Hmmm... I would disagree. Having seen some file sharpened knives, they look just as ugly, or worse, than a pull-through carbide sharpener. A carbide bit is really the same thing as a file in this case.
If you are curious, you can find carbide sharpeners that are not simple preset angle pull-through types. These are freehand sharpeners, just like a file, but usually more compact. The ones I've seen seem marketed for in-the-field garden tool use. They do a great job with the right steel.
What you say isn't wrong. But having again seen knives used and sharpened for decades with pull-through sharpeners with lots of life left, the fact of shortening the life of a blade becomes more an academic point than a practical one. It's a nice reminder that my beloved knives are not quite as delicate as pressed flowers, even if I sometimes fall into the trap of treating them as though they were. And of course, using stones, or any other sharpening medium will do just as good a job of shortening the lifespan of a blade just as well as a carbide sharpener. The tool isn't at fault, so much as the user.
Not really, the similarities between the edge left by a file and that by a scraper begin with them being rough and end there. If you take a double-cut, 10" mill bastard to put an edge on a knife blade that's no more than .020" wide, then the teeth of the file themselves at that kind of coarseness will make induvidual contact with the edge instead of grinding it like an abrasive would. If you scale the file down to 6" single-cut, you will get a much finer edge. Still a lot rougher than you would get off of a benchstone though.
The difference between doing that with a single-cut file and getting a rough edge and a carbide scraper and getting a rough edge is that with a single-cut file you've actually removed metal, and grinded the edge away until the two sides met at the apex. What you've done is left a burr at that apex and tore it off, but in terms of the actual edge shape, it will still be there. Once all that burr and rough spot is gone, you're going to be left with a much better edge than that which has been sheared on through a carbide scraper.
So at the end of the day, a hand file may not produce an edge that is much sharper than a carbide scraper ( really depends on the files, I"ve got some #4 swiss needle files I'm sure would do a better job ), the hand file's edge is going to last a lot longer because it's an actual edge. The carbide scraper does nothing but rough up the apex of an edge until the metal goes from a worn, rounded form to sharp and jagged and will cut things. The difference is that once those sharp and jagged teeth where off, your knife is dull again, wear as the knife sharpened by the hand-file will just keep going and going. I would be surprised if it took the average carbide scraper user years to dull a knife sharpened by a hand-file to the point where they would think about pulling it through a carbide scraper, even though the finish result is just as good. The real difference is between cutting with a real edge and cutting with a burr left by shearing.
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. There are machines that cut metal by shearing it ( I operated one for a week or so ) and you have to be careful of how much engagement the piece has, the speed of the shearing motion, the pressure, angle of attack, etc. If just one of these things is off, the shear won't cut evenly, will leave bit striations, etc. Translate that kind of finicky operating on to the carbide V in a pull-through sharpener and it's no surprise to me that the edges would come out with ugly striations and big chunks ripped out, because that's what happens when shearing metal goes bad. I wouldn't be surprised if the guy who invented the carbide scraper was a machinist that had cut himself on a few too many sheared pieces.
I like the idea of a pull-through sharpener, I just don't agree with most of the way they're made. I've seen a lot of them with Arkansas stone wheels instead of carbide Vs that I liked; or even the ones with ceramic rods are okay. Carbide scrapers just shouldn't be part of the formula though. It's not "sharpening" anything, and really it's no different then running two knife edge's together until they're roughed up enough to cut something.
I think if these pull-through sharpeners would replace the carbide shears with diamond rod on one end, and ceramic on the other, it would do everyone a favor. I'm not saying that they would get edges as good as everyone else is since the technique is inherently substandard, but it will be a lot better than people tearing up their knives with carbide scrapers.
