Actually most kitchen knives are some variation of 420 steel, some 440. The Chinese and Europeans, etc have different nomenclature for it There are then some super duper hard specialty steels, most of which you wont run into on anything but very high dollar kitchen knives, more seen on fancy hunting knives, etc. Gross overkill for kitchen use unless you truly hate sharpening knives and want five year between sharpenings or something. And some junk mystery steels on the really low end knives. Those tend to be gummy and really hard to sharpen as the wire edge wont separate cleanly.
And of course quality/degree of the temper matters. Cheap knives can vary wildly. Just saying far as steel used, there isnt that much difference between your $10 Walmart special and your $100 German chef knife. Usually cheaper ones though similar steel, arent as well tempered. Cheap knives are fascinating though. When I was teaching myself how to sharpen, got quite the collection of thrift store and cheap knives. Maybe most frustrating were two knives I got for $1 each at Dollar Tree. You know only highest quality steel when you give whole $1 for a NEW retail chef knife.... Interestingly they werent the gummy mystery steel thats next to impossible to sharpen well. Not super hard temper either, kinda on soft side. I could sharpen them and they would stay sharp maybe a week at most. So kinda abandoned them but then ran across them again after lot more experience. Was looking and you know biggest problem, their geometry-profile. So as experiment, got out the angle grinder and gave one of them an approximation of a full flat grind. A large belt sander been better, my little sander fine for sharpening, not reprofiling. Then resharpened with belt sander. Interestingly the edge was still holding at a month. I didnt go beyond that. But proved a point that a sharp edge isnt everything. Geometry really matters.
Oh and far as seeing ragged edge, you really need a magnifying glass to compare edges. It will be obvious under magnification.
And no I havent known how to sharpen knife my whole life. Something like ten or fifteen years ago, got frustrated with almost sharp knives. And I tried several gadgets including one similar to what you gave link. Nope, still just almost sharp. Honestly thats about all gadgets can do is give you "almost sharp". I could do as well or better with angle grinder and very light touch. But edge has to be feathered out, not scraped, not almost sharp. Traditionally people sharpened knives with slow turning hand or pedal powered wheel with tin can water dripping on it, then lot stropping. Stropping can cure a multitude of sharpening mistakes or limitations. And this worked fairly well on plain carbon steel. But such manually powered grinders with large natural stone wheels not plentiful. Not as effective on stainless. Modern powered grinder is not a good thing for sharpening knives.
Oh another knife. My first wife brought it into marriage. It was an old no name carbon steel knife, the kind that turn black and rust easily if not oiled after use. She got it at local grocery store when she got her first apartment long before we were married. That was our only sharp knife for lot years. And I could get it almost sharp, well sharp enough to use but didnt feel really sharp. Butcher knife, but we used it for everything. Oh that thing was frustrating. It was still here when we parted, but then disappeared. Well when my old refrigerator finally quit, and I was dragging it out the door, that knife fell out of the evaporation pan under the refrigerator. No idea how it got there.. and it was pretty rusty. But said ok, lets have go at the old FRUSTRATION. Oh it wasnt even much of a challenge. Cleaned up and razor sharp lickety split with the belt sander. Plain carbon steel knives tend to be really easy to sharpen and it was. Sure that was first time in its history that it was truly sharp. This was the knife that resisted all gadgets and grinders and such.
Oh mentioned it in another thread sometime back, was just looking at cheap knives at Walmart for entertainment. And saw one of those commercial NSF rated white plastic handle knives like they use for production work at restaurants. A Tramontina Pro (made in Brazil), probably only non Chinese knife they had. But it had full flat grind and distal taper, something not seen often in the cheapies. Not fond of plastic handles but got it, like $8. A truly impressive knife for the money. Similar Victorinox has nothing on it. It was actually very sharp new out of the package. I used it for while like that, pretty sure it was a six month to year type knife far as retaining an edge. Then was sharpening another knife and sharpened it too. Even better.
Oh my favorite knifes are the German or Spanish Henckels chef knives or the Wusthof. They have some heft. The Spanish Henckels are really the bargain, can find them used under $15. New they are around $60. I cant see the German ones are that much better, though German ones have better fit and finish. Full flat grind and distal taper. Can be taken from blunt to very sharp fairly fast. Whats truly a shame are some of thin bladed Japanese knives when clueless people try to sharpen them. they dont withstand sharpening abuse nearly as well as the heavy knives and definitely suffer with gadget sharpening.. So usually see used ones with really wonky wavy edge. Or at least a very worn down edge. I have a MAC original that is quite nice. Not as fond of flat bottom "slider" knives but its ok. That thin flat grind blade when sharp is quite amazing. I swear it will handle hard shell squash as well if not better than the Wusthof or Henckels. Thats why the MAC originals got reputation for staying sharp long time. They didnt really, not super special steel, but good steel combined with excellent thin blade geometry, made them feel sharp long time.
). But with multi toothed tooling the controlled setups were not optional and the cutting angle critical for longevity, strength and finish. For wood or steel. But I freehand when sharpening knife blades. I have tried one of those kits that you clamp a knife blade into and there is a rod that screws into the various stones and through a guide to control the angle. What a PITB to use but it does what it is purposed to do. That's why I really liked the video you posted of this product.
