So I picked up a
CATRA Catrahone after seeing it mentioned in this thread.
CATRA is an old style trade association that's now branched into industrial knife sharpeners, materials analysis, consultancy, and a lot more. The Catrahone is their domestic powered knife sharpener that claims to make a knife up to nearly 90 percent as sharp as new, and keeps that edge for 200 percent longer that other sharpeners. It's currently selling directly from CATRA for £75 including postage, which is about half the price of other brand name powered knife sharpeners.
It's basically a small 24 volt motor with a shaft containing three sets of offset diamond grinding wheels, all encased in a black plastic housing with a base and a removable magnet to catch any filings. It's right handed, but you can specify a left-handed version if you need it. There's a universal plug that you just clip the correct prongs to, and no power switch. You plug it in, turn it on, and it runs. It's actually very quiet in operation (just makes a humming noise), but gets noisy when you put a knife into it. The bigger the knife, and the coarser the grinding wheel, the noisier it gets. It's set to a permanent 34/17 degree grind, and isn't adjustable. It looks and feels like something from a company that is all about the function, and little about the form. It's not going to be advertised as a pretty kitchen lifestyle product.
Usage is pretty simple, you just slide the blade of the knife back and forth in the grinding slots. The coarse slot will reprofile an edge and grind out any chips or dinks, and is really only needed for a very blunt or damaged knife. The second set of wheels are for sharpening to a cutting edge, and the third to polish and hone the final edge. After an initial grinding on the roughest wheel and then the sharpening/honing wheels, a few strokes on the sharpening/honing wheels once or twice a month is all that's needed for normal usage.
I found that it worked really well without scuffing the sides of even coated (coloured) blades. Even some really heavy knives that the wife bought and never really liked could be reprofiled and given much better edges. Knives that I previously couldn't get good edges near the curved points were easily sharpened. The offset sharpening wheels means that you miss the points and backs of the knife where the wheels on one side don't reach all the way down the blade. This isn't a problem with the points, as you can just draw the knife all the way through the slot. On the bottom (nearest the handle) of the blade, you could do the same, but on some knives the bloster or shape of the blade/handle meant it lifted out of the slot and you'd get 5 mm (10 mm on my huge knives) where the left side of the sharpening wheel can't reach all the way down the blade. The bolster either stopped it going far enough into the slot, or made it ride up over the slot. On most of my knives, there's enough clearance to go all the way through. I found it difficult to round any points, as the sharpener actually can sharpen the end of the point too. I found the thinner knives sharpened better, but that just may have been my impatience, as our very heavy knives probably just needed more effort as there is just more metal to grind than on our normal knives.
You can pretty much sharpen any blade (not ceramics), but the likes of scissors won't fit unless you can take them apart, and serrated blades will pretty much only get the points of the teeth sharpened. As those tend to actually do most of the cutting, that may be enough for you. Being able to sharpen your other knives so well means you're more likely to start cutting soft things with straight edges. You don't need a bread knife to get a nice slice, if your normal knives are so sharp. I didn't manage to heat any of the blade edges up during sharpening, except near the point of one long knife that I worked on quite a lot, and that got slightly warm to touch, but nowhere near the heat of hot food. Sharpening with the likes of bench grinders can supposedly damage the tempering of the blade edge by overheating them, thus meaning they wear more quickly, and the Catrahone is specifically stated to avoid that, presumably by running at low speed and only working on a very small part of the blade edge at any moment.
So will you end up with a blade that can cut paper in mid-air and shave your arm with? No, but you will get nearly all the way there. A few more minutes with a fine stone or a strop will probably give you that last bit of razor's edge. For most people, that's probably not necessary, and a fine edge like that will likely be damaged as soon as you cut into a chopping board. What you will get is a good, sharp working edge that lasts a long time, that's very practical for kitchen use.
So if (like me) you're rubbish at sharpening with a stone, don't want to spend the time to learn the skills, and just want a sharp knife with minimal effort, this is a great product at a sensible price. If you're a real perfectionist but don't want to spend an hour sharpening a knife, a Catrahone will do all the heavy lifting and leave you with the last bit of stropping/polishing. If you're into the whole zen thing of hand sharpening, learning the skill of sharpening, and getting a scalpel edge, then this probably isn't for you.
To be honest, it does feel like a bench grinder that's been redesigned specifically for use with knives, and then shrunk for use in a domestic kitchen. It's got a satisfying heft to it, and feels like it's really working. The set grinding angle may be a limitation for purists, but it means you don't have to worry about getting angles or sharpening strokes perfect, or scuffing up the sides of your knife. I've had a go at it with cheap kitchen knives of every shape, heavy thick quality knives (including a cleaver), a tactical knife with half serrations, serrated bread knives, scissors (took them apart), micro serrated knives, coated knives, etc and I've been pretty happy with the results. Some knives that I don't have to test might not work because they have weirdly curved blades that I can't see how you can fit into and around the sharpener (such as kerambits or gutting knives), but that sort of exotica isn't really used in the kitchen.
So if you're looking for a powered knife sharpener for your kitchen, the Catrahone should be at the top of your list, especially for it's current price not being much more than a lot of cheap and not-very-good hand sharpeners (or less than things like the the Spyderco or Lansky hand sharpening systems), and there is a money back guarantee if you don't like it. It's a sharpener for people who like to have sharp knives, rather than for people who like to sharpen knives.