Knife Sharpening Tricks

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About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of www.zcorp.com, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific...
There are many ways to sharpen a knife. This method produces a good general purpose edge.

Safety note: As my Granddad used to say: "Don't cut toward yourself, and you'll never get cut."

Excellent photos by Christy Canida the whale butcher.
See what she does with these knives at Skinning and Filleting Catfish

People have always cared about sharp tools. Some "Bog Man" remains from thousands of years ago have been found with sharpening stones worn as a pendant.

This first video shows how to make your own Bog Man stone from a regular sharpening stone, or any soft abrasive stone you happen to find.

First we will make a drill bit from a nail, drill a hole in the stone, saw the stone in half, and flatten it. Just like an ancient bog man would have if he had the battery drill we fixed last week.


This second video shows how to sharpen a knife for butchering and how to sharpen it for carving wood. I bought the knife in the video from a husband-and-wife team of blacksmiths in China. Blacksmithing seems to be a job for couples in many parts of the world.


Links to the ipod formated videos are at the bottom of this page.

Step 1: Look at the Edge

Get under a bright light such as the sun, and hold up the edge. You'll see reflections on flat spots and nicks.
On this blade the inch near the tip is pretty bad.

Step 2: Thumbnail Test the Edge

Touch it to your thumbnail and see if it slides around or if it catches.
If it slides that means it's dull, as in not sharp, at least in this area.
Safety note: Don't chop your fricking thumb off.

Step 3: Flatten the Stone

Buy yourself a sharpening stone for a dollar in Chinatown. If your city doesn't have a Chinatown, get one or move somewhere civilized.

This is a "water stone" which means you put water on it while using it to float the sharpening dust off it. Some prefer an "oil stone" which means you put oil on it. Some stones are born oily. Once the oil is in there water doesn't work well anymore.

This particular stone has had some use so it's dished out in the middle. That makes it hard to hold the knife at the right angle. So we'll need to flatten it.
Actually it doesn't really matter for knives, but when you start sharpening plane blades you'll make a religion of flattening your stone.

Step 4: Flatten Away

Splash some water on the sidewalk and rub the stone on it til the stone is flat. Use plenty of pressure.
Listen to "The Great War for Civilization" by Robert Fisk while you work to understand what went wrong in the Middle East.

Step 5: Thin the Edge

Rub the knife on the coarse side of the stone at a 5 degree angle as shown. It doesn't matter what stroke you use or what direction.
You're just thinning the area around the edge a bit to save you some labor later on.
In each of the following sharpening steps, you'll raise the angle just a bit.
That way you're always shaving the stone with fresh metal.

Commentators to this howto are rightly pointing out the merits of a 20 degree knife edge, (knife held at a 10 degree angle to the sharpening stone) or a 17.5 degree wedge. I think my homemade plane blade sharpening fixture is set at 27.5 or something nerdy like that.
Use your own numbers, not mine, and by all means get carried away with your own refinements.
The numbers I picked aren't too important, just that you raise them with each step.

Step 6: The Sharpening Finally Begins

Flip the stone over and stroke the blade edge forward at a 6 degree angle. First one side of the knife, then the other. You are cutting toward the stone.

Step 7: Gilding the Lily

You've already endangered your friends by putting on an edge on a knife they're expecting to be dull.
Now it's going to get even sharper. Get a piece of 600 grit emery paper and put it on a piece of glass.
Any other really flat thing will do, but glass is most popular. I've seen Klingit and Mayan woodcarvers use this method.
Stroke forward at a 7 degree angle, alternating sides. A couple of strokes is plenty, because you're taking off a miniscule amount of metal. If you're silly or special you could get finer grits up to 1200 and repeat.

Hats off to the commentators for true facts about edge angles. Unless you're into artillery in a big way, most of us will overestimate small angles. Your 7 will be more like 12 in reality. The important thing is to look at the edge, test it, and raise the angle til you're shaving just a little abrasive off with each step. Thick blades will naturally sharpen at the higher angles they were intended for. You'll never really thin a thick blade out that much.

Some things like plane irons and chisels benefit from a straight bevel. For that make a jig to set the angle. Plane irons seem to inspire the greatest nerdiness in people.

Step 8: Cut Your Leg Off

Not.
This step is a totally unnecessary way to show off. You can impress people this way, especially if you rip your leg open, blood gushes everywhere, and they have to take you to the hospital.

Smear your leg with the abrasive paste you made by flattening your stone.
Then stroke the knife over this paste, sharp edge trailing.
This is called "Stropping". It takes the microscopic hairs off the edge to make it strong and extra sharp.
This is how you sharpen a razor, except sane people use a piece of leather called a "strop" rubbed with red garnet abrasive dust.

My Granddad used to beat his kids with his strop when they misbehaved. His son, my uncle "Bird Dog" tried to shave without proper instruction and cut a big gash in the strop. In the ensuing punishment the new sharp corner cut him, he started bleeding all over, and my Grandmother Nana came flying out of the house with strong new theories about corporal punishment. She was half my Granddad's size and twice as powerful. The kids were able to eat dinner sitting down for a while after that.

Step 9: Don Montague Tests the Edge

His style of fingernail testing involves resting the edge on his nail to see if it slides off or catches.

Step 10: Improvised Sharpening Stones

There you are in your friend's kitchen trying to cut a tomato with a blunt knife.
You're mashing it and smearing the skin around and not feeling sexy at all.
You ransack the utensil drawer and find not an abrasive.
You get the urge to criticize your pal for being the wrong kind of tool-using ape.
Halt.
Use an improvised stone instead. Here's a short list of what can work:

The underside of the toilet tank lid.
The rough unglazed ring on the bottom of a plate or other ceramic item.
an emery board used for manicures
A brick.
A flowerpot.
Any aluminum item. It's covered with a layer of aluminum oxide, a good abrasive. This method is only good for final sharpening.

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    247 Discussions

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    coryj25

    2 months ago

    Another good surface to use to hone an edge is the top side of a car window. Just roll it down so you can run the knife edge over it. Also loved this tutorial.

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    Sharpest32

    1 year ago

    Nice post, and I like how it's well detailed. Another cool way to "true" or flatten a stone is by using a DMT (Diamond) stone to grind your traditional stone.

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    1259700020

    1 year ago

    I personally use a low end tri hone set up and can get an edge shaving sharp on the medium stone and have yet to have fully utilized the fine grit stone (it is so fine it feels smooth to the touch).

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    LindaKayG

    2 years ago

    your casual and humorist is very empowering I'm going sharpen my own knives. IM GOING TO DO IT!!

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    volkvanmyn25

    2 years ago

    I'm using a Lansky sharpening system to reprofile my blades and Spiderco Triangle sharpmaker to finish off the edge to give hair splitting sharpness

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    Laral

    2 years ago

    I have to laugh about your comment implying that a city with a Chinatown is somehow more civilized. Any Chinatown I've ever been to in this country is the epitome of barbarism. Rude shop and restaurant people, rotting food smells all around, sidewalks 8 deep with throngs of people. Shady-looking people on the sidewalks. My Chinese wife feels the same way. We visit Flushing fairly often and there is (some) good food to be had there but that's about it. The only Chinatown we have ever been to that is an exception is the one in Toronto. It is clean and spacious and respectable. The exact opposite of the American variation. Where we live now, there are Asian stores so no Chinatown necessary. Chinese stones are crap IMO. They are of inferior material and 'bow' rapidly. I think the sidewalk idea could net you a fine if you're caught. A cheap square of tile would do the same thing. As for sharpening by hand, it takes years of practice to get good at it. The Lanksy sharpening system is what I use. It keeps the stone at the proper angle(s). My stones are still flat after decades of use. They are high quality stones.

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    Magzzee

    2 years ago

    Fabulous ible and even "fabulouser" humour, you're NUTS (but in the nicest possible way!!) TYSM for the laughs and great instructions. Looking fwd to seeing more of your stuff.

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    shellyscorner

    2 years ago

    Well done! I really enjoyed the tongue in cheek humor. Especially the story about your grandfather! Don't you love old family stories!?! I'm a BIG believer in spanking. But spanking with your hand is as far as you get to go, you don't get to leave marks, bruised and such, and you NEVER EVER spank while your angry! THAT'S when things get out of control! It's also where the phrase, this is gonna hurt me more than it's gonna hurt you!" comes from. Much harder to spank a child when your not angry!

    Anyway, I digress.... The idea of running a knife down my fingernail makes me a bit nervous! But I might just have to try that. Definitely not an expert with knives, not sharpening them anyway, although I do sharpen my regularly, I question how well I do it. Again, well done and I enjoyed it.

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    shellyscorner

    2 years ago

    Well done! I really enjoyed the tongue in cheek humor. Especially the story about your grandfather! Don't you love old family stories!?! I'm a BIG believer in spanking. But spanking with your hand is as far as you get to go, you don't get to leave marks, bruised and such, and you NEVER EVER spank while your angry! THAT'S when things get out of control! It's also where the phrase, this is gonna hurt me more than it's gonna hurt you!" comes from. Much harder to spank a child when your not angry!

    Anyway, I digress.... The idea of running a knife down my fingernail makes me a bit nervous! But I might just have to try that. Definitely not an expert with knives, not sharpening them anyway, although I do sharpen my regularly, I question how well I do it. Again, well done and I enjoyed it.

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    VladM3

    2 years ago

    Yes! Great humor!

    I would advocate for finer sharpening. Up to 4000 grit is good for me. I go 600, 1200, 4000. If you spent a whole day butchering animals you would want to sharpen that well. The edge lasts longer, cuts faster, and you can do fancier cuts without cosmetically ruining the meat. Some of my relatives scoffed at me for taking the extra few minutes to sharpen, but once I got them to try it I couldn't get my sharpening stones back.

    And remember...sharpen often. A sharp knife is dangerous, but a dull knife is unpredictably dangerous.

    2 replies
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    big-jamieVladM3

    Reply 2 years ago

    Its not until you've used a properly sharpened knife that you realise what crap youve been trying to cut with. I started making knives, and sharpening my own when i lived with my parents so every now and again i'd sharpen my mums everyday use knives. and when i moved out i urged her to, even once a week, just give them a quick 5 min sharpen, but no, 3 months later im visiting and her knives are so dull you can drag your finger down the blade with no risk of a cut and shes complaining potatoes slip out her hand and chicken just 'mashes' when shes trying to cut them. So cue me spending 2-3 hours sharpening all her knives, buying her a knife steel, and teaching her how to care for her knives properly. She now has the audacity to complain about my knives being dull when she comes for a visit haha (my knives are never dull, its just a running joke).

    So yeah, whole point of this is people really dont know what their missing until they actually sharpen their knives and then generally never go back. One proper sharpening of your blade and a few flicks of a knife steel before you cut something you wont need to resharpen using stones for upto a month (depending how much you use it, and depending on your chopping board too actually. Plastic and wood are much better for knife edges than glass or stone.)

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    shellyscornerbig-jamie

    Reply 2 years ago

    I SOOOOO agree with you! I LOVE a sharp knife in my kitchen!

    My brother makes knives that are unbelievable! And no, I'm not just biased. I AM VERY proud of him though! He has a degree in mechanical design and has made some extremely impressive things over the years! He has multiple videos on YouTube about his knives. You might be interested in watching, just for fun. . . He's well known for his durability demonstrations where he "cuts" through cinder block with his knife .... to show that the blade won't break .... Check him out. Search for "NateAIM" on YT, I think you'll get a kick out of it. He makes field knives as well as kitchen knives.

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    Hassocker

    2 years ago

    Do you have a link to the Blacksmiths in China please? I could do with some new knives.

    1 reply
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    shellyscornerHassocker

    Reply 2 years ago

    @Hassocker - Hi! Check out NateAIM on YouTube. He makes knives that are virtually indestructible! AND he stands by them. THEY ARE NOT CHEAP ..... BUT THEY ARE PHENOMENAL! https://www.youtube.com/watch?v=1w1_WX_fNN8

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    maxman

    2 years ago

    Get a belt sander like I just posted about. You wont regret it. Don't mess with anything else.

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    maxman

    2 years ago

    I bought a belt sander from Harbor Freight and a leather belt to fit it somewhere online. Then I loaded the belt with green polishing compound. After stoning a knife I strop it on the belt sander. It makes the sharpest knives I've ever seen. I can shave with my pocketknife.

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    shermanduke

    2 years ago

    I go all the way to a 6000 grit water stone.

    I just push down on meat. No slicing needed.

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    plasticbaldy

    2 years ago

    Love the humor. Thanks.

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    StepsS

    2 years ago

    I grew up in a olds school barber shop.. German gold inlaid cut throat razors, ans a father who also hunted and filleted meat fish etc

    The biggest thing to a sharp knife is storage.. NEVER in a draw, and never draw across a bone when filleting or carving. Select the right hardness blade for the use. The sharpness of the edge depends on the use.. no need for a stropped cut throat razor edge (if possible ) on a kitchen knife cutting tomatoes .....dont expect a good and lasting edger out of crap steell

    Angle depends on a combination of 3 things

    1/ the hardness of the blade...harder the steel the finer one can hone the blade and keep an edge

    2/The use of the knife...in the kitchen or cutting baits out fishing. Harder the item cutting steeper the angle.

    3/ The alloy.. high carbon steel doesnt chip, high carbon stainless knives tend to drop the carbon crystals out of the edge resulting in very fine and sharp saw edges.

    To sharpen.. work the blade on the hone at the required angle determined by the above to get an even reflected working edge each side and remove any chips. Working a fine burr each side. Move to finer stones as required and lighter pressure.. each time forming a very fine burr.. till one is using just the weight of the knife....

    Things like axes or machetes where chopping takes place.. one edge will be wider than the other depending if the user is left or right handed.. stops the blade glancing off on a angle chop.

    For softer blades, a final very light wipe on the stone at a steeper angle will help to maintain the edge longer.

    A steel or ceramic edge doesnt sharpen, it just re forms the microscopic edge burr on good steel alloys..and will not need to be re honed on a stone for a long time if used , and stored well.

    Sharpening tools is not rocket science, just a little practice, bit of thought and commonsence

    The best 'definition ' of a sharp (kitchen) knife, is will cut 1/2 way thru a tomato under the weight of the knife only, when drawn across.. think was Julia Child who said that.

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    oaking

    2 years ago

    Very nice article, thanks for the added humor.

    Sharoening tends to be very personal.