. Looking forward to seeing his article about it.

There you go again being a bad influence. You should know by now that most of us are weak and lack the discipline to resist fancy new toys.

How about telling us a little about that Andonstar contraption sitting on your desk? My own USB microscope is great for the forty bucks I paid, but really, it's a kiddy toy. Your pictures are great, and I just assumed you had a 'scope that you heisted from NASA. I just googled on "Andonstar," and discovered that they make models that can be had for little more than pocket change.

Being a cheapskate, part of me wants to just order up the cheapest one available. But I'm also an undisciplined child, and want to order the biggest one I can find. Since you have some experience and have already figured it out, what model should I get?

Thanks!

It is a nice "USB microscope" it is designed for soldering. It's not quite as good as a real microscope though.

In order to get the pictures like I have been sharing here there is no avoiding or getting around simply just using a legitimate microscope.

Yet, I found the Andonstar is significantly better than a cheaper USB microscope; the images will have less noise. Unfortunately, it also costs six times more.

I use mine for quick inspection and traveling to knife shows since a big microscope is not very portable.

[pinchyfisher]

I believe the conclusion from the likes of Sal and Cliff Stamp is that the ceramic stone will to some extent take on the aggressiveness (or lack of) of the lapping compound used.

Thanks! Both those blokes know a thing or two about knives and stuff. I think I'll try it out on a couple round ceramic rods that I just use for unimportant tasks.

For sure. One thing to note- I used 60 grit loose SiC and the ceramic broke the SiC down pretty rapidly to a fine size. Depending how far you go with lapping you may need to replace/refresh your SiC. I imagine if you don't it'll end up being counterproductive. Keep us posted!

[Deadboxhero]

Spyderco CPM 20cv Manix 2 lightweight factory edge 1000x magnification.

Factory edge has carbides exposed from matrix at the apex. We can see the edge is bristling with carbides from ~2 to 5 micron. On paper the carbide volume should be near ~20% volume which is more than MagnaCut (8%) but less than 15V (23%) but more than 10V (17%) However, CPM 20CV has softer carbides making up the majority of its carbide type.

The carbide type and volume play one of the largest roles in the slicing edge retention after geometry.

Maybe exposed carbides reduce edge stability but increase edge aggression. That would be interesting to test in the future.

[RustyIron]

Very interesting picture.
And thanks for saving my cash. I'm not going to buy another USB microscope. I just need to find a used conventional scope for cheap.

[Guts]

Touched up my Maxamet PM2 on the Spyderco CBN bench stone. Haven't really used this bench stone much as I find it a little too aggressive for my taste, so I only used the 800 mesh side. Then I hit it with a few strokes of 4 micron->1 micron stroppy stuff on leather. Shaves hair and slices paper towel easily so I'm happy. Hope Spyderco expands their line of CBN bench stones in the future, would love to see some higher grit versions.





Don't have as nice a microscope as BBB , but this gets the job done for me. I just use it to look for any microscopic burr I might have missed and it works well in that role.

[vivi]

I suck at close-up photos compared to you guys.

Dropped the edge of my 4 Max Scout by another degree or two. Trying to find the right balance between cutting ability and durability for a folding knife that can be used for chopping.








Pretty standard edge for me. Formed the edge on a 200 grit diamond plate. Polished it on a 300 grit plate. Refined the edge with alternating strokes until it cleanly shaved and I couldn't detect a burr by hand, then hit it once per side with a feather light edge leading stroke on freshly cleaned fine sharpmaker rods.

This is my first AUS10 knife and I like how it sharpens. Not as burr prone as AUS8 and feels a bit harder, but still easy to shape and grind. Not terribly different feeling on the stones than Spydercos 8Cr, just feels a touch more wear resistant / slower to grind. AUS8 always burred hard for me so glad this steel doesn't.