Does this kind of sharpener even WORK?!

cziv said:
I've seen several ceramic pull throughs. Haven't tested any of them yet. :confused:
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While I would not recommend anyone here buy one, I have used one in a previous life...and they are not that bad. The key is to use the weight of the knife and nothing more.

Make no mistake, they are NOTHING compared to a proper sharpening job, but on a cheap fillet knife, it can make the difference between clean(ish) fillets and jagged shards of bass that look like they were carved with a claw hammer.
 
unit said:
While I would not recommend anyone here buy one, I have used one in a previous life...and they are not that bad. The key is to use the weight of the knife and nothing more.
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I had excellent results on my SAK & LM Wave with my DMT pocket sharpener (crossed ceramic sticks) but I also would not recommend it to anyone here. I got sick of cleaning the ceramic sticks (they blackened on every stroke) and the angle which worked well on my SAK & LM didn't work on almost every other knife I had. My home-made paddle strop works well on EVERY knife I own and is quicker & easier than the crossed crock sticks, it is also cheaper.
 
KennyB said:
Shearing metal off is not the same as abrading it. The main difference with it is that you have one active metal cutting surface that is supposed to accurately and finely shape another, and that kind of operation just doesn't work out too well without a lot of extra control.
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I think you're getting twisted up in definitions. A carbide scraper works exactly the same way a file works. It scrapes away metal. It even works the same way a microscopic grit of diamond works. There are differences in scale. And that difference is important. But that is all. The scraper takes off large shavings in one pass. The files, provided it's hard enough, takes off multiple smaller shavings in one pass. A single microscopic diamond scrapes off a microscopic amount of steel in one pass. The difference is that nobody is likely to use a single microscopic shard of diamond, but rather thousands at a time, bonded to a substrate, to scrape away thousands of tiny bits of steel at a time.

In usage, the difference between a file and a carbide scraper and just about any other medium is a matter of coarseness. If you could concoct a tungsten carbide mill bastard file, it would function the same as a regular carbide sharpener, just much faster. And if you could bond millions of microscopic shards of carbide into a block, you'd have a sharpening stone. What they all would do to a steel blade is the same. The difference is the amount of refinement in the result.
 
shecky said:
I think you're getting twisted up in definitions. A carbide scraper works exactly the same way a file works. It scrapes away metal. It even works the same way a microscopic grit of diamond works. There are differences in scale. And that difference is important. But that is all. The scraper takes off large shavings in one pass. The files, provided it's hard enough, takes off multiple smaller shavings in one pass. A single microscopic diamond scrapes off a microscopic amount of steel in one pass. The difference is that nobody is likely to use a single microscopic shard of diamond, but rather thousands at a time, bonded to a substrate, to scrape away thousands of tiny bits of steel at a time.

In usage, the difference between a file and a carbide scraper and just about any other medium is a matter of coarseness. If you could concoct a tungsten carbide mill bastard file, it would function the same as a regular carbide sharpener, just much faster. And if you could bond millions of microscopic shards of carbide into a block, you'd have a sharpening stone. What they all would do to a steel blade is the same. The difference is the amount of refinement in the result.
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Well, not to get caught up semantics, but when you're working with metal and you use a single, hard metal surface to cut another piece of metal in the fashion a carbide insert removes the metal off steel, it's often called "shearing" because the hard 90 degree corner of the carbide is pushing metal off through pressure and movement. It does very little cutting, as it actually just pushes material out of the way. The problem is that some material doesn't want to be pushed out of the way, so you wind up with rough spots ( striations ), binding, etc.

Something like the teeth on the file actually cut into metal and penetrate it. The actual difference between shearing and cutting is minimal, but with the teeth on the files the real difference is that they don't try to push material straight off of a surface; the teeth cut into the surface in a triangular fashion, and then more teeth come in behind to cut the peeks and valleys that the other tooth pushed up while cutting. If you wanted to compare a file to shearing, a file would basically be thousands of tiny shears all with their own clean-up right behind them. Files are cut in such patterns that the teeth do the rest of the work that the one in front started. If you think of a single-cut file, those teeth are very much like shears, but the fact still remains that there are hundreds of shears there and they all have to clean up after each other for a file to make a finely cut surface. If you had a file with just one really hard tooth, it would shear metal very well at all; it wouldn't make good contact at some points, it would just raise and displace metal at other spots, etc.

So yes, shearing and abrading are very different, yet not really all that different. Yet we still call them "shearing" and "abrading" because they are two distinct operations; one might say that shearing is part of abrasion. When you look at abrasives instead of files, you wind up with a much more random pattern of "teeth" that are doing the cutting, but it's still distributed in such a way that while some abrasive is cutting and shearing metal off, there's more abrasive behind it cutting off the high spots and displacement that the shearing is causing by doing its own shearing. Abrading is more like double-shearing.

The problem is that you're just not going to get the edge refined with a carbide scraper unless you're extremely careful. One little change in the angle the edge is passing through the V at will bind and twist the edge in the inserts, and then the shearing action itself will tend to leave pieces behind. At this kind of scale I think carbide would stay uniformly hard enough to avoid raising high spots, but if you ever watch a large-scale shearing operating you could see how just the most minute change in angle of attack, cutting depth, etc can lead to a part being sheared cleanly, and then other times the shear will basically bounce down the metal surface as it shears some, the metal resists and binds, and the shear jumps over that little bit of metal and does it again. If you look at the edge of some knives done by a carbide scraper, you can see the same kind of alternating pattern where the metal binds, the scraper "jumps" over the material and it just does it the whole way down the edge, and because of this binding and jumping it's near impossible to hold equal pressure and you'll see little dents, scraps of metal hanging off or at the very best case scenario a change in the finish or straightness of the edge that goes in a distinct alternating pattern down the edge.

At the end of the day, supposing that you were really careful with the scrapers, made sure to run the knife through in a perfectly straight line, used just the right amount of pressure, used just the right amount of consistency, etc. You will still be left with a burr on one side, and how are you going to take care of that?

If they work for people then all that really means is that some people can use an edge that is the antithesis of "refined", and that really wouldn't be very surprising given the way people take to very coarse edges and serrated knives. A rough, saw like edge isn't exactly undesirable, but what you can't really avoid is that the carbide scrapers are imprecise and tear up the edge, leaving it to basically be a scrap-metal saw. Yes that will cut things, and yes that's what most people need their knife to do, but I don't think that people should settle for that.

I mean, as far as people that use them to get a servicable edge really quick and that are satisfied with them, that's all fine and dandy. However, what about the guy that doesn't realize that they're going to tear his edge up more than sharpen it? He's going to go to the store looking for a stone to hone his already pretty sharp edge up on, buy one of these pull-through things, read the instructions, and then just completely destroy his edge "sharpening" it. Then once the results he gets are sub-par, he'll think, "Well, this thing didn't work at all, I think it made it worse," and will have to go back to the store, return it, buy a stone, and then what? Discover the carbide did too much damage to fix with the little Arkansas stone he bought?

Personally, I'd rather let people know that these sharpeners are crap then have someone go through that.

Besides, these types of sharpeners will always have diminishing returns. The first time you use it, it's going to be on a decent edge. The more you use it, the more you degrade that decent edge down and down until one of these carbide scrapers won't do squat. Then what? Throw the knife away and get a new one? That's why they shorten the life of a knife, because most people don't realize they have diminishing returns, and that once the knife won't get sharp that it's not a problem with the knife being "worn out" or the sharpener being "worn out" but with the sharpener itself.

I mean, I suppose they can be time savers, but they're just overpriced time savers. If I'm out in the field and think, "I need an edge now, and I don't care if I screw my blade up," I'm going to grab a piece of glass, the bottom of a coffee mug, hell I've scraped on the hard corner of one of my other knives. The difference is that I didn't spend extra on a gadget to ruin the edge, and I don't think anyone else should either. If people want to touch their knives up quickly in the kitchen with no regard to what damage they're doing to the edge, then buy a $5 grooved steel. The only real difference between that and the pull-through sharpener is the illusion that the pull-through sharpener is easier to use. In all honesty, using a kitchen steel in a proper way is a bit complicated; using it in a way that will get you an edge that a carbide scraper will get you is as simple as mimicking what you've seen in the movies.

I guess in the end it's all up to what the user wants to do, but I just don't think saying, "Well, it's good enough for you want," is a service. It doesn't clue them in on the fact that they're damaging the blade ( even if it is by a small and trivial amount ), and that eventually it's not going to work. What about when they can't get a knife sharp with them anymore? Do we ever say, "Well, they will thicken the edge out over time and will eventually stop sharpening the knives well," or just leave them to assume that either the knife or the sharpener has reached the end of its life?

To me they're just over-priced gimmicks and there's better, cheaper ways to get a working edge despite doing damage to the edge in the meantime.
 
thats what i was trying to say but in a shorter post. as a last ditch effort,yes use them. but as a "be all and end all" dont.
 
and btw, have you guys noticed that the op is long gone? if youre still here bud ,we are here to try to help. just asking.
 
I checked his profile just for sh_ts and giggles. Since this thread was started in 2007...

He hasn't posted on BF since March of 2009.
 
On a side note, the kind of sharpeners that are large (Tall) enough to be used as mini crock sticks are pretty good. Lansky makes one IIRC-it's ceramic. Looks a lot like a pull through but isn't.
 
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