carbide tear out and ceramic

D

davek14

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May 30, 2009
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People have spoken of the harder steels being sharpened better with a harder medium. The idea being that the carbides in the steel are actually cut whereas with a softer medium the matrix is eroded and you get carbide tear out.

Whether you believe in carbide tear out or not is not the discussion I intend to start.

I'm far from a great sharpener. I use a lot of carbon steel and other simpler alloys.

I recently purchased a diamond rod to work with my D2 blades and it's great. It seems to be sharpening some problematic 440A better as well.

My question is this. The diamond rod works quite well but it leaves a rough, toothy edge. I know D2 does best with a toothy edge but it could be refined at least a little, plus I have other knives.

I'm not going to purchase anything else at this time. When I do, do you think some diamond compound for a strop would be enough?

For now, I want to refine the edge with what I have. I have some fine stones and I use ceramic rods a lot. The edges seem to get duller when I try to refine them. Is ceramic hard enough to refine an edge with large carbides?
 
davek14 said:
People have spoken of the harder steels being sharpened better with a harder medium. The idea being that the carbides in the steel are actually cut whereas with a softer medium the matrix is eroded and you get carbide tear out.

Whether you believe in carbide tear out or not is not the discussion I intend to start.

I'm far from a great sharpener. I use a lot of carbon steel and other simpler alloys.

I recently purchased a diamond rod to work with my D2 blades and it's great. It seems to be sharpening some problematic 440A better as well.

My question is this. The diamond rod works quite well but it leaves a rough, toothy edge. I know D2 does best with a toothy edge but it could be refined at least a little, plus I have other knives.

I'm not going to purchase anything else at this time. When I do, do you think some diamond compound for a strop would be enough?

For now, I want to refine the edge with what I have. I have some fine stones and I use ceramic rods a lot. The edges seem to get duller when I try to refine them. Is ceramic hard enough to refine an edge with large carbides?
Click to expand...

I would say 'sort of', or 'up to a point', to that question. Technically, the alumina in ceramics is hard enough to abrade the large chromium carbides in D2. But it'll do it slower, and won't have the same efficient ability to cleanly cut and crisply shape large carbides at the edge, like diamond (or CBN) can do. If technique isn't perfectly steady from one stroke to the next, it's very easy to round off a crisp apex on ceramics, as you've apparently noticed ("edges seem to get duller when I try to refine them"). The large and very hard chromium carbides act sort of like 'cobbles' (stones) in concrete aggregate, and they'll resist abrasion much more than the finer & softer cement (as the matrix steel in a blade) which binds the 'cobbles' in place. The cobbles will tend to be burnished, polished and rounded as a result of abrasion with inadequately hard grit.

If you're not liking the toothiness of the edge coming off the diamond rod, you might consider refining with finer-grit diamond hones (EF, EEF) and hard strops using diamond compound on wood, like balsa, basswood, etc. Most diamond rods are around 600-grit (usually called 'Fine'), which is pretty toothy; even more so with polycrystalline 600-grit diamond, as used on some brands like EZE-Lap. Finishing with DMT'S EF (1200) diamond will begin to approximate the finish left by a medium ceramic like Spyderco's brown/grey hones, and an EEF (8000 mesh in DMT's version) will bring the finish very close to mirror (hazy) on most steels. At the same time, they'll also leave the edge much crisper, because they cut and shape the carbides with ease, without ripping them out of the edge.

D2 DOES do just as well with a polished edge, BTW: almost all of my D2 blades have eventually ended up as such, as I've found it just keeps getting sharper with careful refinement to a polished finish. Many will say it doesn't, but I think the true obstacle is just the time & patience needed to get it there (many aren't willing), and it'll be frustrating if done with inadequate tools. It's a great steel that responds well to most any finish, so long as it's refined with the right tools (abrasives) and with patience.


David
 
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I experience the same 'rounding' using ceramic (Spyderco UF) on my D2. With good advices from David, Martin & Luong, I settled happily with DMT EF & a bit of micro using EEF. My technique certainly needs improvement.
 
I'd say the largest impediment would be on the larger carbides ceramic begins to drop off when it comes to abrasive potential and you end up with increasing amounts of burnishing. It will work fine as long as you stay very close to the target angle but if it turns into a microbevel or if your applied pressure is too high, the odds of carbide blow out increase.
 
Thanks very much (especially to Dave) for the answers.

So my best bet is to get a 1200 grit diamond plate. Anything I can do right now? What about fine grit emery? Same problems as ceramic?
 
I've been sharpening on F and EF Diamond plates and then finishing on a strop with 1 micron diamond paste. For a while I was also using an EEF Diamond plate before stropping, but I'm not sure I saw the benefit. I've had results that are satisfying to me on every steel I've used this on which includes VG10, S30V, D2, and S90V. The VG10 knives are Japanese kitchen knives, and the other steels are all on Benchmade folders.
 
davek14 said:
Thanks very much (especially to Dave) for the answers.

So my best bet is to get a 1200 grit diamond plate. Anything I can do right now? What about fine grit emery? Same problems as ceramic?
Click to expand...

If looking for some more polish after your diamond rod, and in the absence of the 1200 diamond, you might try a hard strop of balsa or basswood, or similar smooth & tight-grained wood. Use a metal polish like Flitz, Simichrome or Mother's Mag Polishing Paste on the wood strop. The combination of one of those compounds on wood works very well (& fast) on D2 and other steels, and can leave edges very, very crisp & sharp. the hard backing for the compound is more critical for D2, so the compound works aggressively enough to avoid rounding off the apex. Could also try the same compounds on a hard (wood-backed) strop of denim or linen glued to the wood (contact cement is good for this). Keep the angle controlled, and don't exert too much pressure on the strop (again, to avoid rounding the apex).


David
 
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