What Stones for Sharpening?

pcmunson

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I'll be interested to see what stones/technique you prefer for sharpening your CPK. I expect to receive my first CPK soon, so your information will be appreciated.
 

Blues

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They can be sharpened or touched up on anything from aluminum oxide through diamonds...freehand or with the use of gadgets (Sharpmaker, guided systems etc.)

Which is best really just depends on your preferences, ability and skill.

I tend to do most sharpening freehand...but oftentimes finish with a few licks on a Sharpmaker at 20* either to clean up my edge of any remaining burr, or to establish a microbevel. Also, a good way to keep things sharp when they don't need a full sharpening.

I prefer diamond hones, (both bonded and plated), and ceramics, (Spyderco bench stones and Shapton Glass) for the most part...as opposed to my Norton oil stones (SiC and AlOx).
 

Blues

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Another added plus of the diamond stone options is that they'll cut ANY of the supersteels, as well as the even harder carbides. Honing with an Arkansas stone can be a chore/PITA with some of the supersteels.
I wouldn't bother to use Arkansas with anything but simple steels like 1095 and such. I still have a few laying around...but they rarely see use.
 
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I just use the Shapton Kuromaku 1000 grit for everything. As long as your edge doesn't have significant damage, it does a really great job and seems to last longer compared to my King stones. I don't go for a mirror polish as I prefer it slightly toothier than not.
 

never.truly.lost

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Freehand with a Fallkniven DC4 is all I have used. A strop to clean up the burr but most of the time just hone the edge with the ceramic side.

Not really that interesting of a system but after 2.5 years with the MC smashing through tens of thousands of cuts, it still shaves arm hair without a hitch.
 
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When it comes to CPK knives the best is no stone! My CPK behemother is the only knife that I did not feel the urge to sharpen straight out of the box and this is a large chopper! When I buy a knife from a maker or company I sharpen it straight out of the box if I think I can do a better job. And until now, I did not have a single knife that I did not sharpen straight away.

Anyway, if I leave the praise aside, I would use diamond or CBN stones for delta 3V. My understanding is there is a small amount of chromium carbide in industry-standard heat-treated 3V and Nathan says that his heat treatment leaves more chromium in the steel matrix (hence the boost in corrosion resistance aspect), which in my opinion means that in delta 3V there are even fewer chromium carbides. I did some controlled experiments in the past where I have sharpened various high vanadium (e.g. S90V), low niobium (e.g. Niolox) and mixed carbide (e.g. CPM-154) steels using Naniwa Chosera stones and resing CBN stones. The consistent outcome was when those steels are sharpened with CBN stones the edge comes out much sharper relative to the choseras. But it does not mean the edge is not good when sharpened with chosera it comes out very sharp but not as sharp and not as sticky/aggresive.
 

Nathan the Machinist

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Yeah, it ain't the chromium carbides in 3V I would be worried about, it's those vanadium carbides, they're a real bear.

I'm talking off the top of my head here, but if I remember correctly 3V is more than 10% carbide by volume. That definitely has an effect on the abrasives..
 

Blues

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Yeah, it ain't the chromium carbides in 3V I would be worried about, it's those vanadium carbides, they're a real bear.

I'm talking off the top of my head here, but if I remember correctly 3V is more than 10% carbide by volume. That definitely has an effect on the abrasives..
Nominal Composition
Carbon 0.80%
Chromium 7.50%
Vanadium 2.75%
Molybdenum 1.30%

(From Crucible)
 

Nathan the Machinist

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Nominal Composition
Carbon 0.80%
Chromium 7.50%
Vanadium 2.75%
Molybdenum 1.30%

(From Crucible)

Nominal composition is not carbide volume fraction. That table is composition by weight. Carbon doesn't weigh much. For example a 1% carbon steel is way more than 1% carbon
 
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Nathan the Machinist Nathan the Machinist Yes, I use my Naniwas Choseras (Chromium abrasive ) for any steel that does not have enough vanadium, tungsten and niobium in it to form a carbide. For the rest of the steels with those harder carbides, no matter the carbide volume fraction I use CBN/Diamond. For some reason, the edge of those steels comes out noticeably sharper with CBN/Diamond. I know some respectable sites and people says carbide tear-out is a myth, but maybe that is the reason for edge coming out more aggressive and sharp when CBN/Diamond is used. They simply cut the carbide at the apex rather than removing it...

I also talking off the top of my head but I believe that the carbide volume of CPM3V is between 5 - 10 %. I will check this out. While we are on the subject, I was wondering if you ever considered using CPM1V for your large choppers which does not require much abrasive edge retention property?
 

Nathan the Machinist

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Nathan the Machinist Nathan the Machinist I just looked up carbide volume from Larin's website. It is stated that the carbide volume is 5.1 % in 3V.

Correcting my previous post, it is also stated that all the carbides in it is already vanadium carbides. I thought a small portion of it is chromium carbides. It seems this is not the case.

:thumbsup:
 
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