Where is the Urban Coyote?

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Cambertree
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Re: Where is the Urban Coyote?

#181

Post by Cambertree »

TkoK83Spy wrote:
Sun Sep 15, 2019 6:29 am
I like mine a lot, but after a day of use at work it always needs some loving for that hair popping sharpness I won't leave the house without :)

The grind angles on each side of the knife are quite different so I don't even use the Sharpmaker when touching up. I free hand with the rods, which works..but takes longer than I like.

This is supposedly a tough steel, but I'm thinking of reprofiling to 15dps using the CBN rods in the Sharpmaker. I did it with an M390 Para 3 a couple months ago and took me around 4 hours total. Do you think this knife would be more of the same, in that ball park?
It should be a lot quicker than both M390 and S30V to reprofile the edge area - they both have 3-4% Vanadium - AEB-L has none.

It’s a low carbide, relatively low wear resistance steel.

It is probably run slightly harder than M390 and almost certainly harder than S30V, but the HRC number is the matrix hardness, not the carbides.

It shines in thin, refined edges. Larrin says in his Nitrogen Steels article that it is the toughest knife steel he has tested.
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Doc Dan
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Re: Where is the Urban Coyote?

#182

Post by Doc Dan »

There should be little trouble with reprofiling AEB-L. This is no super steel. It is tough, very tough, but mild mannered and easy to sharpen.
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TkoK83Spy
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Re: Where is the Urban Coyote?

#183

Post by TkoK83Spy »

Awesome!! For some reason I was under the impression that reprofiling with just the CBN rods and a Sharpmaker might be a bit of a bear. Very refreshing to hear otherwise!! I'll get to it some day this week.
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jpm2
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Re: Where is the Urban Coyote?

#184

Post by jpm2 »

Cambertree wrote:
Sun Sep 15, 2019 8:08 am
It is probably run slightly harder than M390 and almost certainly harder than S30V, but the HRC number is the matrix hardness, not the carbides.
I often wonder about this and can't help to think carbide has some effect on hardness testing, with more carbide content (and possibly harder carbides), more effect.
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Cambertree
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Re: Where is the Urban Coyote?

#185

Post by Cambertree »

jpm2 wrote:
Sun Sep 15, 2019 12:32 pm
I often wonder about this and can't help to think carbide has some effect on hardness testing, with more carbide content (and possibly harder carbides), more effect.
Yep, logic would seem to suggest that carbides must have some influence on the depth of the indentation.

I’ve wondered about this myself.

I have seen micrographs where the test indentation specifically targets areas of ferrite or pearlite banding to avoid carbide readings, but I may be confusing the HRC test with the microhardness Knoop test.

Let me check that when I have more time this afternoon and get back to you on that one.

Or maybe someone can chime in and correct me if I have been in error.
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Cambertree
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Re: Where is the Urban Coyote?

#186

Post by Cambertree »

jpm2 wrote:
Sun Sep 15, 2019 12:32 pm
I often wonder about this and can't help to think carbide has some effect on hardness testing...
Jpm2, it appears you’re right in regard to the Rockwell C test.

I checked a few references and as far as I can tell, the conical diamond indenter just presses down on a random spot (in terms of the microstructure underneath it). Depending on the steel, it seems that carbides would indeed have an influence, in some cases the point might even come down in the middle of a carbide aggregate cluster.

I suppose that’s one of the reasons for multiple readings being taken and averaged. And also for the + or - 1 accuracy level.

I’d confused some photos I saw a few years ago in John Verhoeven’s Metallurgy for the Non-Metallurgist. Those photos were of the Knoop microhardness test, which uses a microscope to aim the indenter at a prepared steel surface, so it only hits a particular part of the microstructure. It also uses a variable load, so the indentation is no larger than the chosen part of the steel it aims to measure.

Here’s a couple of photos from Verhoeven, showing it measuring pearlite and ferrite bands without being influenced by the surrounding structures:
Image
Image

The test apparently uses both the diamond shaped Vickers indenter, and a special elongated Knoop indenter, which is shown in the second micrograph.

Thanks for prompting me to go back and correct my understanding on this.
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