Sharpening without scratching
January 7, 2010 2:49 AM   Subscribe

How to keep an electric knife sharpener from scratching the blade?

I'm thinking of getting a knife sharpener. As a test, I ran a couple dulled "sacrificial" knives through a friend's (practically new) sharpener (model).

The edge is definitely sharp, no worries there, but the sides of the blade have several scratches in them, which I'm really concerned about. I like sharp knives, but for sentimental and aesthetic reasons, I also don't want my good ones getting beat up.

Other than, of course, just taking them to a knife shop, which I have done before now, are at-home electric sharpeners doomed to damage blades? Is there something I could do about the technique for pulling the blade through, or some modification to the sharpener itself, that would prevent the blade from getting damaged?
posted by Blazecock Pileon to Home & Garden (24 answers total) 1 user marked this as a favorite
Response by poster: I have also tried a sharpening stone, but because of poor technique I just can't get a good edge. I cut out a little cardboard "triangle" to remind my hand to run the blade over the stone at the correct angle, but for whatever reason, the edge doesn't get as sharp as I'd like. The electric sharpeners seem attractive because of their pre-angled guides.
posted by Blazecock Pileon at 2:58 AM on January 7, 2010

Think about it like this:
Do you try to sharpen your used razors at home? Why or why not?

Someone explained it top me one time like this:

Metal will eventually lose its edge. After so many choppings and hackings and slicings, the edge of the metal rounds off. It just does. It rounds off so much that now you are trying to cut things with a stick made of metal. You'd be better off trying it with a bread knife.

What you are doing with the sharpener and with the stone is trying to put more teeth on a saw blade, giving it tiny serrations. That's the scratches that you see on the sides of the blade.

At some point, you have to grind that ax. I mean you must take it to a professional blade sharpener in your town. The pros will put it to a bench grinder and restore the edge.
Retail sharpeners and wands and whatever are only meant to give your blade new microscopic teeth, not to return it to its full glory.
posted by at the crossroads at 3:24 AM on January 7, 2010

What you are doing with these sharpeners and stones is called "honing."
At some point all the honing in the world won't save a blade that needs re-sharpening.
To resharpen a blade, take it to a specialty kitchen shop. (Someone earlier in AskMe said Sur la Table does it.) The local shop here in my town does it for $2 a blade.
posted by at the crossroads at 3:35 AM on January 7, 2010

Response by poster: What you are doing with these sharpeners and stones is called "honing."

No, honing is straightening an edge. Electric or manual sharpeners or whetstones grind away metal.

I'm not asking about honing or about taking the blade to a "pro".
posted by Blazecock Pileon at 4:27 AM on January 7, 2010

Best answer: I'm not sure I understand what at the crossroads means - I don't see how grinding with a whetstone is different from grinding with a bench grinder, except for the bench grinder being faster. I'll admit, though, that you could buy a lot of $2 knife-sharpenings for the cost of a $170 knife sharpening machine.

I've never used a knife sharpening machine like the one pictured, but the usual thing to do when you're working on something you don't want scratched is to cover it with a protective mask - such as electrical tape. Would masking the knife's non-blade areas work on your friend's sharpener?
posted by Mike1024 at 4:32 AM on January 7, 2010

Response by poster: the usual thing to do when you're working on something you don't want scratched is to cover it with a protective mask - such as electrical tape

Gosh, that's clever and simple. I'll give that a shot!
posted by Blazecock Pileon at 4:38 AM on January 7, 2010

"Honing" is putting more teeth on the edge that you already have. If there is no edge to hone, you can not put more teeth on it.

You need to sharpen your edges before you can hone them.
posted by at the crossroads at 4:53 AM on January 7, 2010

Response by poster: No, honing is not "putting more teeth" on the edge.
posted by Blazecock Pileon at 5:27 AM on January 7, 2010

Blazecock is right, honing is what you do with a piece of steel, this device looks like it actually sharpens the knife. Here is a good knife maintenance resource, with a section on electric sharpeners towards the end.
posted by Dr Dracator at 5:28 AM on January 7, 2010

You need to sharpen your edges before you can hone them.

I'm not following your honing/sharpening/etc distinction. But I own a sharpener similar to what BP linked (I think mine is a previous model, but functions the same). I can assure you that if you use the coarse and medium slots it will grind metal away -- call it sharpening or whatever, that machine definitely does it. And then it has the fine slot which is more honing, if I'm following the distinctions above. No teeth are put on anything, though -- it's a straight edge.

Anyway, back to the original question, on mine I've never had blade scratching. It might have to do with how you were holding the knife? But if it is a problem, using masking tape (actually, I'd probably use that blue painter's tape, since it is so easy to remove) will probably do the trick, as was suggested. But before taping up all your knives, experiment with a cheap knife and see if the scratching has to do with your technique, rather than a design flaw.

About the cost: I think I paid about $100 for mine, some years ago. I've more than gotten that value back, even at $2 a blade (and I think that locally I'd pay more than that for sharpening, and the place doesn't even have a good reputation). So if you live down the street from a knife sharpening master who works cheap, that's obviously a better option. But if you don't, there are a lot of advantages to having the convenience of sharpening at home (as in, you can whip it out and do a quick touch-up even in the middle of cooking -- you'll never cut with a dull knife again).

I've read that skilled hand-sharpening is better, and I don't doubt it. Personally I'm willing to sacrifice a little perfection for the convenience; if my knives last twenty years instead of thirty or forty, I'm willing to pay that price.
posted by Forktine at 5:34 AM on January 7, 2010

Honing is not necessarily only straightening the edge. That's kitchen talk - what a "honing steel" does for you: fooling you into believing that your knife actually got really sharp again.

For true sharpening, one would use coarser grits of stones for re-grinding the general angle of the edge and successively finer grits for either shaping (honing, or polishing) the edge to perfection or (depending on the steel and the prospective use of the tool) for shaping and honing a secondary bevel. Ideally, with very carefully polished knife edges, the confusing phrase "more teeth" (in at the crossroad's post) would be as in: on the level of the metal's crystal structure.

Sharpness; an edge's need to be straightened as opposed to re-ground; and the degree of already achieved polishing of the edge can be checked with a good magnifying glass, and this is how one learns to improve one's technique.

Bench grinding, unless very carefully controlled (which is not what normally happens), tends to overheat and weaken the blade where you need it to stay toughest, and also tends to take away too much material at a time.
Water stones are tedious to use (and yes, some technique is needed, but it isn't too hard to learn) but provide safe results.

Bad water stones or stupid cheap supermarket blades are useless. You rub around for hours and nothing happens.

Electric knife sharpeners do indeed grind (and not merely straighten up the edge), but they never really polish the edge. The edge stays relatively rough. So in that sense, you do indeed end up with a set of microscopic teeth.
posted by Namlit at 5:46 AM on January 7, 2010

I don't know about the honing hoopla, but I got this little beauty for Christmas and my knives are super-sharp and in good shape.
posted by bunny hugger at 5:54 AM on January 7, 2010

Have you considered a manual v-sharpener? These devices range in price from $10.00 for a surprisingly effective pocket-size single stage sharpener, to 20.00-40.00 for nicer, multistage ones. Chef's Choice sharpers (both manual and electric) usually have an "angle control guide," and I think that may be what's scratching up the sides of your blade.
posted by drlith at 5:55 AM on January 7, 2010

I have the same ChefsChoice sharpener (ignore the nonsense about honing vs. sharpening; lots of people are trying to "teach" the OP things he clearly understands better than they do). I generally don't get scratches in my blades. Perhaps it's a technique issue? The technique is a bit finicky, and the directions should be followed precisely.

In principle, only the surface being ground/polished is in contact with the abrasives. If the scratches aren't on the cutting edge, you can use the electrical tape trick (sounds like a great idea) or try polishing out the scratches. If the scratches ARE on the cutting edge, perhaps there's some ceramic/metal bits stuck in the grinder/stropping disk? That could cause unexpected scratches.
posted by JMOZ at 6:03 AM on January 7, 2010

I have a similar electric sharpener, and it scratches the sides of knife blades (which, I think, is what the OP means). I don't think this is an issue of technique.

I eventually bought the same manual sharpener as bunny hugger, and can confirm that it puts a pretty good edge on knife without scratching the sides of the blade.
posted by paulg at 7:32 AM on January 7, 2010 [1 favorite]

I don't have a direct answer for your question, but I heartily concur with Dr Dracator's recommendation. It took practice, but learning the procedures in that article has paid off handsomely for me.
posted by Greg_Ace at 8:59 AM on January 7, 2010

For casual use, I have a sharpening steel. For serious sharpening, I use a stone, and have been happy with the results.
posted by theora55 at 9:59 AM on January 7, 2010

I have brought many crapily cared for knives (poorly cared for by their original owner) back from the dead using a Global Water Wheel Sharpener. The thing is crazy easy and the course ceramic wheel gets 'em back and the fine wheel makes them dangerously sharp. I've even used it on my Swiss Army knife with great results. Only takes a light touch as well, so no dangerous amounts of grinding away of metal.

The wheels only contact the edge, so no scratching of the blade either.
posted by qwip at 10:21 AM on January 7, 2010

I have the same sharpener that you linked to. It does a great job on our large and varied collection of high-end kitchen knives. The one thing that I would add is that there are specific instructions on how to use it including how you hold the knife, and what sequence you use to sharpen, hone, etc. I have not had any side-scratching problems when I have paid careful attention to resting the blade at the appropriate angle in the holder and used the machine as intended. All but one of our knives takes an extremely good edge on this machine. One of our knives flat out refuses to take an edge. I don't know what that means, but I would not hesitate to recommend this machine.

As to side scratches, if you want to tape both sides of the blade (I would recommend electrician's tape because it is thin and comes off easily) that might protect the knives, but learning to use the machine would probably be all you would need to do.
posted by Old Geezer at 11:57 AM on January 7, 2010

Personally, I take it to a pro, its worth having it done and rarely costs over $10 a blade. However you end up sharpening the blade, keep it clean and dry from now on. Leaving it wet in the sink will damage an edge far more than usage. Like wet razors, microscopic rust forms on the edge and dulls the knife.

I got a new chef's knife from Santa and threatened to hide it in my room if my roommates ever left it in the sink.
posted by MiltonRandKalman at 1:21 PM on January 7, 2010

Response by poster: For my last experience with a "pro", he charged me $30 for three knives and ended up taking off enough of the santoku's edge that it now almost goes right to the indentations.

I take pathologically good care of my steel, and my experience with the $2-per operation seems to be as bad as the $10-per operation, so that's the last time I hand them over to someone else.

My inability to get a good edge with a stone is why I'm looking into other options. Thanks to all who offered suggestions on manual sharpeners and other tricks.

I'm wondering about adhesive from the tape getting on the sides, but I'll be testing the tape option tonight. It sounds promising.
posted by Blazecock Pileon at 3:12 PM on January 7, 2010

Watch out for those sharpeners, they may take off too much material and you'll end up with a filet knife in a couple of years.

With respect to all the experts here, there are two things you do to a knife.

First, it is sharpened. This means using an abrasive to cut metal away to create the sharp V shape. Once it is sharpened, it is ready to go. (Honing is in the family of metal abrasion or shaping. Usually the final step after cutting the metal with a coarser stone.)

Anyway, depending on the type of steel your knife is made of, how well you care for it and what kinds of stuff you are cutting, and what kinds of surfaces you are cutting onto, this doesn't need to be done very often at all. And you don't want to do it any more often than necessary, because this material removal process removes part of the knife, and gets you up into the thicker part of the blade and makes the knife less fun to use.

So after it has been sharpened/ground/honed/whatever, you use one of those steels to true up the edge now and then. These do not remove any material, they just run along the edge of the blade and straighten it back out. Because through usage, the tiny thin little edge of the blade bends and gets all wobbly. The steel straightens it out.

The closest I have gotten to getting a good initial edge on a knife was using wet sandpaper mounted to a hunk of glass or marble. That got the edge nice and straight and it cut beautifully, but I still can't get the curved part of the blade right. I may have to build some sort of sliding clamp contraption...

Not that this helps the question directly, but I think it is good info to balance the answer out for posterity.
posted by gjc at 6:03 PM on January 7, 2010

Response by poster: So: Tape works. I tried packing and electrical varieties.

The packing tape was difficult to shape to the curve of the blade and was difficult to remove, but it was thinner than the electrical tape, so I thought I'd give it a try.

The electrical tape could be stretched to fit the blade's curve. But it was a bit thicker than packing tape and made it a bit harder to pull the knife through the sharpener. Also, adhesive from the electrical tape remained on the knife, but a bit of cleaning took it off.

I tried this out with my nice MAC santoku and got a nice sharp blade with no scratches. The tape was scuffed up at the tip of the blade, and more so on the left side, after pulling the knife through the right guide. Not sure if this is down to technique or the design of the grinder wheel.
posted by Blazecock Pileon at 5:30 AM on January 9, 2010

i'd have to agree with those who say to get it professionally sharpened. once a year would be plenty for a good blade. i'd recommend getting this victorinox chefs knife that lifehacker featured, the knife is amazing. as far as keeping them sharp, NEVER put them in the dishwasher and make sure the blade is always dried before putting it away. also, watch what surfaces you're cutting on. everything i've ever read online says that you blades will eventually get dull using the at home sharpeners.
posted by no bueno at 11:51 AM on January 9, 2010

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