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 Post subject: Sharpening convex 3V
PostPosted: Tue Jul 02, 2013 2:09 pm 
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Joined: Thu Apr 19, 2012 7:18 pm
Posts: 7773
Location: Madison Wisconsin
Hello Team CHEFKNIVESTOGO,

what is the best way to strop a CONVEX 3V-steel from Barkriverknives? Looks like the stropping with the usual black/green-compound is waste of time for the hard steel.

Is Diamondspray recommended 3V-steel blade ? Respectively which micron gradations are reasonable ? Which strop would be ideal used with diamond spray on a CONVEX blade ?

Please, let me know what item to order from your offers!

I thank you already in advance for a your support.

Best regards!

Albert



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 Post subject: Re: Sharpening convex 3V
PostPosted: Tue Jul 02, 2013 2:31 pm 

Joined: Thu Mar 21, 2013 10:08 pm
Posts: 147
in truth best way to fix them up is on a belt sander with the proper micron belts and leather or felt belts

i ll put some thought into how to do it at home


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 Post subject: Re: Sharpening convex 3V
PostPosted: Tue Jul 02, 2013 3:29 pm 
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Joined: Thu Apr 26, 2012 5:13 pm
Posts: 2925
Location: CT
3V is a very tough steel. Some guys used to strop a knife on sandpaper and a mouse pad for a computer, but I never really had great results with it. I don't think it would work on a tough steel like 3V. Belt sander with belts like Butch said would probably be the best way to go.


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 Post subject: Re: Sharpening convex 3V
PostPosted: Tue Jul 02, 2013 5:49 pm 
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Joined: Tue Oct 23, 2012 1:14 am
Posts: 604
Location: San Ramon Ca.
I use the DLT strops with the BR black and white compound. 3V is is pretty tough but it just takes a bit more time stropping. Sharpness per say depends more on the grind of the knife and what your usage is. A harder backing using w/d sandpaper might be a good choice.



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 Post subject: Re: Sharpening convex 3V
PostPosted: Tue Jul 02, 2013 7:17 pm 

Joined: Tue May 29, 2012 12:29 am
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You don't want to go too fine and you want to use diamond or CBN. Instead of a mouse pad just use a leather strop as a sharpening base with wet/dry sandpaper, it will provide enough "give" to allow for proper convexing and will make the transition to stropping much easier.

I wouldn't go below 1 Micron.


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 Post subject: Re: Sharpening convex 3V
PostPosted: Wed Jul 03, 2013 4:01 am 

Joined: Thu Mar 21, 2013 10:08 pm
Posts: 147
i ll 2nd the CBN or diamond (V carbides are hard)on leather and depending on how much convexing on the blade maybe a towel under the leather to add a bit more give to the strop


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 Post subject: Re: Sharpening convex 3V
PostPosted: Thu Jul 04, 2013 2:50 am 

Joined: Thu Jul 04, 2013 2:33 am
Posts: 6
Looks like it would be vast opinion the diamond or CBN spray is suitable for 3V steel.
On the first line I want a durable, razor-sharp blade, my secondary goal would be a "glossy" edge line, the workflow is still not entirely clear to me:

Which micron degree replaces the whetstone or emery paper :?:
Which "fineness" replaces the usual (black / white / green / red) compound :?:
Should I still strop with a specific compound after the spray application of diamond or CBN :?:

Is there a "(leather?)-strop" which surface texture is ideal for combining diamond spray and a convex blade :?:
CBN or diamond spray - which works better for me :?:


@ Jason B.: You would not go below one micron, why not 0.5, 0.25, or even more finely... :?:



Thanks for your thoughts / Albert


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 Post subject: Re: Sharpening convex 3V
PostPosted: Thu Jul 04, 2013 3:39 am 

Joined: Tue May 29, 2012 12:29 am
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CBN or diamond will both work, because of the vanadium in the 3V one of the two compounds should be used over standard black, white, green compounds.

Why not lower than 1 Micron? Because its not a straight razor and will do nothing but reduce edge retention. Knives used for chopping work better with a polished edge, knives for cutting are best closer to 1k.


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 Post subject: Re: Sharpening convex 3V
PostPosted: Thu Jul 04, 2013 10:57 am 

Joined: Thu Jul 04, 2013 2:33 am
Posts: 6
THANK YOU Jason :D

Your recommendation to bring a dull convex 3V-blade to razor sharpness in summary:
Use a dry / wet sandpaper on a leather strop and exit stropping with diamond or CBN-spray - not below 1 micron. DONE.
I do not need any standard black, white, green compounds.

One question I have left:
Where the ideal transition from sandpaper to the diamond spray, so what sandpaper grit is to use, before I go to the diamond 1 micron :?:


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 Post subject: Re: Sharpening convex 3V
PostPosted: Sun Jul 07, 2013 4:22 am 
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Hope I'm not too late on this thread. I do have the perfect excuse for not getting to it sooner. I was at a Bark River Grind-in :)

And the question of sharpening CPM3V came up. And I had a full range of compounds. And Jim Stewart with a CPM 3v knife in hand :)

We started with a 'factory sharp' edge.

What we found was the following. At around 9 microns (CBN) there was a slight improvement. At 4.5 microns there was a VAST improvement. 2 Microns and people were 'dancing around happy' at the results. Then we kept going - all the way up - 1 micron CBN, 0.25 micron Polycrystalline diamond, 0.1 micron CBN and finally 0.050 poly and 0.025 poly. Converting this to grits 9 microns is ~1500 grit, 4.5 microns ~ 4k, 2 microns 8k, 1 micron 16k, 0.25 microns 64k, 0.1 microns is 160k, 0.050 is 320k and 0.025 microns is 640k.

By the time we hit 0.25 microns, the edges were treetopping arm hair. Beyond that it just became more effortless. Absolutely giddy at 0.1 microns. We quickly ran out of ways to describe the increasing but consistently greater levels of sharpness.

There were a lot of converts in the room. In fact that's all there was of those that tried it on all sorts of Bark River knives, but most especially the CPM 3v, which held an exceptional edge.

For strops we used both the Kangaroo strops and the Nanocloth strops as the substrate or base to put the compounds on. After demonstrating a few simple 'tricks' for doing convex edges on flat surfaces - the strops are mounted using either aluminum for smaller sizes or glass for bench sized strops - people were able to get impressive edge improvements with EASE. After initially loading the strops, no reloading of the strops was done during the grindin (not necessary) after multiple users and knives were done.

So for example, using 9 or 4.5 micron CBN edge improvement was achieved in 15 or so strokes per side. Easy. And further improvements with a similar level of effort.

How sharp do you want to get your knife? Well that's up to you, but clearly increasing levels of refinement, most specifically on CPM3v can be achieved using CBN and Poly diamond preparations that are difficult or impossible to achieve using the standard BR compounds alone. This is certainly not saying that the standard BR compounds are not good as I had the chance to use them in the process of making a couple of knives for myself :)

What I found most interesting is the good response at the coarser CBN grits. I didn't have any 15 micron CBN with me but I suspect I would even get some improvement at this level, not because of the grit size but rather because of the interaction with the vanadium carbides compared to compounds that don't contain abrasives as hard as the vanadium carbides. Clearly the compounds are refining the carbides themselves rather than just relying on carbide fallout. For this reason I would recommend using the 9 or 15 micron CBN as a starting point for doing edge touchups on edges that after use have dulled a bit compared to a factory edge.

---
Ken



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