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Switching from diamond plates to stones

Sun Dec 08, 2013 1:53 pm

Hey Mark, I've ordered several things from you and would like to ask a question. I have the DMT DuoSharp Plus 8" (fine/coarse) and the DMT Aligner. I'm working on learning to free-hand sharpen once I can hold a proper angle w/o the guide. Anyway, I've found the diamond plates are a bit "rough" on some of my knives and would like to get some benchstones that maybe do a better job just keeping them sharp, as opposed to having to remove metal (even the fine side seems a bit rough, maybe it's just me?).

As an example, I have a nice sporting knife with Bohler M390 and it takes a very keen edge, but I can't get it there w/o resorting to a fine ceramic rod. I'd prefer to use a benchstone though. Can you help? Would the Shaptons be a good fit? Would the 8" stones fit my DMT base?

I'm not opposed to starting from scratch...



Re: Switching from diamond plates to stones

Sun Dec 08, 2013 4:33 pm

The DMT plates are known for having random large diamonds mixed in with even the finer stones. Supposedly once they are "broken in" its less of an issue , but a water stone leaves a better scratch pattern. I would get this.

Nubatama 3 piece set.
And add some 2u or 1u CBN on Roo/Nanocloth to tackle the Vanadium Carbides.

You can just finish up with the CBN strop to clean things up , but you can also "dope" the stones with CBN to start tackling the carbides early on in the process... Slighty more advanced topic but worth mentioning.

Adding a 400 and 3k Nubatama to the set mentioned up top is a worthwhile upgrade IMO.
For handling steels like the M390 mentioned , Ken put it to me like this.

On a scale of 1 to 10
Waterstones are a 1
Shapton Pros are 1.5
Shapton Glass is a 2
CBN is a 9
Polycrystalline is a 10

This reflects my own experience / opinions on the matter :)

Re: Switching from diamond plates to stones

Sun Dec 08, 2013 8:50 pm

The fine diamond is perfect for your M390 blade and with proper use will yield extremely sharp edges. I would recommend a strop with 1 Micron diamond to finish after the diamond hone. Most waterstones won't hardly scratch the surface of most super steels. Coarse and medium stones to around 1k-2k will often work but after that its very hit or miss.

While the above recommendation for the Nubatama set is good for most knives it will not work to well with steels like M390. Again its not the coarse or medium stone but the fine (5k) stone where it would stop cutting. I've heard the shapton glass stones don't have too much of a problem with high end steels but I have never tried them.

I have however used DMT products for a long time and while the coarse/fine combo is great for most general use knives and folders it can at times be a bit coarse for some likings. The EF and EEF 8000 mesh DMT hone would be good to take things a bit further. The EEF produces a edge similar to a 3k-4k waterstone. If you have more simple steels like carbon or low alloy stainless then adding a set of waterstones wouldn't be a bad idea.

Re: Switching from diamond plates to stones

Sun Dec 08, 2013 9:21 pm

M390 and even moreso k390 have a good bit / lots of Vanadium carbides. Diamonds and CBN are going to be your friends here.

Depending on which Nubatama you are talking about I'd put them in the 1.5 to 2 range along with the Shaptons. All good stones but you are relying on removing the steel around the Vanadium carbides until the carbides fall out. Diamonds and CBN are a much better way to go here.

So you have several options. Diamond films work great here. Yea I know they aren't popular here :( Especially the heavy duty films are excellent for this task. So do CBN and diamonds on strops and belts if you are going with a powered approach. You can supplement your waterstones with CBN or diamonds in matching grits. This will make a far bigger difference than what stone you pick.

Diamond plates are essential for getting things started especially if you are reprofiling - changing bevel angles. I prefer the Atoma diamond plates as an excellent start. I don't care for the XXF DMT plates - I've had excessive diamond fallout and patina develop in excess on the nickel matrix supporting the diamonds. And the finish leaves a lot to be desired. I tried a couple of them before giving up on them. So this gets you to 1200 grit with either DMT (XF) or Atomas. From there (~ 16 microns) consider 8 micron CBN, then 4 then 2 microns. This will leave you with a very respectable edge, but of course you can go much further - 1, 0.5, 0.25 0.1 microns .... For the abrasion resistant steels, I prefer small jumps in grit sizes rather than big jumps.

I think jumping from ~ 16 microns (1200 is a bit coarser) to 1 micron (16,000) is way too big of a jump - especially on an abrasion resistant steel) and the XXF is again not something I've had much success with.

Given the right abrasives, sharpening M390 is no big deal. Given the wrong abrasives, it's a PITA as are most abrasion resistant steels. Personally I like abrasion resistant steels since steels that are abrasion resistant tend to hold the edge that you worked to achieve much longer.


Re: Switching from diamond plates to stones

Sun Dec 08, 2013 9:26 pm

The EF is 9 microns.


Re: Switching from diamond plates to stones

Sun Dec 08, 2013 9:37 pm

True (1200 mesh) and the EEF is 3 microns. Different grit rating systems drive me nuts. It's the EEF that I don't like if I was confusing. So still consider 8 micron CBN or if you want jump to 4.


Re: Switching from diamond plates to stones

Sun Dec 08, 2013 10:00 pm

Kens Diamond Films outperform the Shaptons , Pro or Glass by a wide margin when it comes to these steels (and even ceramics).

They leave an even scratch pattern , and cut FAST. They range from 165u all the way down to 0.1u. And they are cheap. You can add a pretty solid range of them to your collection for cheap , and just use em on ceramics and carbide rich steels. I love the ones I have , and have 4 more coming.

But for someone who just sharpens the odd knife that's carbide rich then the 3 piece Nubatama set is more than good enough when doped with CBN.
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