Can't make ceramic knife shave!

fulloflead

fulloflead

Joined
May 3, 2002
Messages
6,192
I recently received a Boker Infinity ceramic-blade knife in a trade from a fellow BF member LNIB. It's dull as hell!
I have no doubt that it is indeed LNIB and has never been used. It's just that the factory edge really sucks! It won't even cut paper!

Not to toot my own horn but...;)
I'm a REALLY good knife sharpener and have great stropping skills. I can make a steel blade sharp enough to sever a suspended hair fairly easily within about 45 minutes from being fairly dull. I just LOVE to sharpen good steels, especially D2 which I've had exceptional luck with. I've spent the last couple years perfecting my sharpening skills and I'm REALLY anal about my edges and I own no knife that won't at least shave hair at any given time.

With that said...
I can't sharpen this ceramic blade worth a crap! I've been working on it for almost 2 hours with a Gatco/Lansky combo diamond system and I'm NOT happy!:(

I've still got it locked up in the set but I think I could MAYBE get it to cut paper if I'm lucky if I took it out.

Normally, I'd work the edge over to a burr on each side and then lower the grit and continue until I got to a ceramic grit and then strop it until I could take one of my girlfriends hairs out of her hairbrush and practically fillet it.

Obviously, the burr doesn't come into play in this case so it's harder. Much harder. Also, obviously, stropping would have no effect even if I tried.

Really, I'm beside myself and I'm going crazy over it.:eek:
 
I've only heard problems with sharpening ceramic knives...the only thing I could offer would be a search for ceramic sharpening.

Wish I could help but I have stayed away from ceramics for the this reason alone...and that I drop knives lol.
 
fulloflead, as I understand the problem, the only eventual effect you will have on that knife is to get the edge to begin spontaneously chipping :( I have a nice Boker ceramic folder, also. The factory edge is OK on vegetables, nice on fruit, cleans up well ... a razor it is not, and will never be. Ceramic won't hold a razor edge. Pieces will flake off a ceramic edge if it's too thin.

So ceramic knives are made fairly sharp, but not very. Their advantage is, they're sharp enough for most food prep, without being a hazard to clumsy cooks. The edge they do have will last a long time. They clean up easily, and don't impart a metallic taste to foods.
 
Originally posted by Esav Benyamin
fulloflead, as I understand the problem, the only eventual effect you will have on that knife is to get the edge to begin spontaneously chipping :( I have a nice Boker ceramic folder, also. The factory edge is OK on vegetables, nice on fruit, cleans up well ... a razor it is not, and will never be. Ceramic won't hold a razor edge. Pieces will flake off a ceramic edge if it's too thin.

So ceramic knives are made fairly sharp, but not very. Their advantage is, they're sharp enough for most food prep, without being a hazard to clumsy cooks. The edge they do have will last a long time. They clean up easily, and don't impart a metallic taste to foods.
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I was hoping you wouldn't say that.

It was a very good answer so I'll take it point by point:

I've noticed that my sharpening has made the edge slightly more toothy. (Chipping.) Slightly.

I'm sure it would be good for kitchen use, but it's a pocket knife; supposedly designed as an EDC knife.

"a razor it is not, and will never be". OK, but I've read reviews that said it was shaving-sharp out of the box. I guess I shouldn't have believed it.

I'm sure the edge does last a long time, but it's not worth it to me if it's not sharp to begin with. I can neglect my steel knives and sharpen them after they get DULL and still be better off.

It seems, from your post, that I'm expecting too much. If that's true than I'll have to accept that, but I was hoping for at LEAST a shaving edge.

I suppose that, since I have such high sharpness standards, that this knife is not for me.

I regret trying to sharpen it now because I can no longer sell it or trade it as LNIB. I'll have to explain what I did since I'll probably now sell or trade it.

(Any takers?)

Thanks, by the way.
 
Despite the folder configuration, ceramic blades are not real good EDC. A very short blade might be ok for minor office EDC, like string, tape, boxes. Don't think of prying or chopping, even lightly. Mine is the Boker Delta, which is a slightly longer blade than most -- just over 3".
 
Originally posted by Esav Benyamin
Despite the folder configuration, ceramic blades are not real good EDC. A very short blade might be ok for minor office EDC, like string, tape, boxes. Don't think of prying or chopping, even lightly. Mine is the Boker Delta, which is a slightly longer blade than most -- just over 3".
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Yeah. If I can't sell or trade mine I'll probably just keep it on my desk for opening packages and such.

If the knife was TOTALLY non-magnetic it would probably have a claim to fame, but it does have a HUGE pivot screw and steel liner and pocket clip.

Novelty item I guess.
 
From what I understand from my research on ceramic blades - you can't get a very fine angle on the blade, it's too brittle for that. And when sharpening the blade must be polished , any scratches on the edge may act as stress concentrations and cause cracking. I'll stick to steel.
 
Ceramic knives can be made shaving sharp, as I have used such blades, and sharpen them after blunting to such an edge. Ceramics can be ground with any abrasive, I have reworked tips and removed large chunks out of the blade with cheap AO belts (slower than steel, but still possible).

However they do not respond well to a coarse edge, not that they get tremendously brittle, they simply are not aggressive. You need to really refine the finish, so you will want fine abrasives, DMT diamond paste, micron sandpaper, CrO or a combination of all three.

Do not make large skips when sharpening in grit (jump from 1000 to 8000) as it takes a long time to remove the scratch pattern as ceramic machines very slowly. This is also true for steels, but more of a problem with ceramics as they just work slower.

Similar with steels, also make sure you are honing at the right edge angle, check with a marker and look at the edge under magnification if possible (even 10-20x is fine). You should see a gradual refinement of the scratch pattern. You also have no burr problem to deal with unlike in steels.

The upside of course is that once you get it sharpened you won't have to sharpen it again until you damage the edge. Unless you are cutting very abrasive material (like sandpaper), the edge will last until you chip it.

There are also some specific comments in the OK-45 review :

http://www.physics.mun.ca/~sstamp/knives/ok_45.html


-Cliff
 
Originally posted by Cliff Stamp
Ceramic knives can be made shaving sharp, as I have used such blades, and sharpen them after blunting to such an edge. Ceramics can be ground with any abrasive, I have reworked tips and removed large chunks out of the blade with cheap AO belts (slower than steel, but still possible).

However they do not respond well to a coarse edge, not that they get tremendously brittle, they simply are not aggressive. You need to really refine the finish, so you will want fine abrasives, DMT diamond paste, micron sandpaper, CrO or a combination of all three.

Do not make large skips when sharpening in grit (jump from 1000 to 8000) as it takes a long time to remove the scratch pattern as ceramic machines very slowly. This is also true for steels, but more of a problem with ceramics as they just work slower.
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Ouch! Sounds like a lot of work. I may give it another whirl though.

Similar with steels, also make sure you are honing at the right edge angle, check with a marker and look at the edge under magnification if possible (even 10-20x is fine). You should see a gradual refinement of the scratch pattern. You also have no burr problem to deal with unlike in steels.[/B]
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I did exactly that very thing, but I'm guessing that the fine diamond stone I finished with still was way too coarse. I may have to wrap my ceramic stone with some CrO really fine sandpaper and go at it that way.
 
Yes, fine diamond, specifically 1200 DMT is still far too coarse, that should be able to slice paper, but that is still a far ways from optimal (50% or less). Moving from that diamond to CrO is too much of a jump, that is a factor of ten in abrasive size, you want to optimally keep it to two or so.

-Cliff
 
Originally posted by Cliff Stamp
Yes, fine diamond, specifically 1200 DMT is still far too coarse, that should be able to slice paper, but that is still a far ways from optimal (50% or less). Moving from that diamond to CrO is too much of a jump, that is a factor of ten in abrasive size, you want to optimally keep it to two or so.

-Cliff
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You're making me tired just reading it.;) Now, not only is it going to take me another several hours; I have to go out and buy stuff. I might do it just to have the experience - I like to agonize over little things like this sometimes - but it's going on the sell/trade block and if it's gone before I finish, so be it.

Where do you suggest I get the grits? Various CrO sandpapers? I don't have a belt sander and I prefer my clamp systems Lansky/Gatco.
 
It actually doesn't take very long with the right abrasives, a few minutes depending on skill, how consistent you are and so on. I blunted the OK-45 horribly fooling with it cutting ceramic and had it restored to cutting paper well in under five mintutes, which included the set up time of cutting sandpaper into strips (which I did with the knife).

Now if you have chips in the edge it will take some time to remove them, you would want a belt sander to do that well, or a really coarse abrasive (I just use sanding belts manually sometimes, you can get them really coarse like 80 grit and make files out of them). But otherwise sharpening should only be a matter of minutes, unless you are shaping an edge sharpening requires a minimal of material removal.

You can buy DMT pastes in various grits 9,6,1, or use very fine waterstones, 4000,6000,8000 then finish on CrO, or use various Micron SIC or diamond sandpaper, 15, 5, 0.5, 0.3 micron are available. The sandpaper is by far cheaper in the short term, the waterstones are cheaper in the long run.

-Cliff
 
I have a Boker 2031
2031.gif
had it since they first came out 10 12 years ago, It's not shaving sharp but it will slice paper clean all day long, flesh:eek: , fruit, cardboard, and meat.

I don't know if it's because it's thinner but it does cut like crazy.

As far as sharpening it, what cliff and every one else says is true, it has to be smooth and polished, I've had a lot luck with my EdgePro, but I attribute a lot of that to the fact that I'm using water stones, don't give up.
 
Sorry to convey bad news but you probably won't be able to get an edge on the ceramic. All diamond sharpeners use PLATED diamonds, that is, they are bonded to the substrate (steel) in a Nickel/ Chrome plating.
No matter how fine the diamond, the bond type will chip the ceramic, even at a micro level. Factories use a RESIN bonded diamond wheel, which holds the diamonds (or Borazon) in a hard but flexible epoxy-like matrix. This cushions the particles and provides a shiny surface and a true, unchipped cutting edge, far smoother than even a polished steel edge.
There are knife shops that re-edge ceramic, but I'll be damned if I know of one. Perhaps Boker can help. Good Luck, BOB
 
T. Erdelyi, most ceramic blades don't come very sharp, compared to steel anyway, even the high end ones. I had a custom from McClung and it was not as sharp as the low end production blades. However Kyocera is an exception, their ceramics (from what I have seen) come as sharp as the better production steel knives, and the edge geometries are better than most in regards to cutting efficiency. Just like steel, you can get ceramic blades of various qualities.


-Cliff
 
Maybe it's the makers of ceramic-ware for not informing the public what the knives are useful for. A good ceraminc knife, cutting materials it was meant for, can cut and cut for an exceptionally long time and become a very useful tool in that regard. When folks think it's used for other materials and attempt to change the blade edge accordingly, they experience problems like the thread-starter, who unfortunatly might have messed the knife up for resale.

I would say to get the knife into it's optimum condition and just have it available for those cutting jobs that it can excel at, and then simply enjoy it's abilities to continue cutting a long time between sharpenings.


Edited to add: As Bob T says, perhaps special sharpening materials are needed. Shannon at MD Tactical sells a diamond benchstone recommended for the ceramics that Mad Dog uses; alternatively, I sent a "very used" (beat up) MD ceramic to Mad Dog for resharpening and it came back like a brand new knife. I mean, real brand new edge - all perfect and polished up, ready for another lifetime of cutting.
 
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