How to sharpen a knife

This is a discussion on How to sharpen a knife within the Defensive Knives & Other Weapons forums, part of the Defensive Carry Discussions category; So i keep my knives pretty sharp, I have a smith diamond flat surface sharpener, and i also have a steel for honing. The point ...

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Thread: How to sharpen a knife

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    Member Array cheezewhiz6's Avatar
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    How to sharpen a knife

    So i keep my knives pretty sharp, I have a smith diamond flat surface sharpener, and i also have a steel for honing. The point is my buddys knives are always razor sharp, Sharp enough to shave hair. What is he doing? Maybe my technique is rusty. How do you sharpen your knives? Sharpeners? Technique? Thanks for the input.

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    Distinguished Member Array C9H13NO3's Avatar
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    I use a spyderco sharpmaker. Always comes out razor sharp. I can do freehand razor sharp, but it takes a lot more concentration. Key is consistant angle. A LOT easier to keep it consistant when you're using a sharpmaker since the blade is vertical and you can watch the angle easier.

    **edit**

    I was in a hurry and posted that. Anyway, some more detail.

    Consistant angle is the most important thing. a total 40 degree angle is about the best for knives. The edge also has to have some shape to it, depending on the grind. Most knives are hollow ground or flat ground, but they have a back bevel. This angle is slightly less than the edge angle. That helps keep the resistance down while cutting. On your edge, you are essentially bringing the two sides of the blade together, and forming a burr (a thin sliver of metal that curls over). Then you cut the burr off with another pass, and it's sharp. The more consistant your angle, the better the burr that forms, and the cleaner you will cut it off.

    If you're insistant on sharpening with a flat stone, you need to learn to gauge the angle. One way is to set the blade at the correct angle on the stone, put your finger on the stone, and slide it up to the spine of the blade. If you keep your finger on the same spot on the spine, you can use your finger as an angle guide. Eventually you'll learn to feel the angle, but it takes time. I think oversharpening is another common mistake. It doesn't usually take as many passes as you'd think. I've been sharpening on flat stones for a few years now (probably use them about two or three times a month), and then recently got a sharpmaker. I love the sharpmaker system. Takes the thinking out of it, and the learning curve isn't steep.
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    VIP Member Array ELCruisr's Avatar
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    You have to keep a constant angle while sharpening and then the angle you use is important as well.

    Also the grade of steel, it's abrasion resistance and hardness can effect the job as well. Some will bring up an edge fast, some take much more work, some really cheap steels never seem to take a decent edge.

    I cheat. I used to make them for a living and use my belt grinder and buffer. Takes less than a minute to get a razors edge. Of course there's years of practice as well.
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    Member Array Drail's Avatar
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    It takes most people a lot of practice to learn to really get a knife sharp of a bench stone. Practice on some old kitchen knives. Put a line of magic marker down the edge and watch how it wears off to see if you're maintaining a consistent angle. Use a good light so you can really see what you're doing. Another approach is the Lansky system. It will make it easy to get the same angle on every stroke. Read the instructions carefully. I use bench stones for my kitchen knives but for a really scary edge I use the Lansky.

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    Distinguished Member Array Chooie's Avatar
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    I use the lansky system but for the most part I don't use the guide anymore. I've found that I am quite capable of holding a 17 to 20 degree angle and can keep my blades hair shaving sharp. The only time I really bust out the guide anymore is to repair a nicked or flatted blade.

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    "Consistent angle is the most important thing."

    I agree...and any sharpening system that will keep that exact correct angle should do the job perfectly.

    Also if you are new to sharpening knives it's important to blacken the existing edge with a Sharpie marker so you can be certain that you are honing the edge correctly and completely.

    BTW: I use the Lansky Diamond sharpening system and it works great for me. I expect that the Diamond hones will last me forever so I'll probably never buy anything else though there are some great other options/systems out there.

    I also always finish up with a light stropping on leather impregnated with finest Jewelers Rouge.
    Since most of my knives are long blade length knives - I use a large piece of leather that has been "spray adhesive mounted" to a sheet of perfectly flat 1/2" thick plate glass.
    The stropping really only serves to brightly polish the already finely honed edge which a final step that I prefer.
    It's not absolutely necessary but, I think it keeps the edge a bit longer and the blade ends up so sharp that it actually scares the hair off before it even gets the chance to shave it.

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    I cheat!

    I take mine to my local knife shop. They put a razor edge on them for just a few bucks. If they screw it up (has never happened), I get a new knife for free.
    CCW permit holder for Idaho, Utah, Pennsylvania, Maine and New Hampshire. I can carry in your country but not my own.

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    Ex Member Array Ram Rod's Avatar
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    I used to try all kinds of different techniques with my pocket knives. Sticks and stones......etc. I'm more careful with the ones I have and what I use them for now mainly because I don't do well with knife sharpening, and if they get dull, I just get another to replace them. Of course none of my pocket knives are worth more than $30 new. I like a good pocket knife just about as much as a good ink pen. Several have lasted me many years, but over all, they are semi-disposable items to me which is why I sort of limit the initial cost.

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    I think it keeps the edge a bit longer and the blade ends up so sharp that it actually scares the hair off before it even gets the chance to shave it.
    Thats pretty sharp.
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    VIP Member Array LongRider's Avatar
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    Quote Originally Posted by cheezewhiz6 View Post
    my buddys knives are always razor sharp, Sharp enough to shave hair. What is he doing? Maybe my technique is rusty.
    It is probably the edge you have on yours. I like sharp knives and think a convex edge is the best for keeping a razor sharp working edge. It is easy to put one a new sharp knife and from than on you have a blade that will always be sharp requiring only an occasional stropping on a piece of leather or old belt with lapping compound of jeweler rouge . Below is a crude diagram I did showing how a convex edge looks. If you do not have new knife and are working on an older blade dull blade you may want to re-profile the edge to have about a 20 degree edge on it before convexing. When reprofiling you do not need to put a razor edge on the blade, just get it nice and sharp the convexing will put the razor edge on. I use a Gatco sharpening system to reprofile my blades.

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    VIP Member Array LongRider's Avatar
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    Convexing Directions

    I copied the below from CONVEX SHARPENING THE BRKCA WAY You can download Convex Sharpening PDF of it to print out and use when you start sharpening

    CONVEX SHARPENING THE BRKCA WAY

    By Reid Hyken aka: Sharpshooter

    Convex Sharpening PDF


    We’ve had a lot of conversations about how to sharpen a convex edge. I’ve found that a first hand demonstration usually is the best way to show how simple it really is. Perhaps a case of a picture being worth a thousand words, so let’s try with pictures.

    A convex edge isn’t what we have become accustomed to on cutting tools. What we usually see is a bevel, a flats ground on both sides of the blade creating a sharp edge.



    The convex edge is like a Bullet Point, gently curving to the edge.




    Most sharpening systems are made for the bevels that most manufacturers currently use, the idea being to hold a consistent predetermined angle along the length of the blade on both sides. That won’t work on a convex edge since there really isn’t a consistent predetermined angle on a convex edge, but rather a gentle curve. To do this with a stone, one would need to carefully “roll” the blade against the stone to follow the curve of the blade.

    There is an easier way, make the abrasive follow the natural curve of the blade. To accomplish this we need a flexible backing behind the abrasive.

    Sandpaper held tight over a hard mousepad or piece of leather glued to a hard backing such as a wood block.

    To refresh a slightly dulled edge one starts with 1500 grit paper and can work up to 2500 or finer. To resharpen a nicked or truly dull edge I start with 320 grit and work my way up, the same technique can be used to change a beveled edge to convex.

    Whatever grit you are starting with, the technique is the same.

    READ THESE INSTRUCTIONS FULLY BEFORE STARTING…

    The key to this is to pay attention to the contact between the edge and the abrasive.

    Lay the blade flat on the paper



    The spine of the knife is lifted slightly from the paper until the edge is contacting the paper; usually this is about a 13 angle. The angle isn’t as important as the contact on the edge; remember we have a flexible backing to follow the edge profile.





    Once we have this angle established, the blade is drawn across the abrasive, SPINE FIRST. We’re not trying to cut the paper, but to drag the edge across it, so we’re removing the material behind the edge not from the edge



    DO NOT apply much down force on the blade; the weight of the blade is sufficient to do the job. Press too hard and the abrasive will actually be coming back up in the wake of the blade and remove the edge, dulling the knife rather than sharpening it.

    As you draw the blade across the abrasive, you can feel and hear the abrasive doing the job. You’ll know it’s time to move to the next finer grit when the drag stops and the blade seems to move effortlessly across. The finer grits are removing the scratches left by the more coarse grit. We’re really polishing more than removing material, forming a wire on the edge and then removing it when we work the opposite side. This is a complicated way of saying that you need to work both sides of the blade.

    This would be the complete procedure were all blades to be straight across; it’s the curve or belly of the blade that trips a lot of people up.

    At first glance, one would think that they need to lift the handle as they follow the curve of the edge. That’s not correct… remember, we have the blade almost lying down on the abrasive and since the blade is flat the upsweep of the edge is not higher but at a different angle to the sharpening motion.

    The handle must be pivoted while maintaining the same plane to maintain the edge contact with the abrasive. In this picture, I have drawn a “Pivot Point” on the blade to illustrate this concept. In reality, I put my off hand index finger on the blade at this point and swing at that point. DON’T use the finger to apply down force it’s only there to provide a point of reference.



    The goal is to draw the edge across the abrasive at a perpendicular angle. Here is where a lot of people run into problems getting the tip sharp. Usually this is because they don’t continue to move the blade perpendicular to the abrasive, but rather draw the knife off the paper following the shape of the curve. A good way to prevent doing this is to keep in mind that blade is supposed to stay on the abrasive all the way across, the stroke ending at the far right or far left of the sheet, not the top or bottom.



    Once you have run the course of abrasive papers you have a sharp convex edge.

    To check that there are no more flat spots on the edge, I use a piece of hard plastic. They sell special rods of plastic to do this test, but markers work just as well and are plentiful/cheap. I put the edge against the plastic at about the same angle as I sharpened at and with no pressure run the entire edge along. Any flat spots will cause the edge to not bite into the plastic and skip off.



    Look closely at the picture and you can see how the edge is actually slicing the plastic, a flat spot will skip across.

    When you are satisfied that there are no more flat spots, you're ready to move on.

    You can further refine the edge by stropping it. To make a strop, 2 pieces of leather can be glued down to the wood block, smooth side up. Bark River Knife and Tool sells bars of stropping compound at a very reasonable price to finish off the job. The black compound is more coarse that the green.

    Heat up the leather until it’s warm to the touch and run the compound into the leather. I use a heat gun for more even heating. After I’ve applied the compound, I again heat the leather to work the compound in. Using the same technique as on the abrasive paper, strop the blade, several strokes on the black followed by the green.



    Once you have the edge good and sharp, you really only need to strop it to keep it keen, saving the abrasive paper for when the edge is nicked or if you get it really dull.

    There are many ways of seeing how sharp and even an edge is, one I use is slicing paper. The thinner the paper, the sharper the knife must be. Here's a couple of fine curls made by the NorthStar I sharpened for this article on some this white paper, after passing it around to ten or so people over a weekend to try it out, the edge was pretty rough. Now you can see that it makes some very fine curls in the paper.



    It only takes a few seconds to get the edge back to hair popping if you get in the habit of stropping after a day’s work.

    Feel free to link to this article so long as you credit the Bark River Knife Collector’s Association. Reprinting for distribution or publication requires permission, please contact the Webmaster for permission.

    Reid T. Hyken 2006
    Hope that helps. It should give you the hungry blade that QKShooter has be careful who you hand your knife to people have a tendency to cut themselves with knives this sharp
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    Senior Member Array Scot Van's Avatar
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    This goes to show how many different ways there are of doing something. I was a chef for quite a while, and I always used a Norton Tri-Stone. Most Henkle and Wustof dealers have the Toledo Triple, but I think the Norton is superior.

    Also, instead of moving the knife AWAY from the edge, I was taught to sharpen kitchen knives by pushing the blade in the direction of the cut. This works well, and probably is NOT the technique you would use to get that nice convex blade beautifully illustrated by Long Rider in the above pictorial. The hone of the blade, once sharp, is maintained with a steel, not a strop, and the knife passes over the traditional steel in the same fashion...towards the blade.

    http://www.ehow.com/video_2346178_sharpen-knife.html

    This guy may seem a little flakey, but he's doing what I mentioned (with a crappy stone and a crappier knife).

    Nothing I've ever used in a kitchen justifies that kind of time and effort required in obtaining and maintaing a convex edge. I use knives that, though not custom, are recognized as some of the finest knives in the culinary arts classification, but working with a chef's knife is work...to use convex edges, you'd be sharpening your knives (lovingly, to be sure) all darned day. For a skinning or carry knife that is a point of pride, the convex blade is as beautiful as the knife itself. For a utilitarian item that is used to chop onions and celery AND hack apart bone and gristle, it is my feeling that nothing is easier or better than this technique with a Norton Tri-Stone. They're pricey, but worth every penny.

    An old saying in the kitchen...the only thing more dangerous than a sharp knife is a dull one.

    Good luck!
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  14. #13
    VIP Member Array LongRider's Avatar
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    Quote Originally Posted by Scot Van View Post
    An old saying in the kitchen...the only thing more dangerous than a sharp knife is a dull one.

    Good luck!
    Van I cook as well and did so for a few years in some fairly decent restaurants. Try convexing one of your Henkles you will love the result. It holds a razor edge much longer I can go from splitting chickens to slicing tomatoes with mine. Wash the knife between the chicken and tomatoes of course. The convex edge is the perfect companion to good quality steel like Henkle. Just change our way of doing things rather than the steel just strop your blade a few times. The difference is you will need to do it far less often and the result is a sharper longer lasting edge. That is one of the advantages of a convex edge it requires far less to maintain than a scandi (flat grind). Knife maker Ethan Becker designer of the Becker Brute currently of KA-Bar/Becker makes excellent survival knifes. He is also author of The Joy Of Cooking and a convex blade fan. Just to pricey to do with production knives.

    Convexing a blade can be tedious. The better the steel the more time consuming. But once it is done, it is easy to maintain. Barring serious abuse your knife need never see a stone again

    What we put our camp knives through is far more brutal than what we do with our kitchen knives at least I do not skin and butcher game, chop the wood for the fire with my Henkles before I use it to prep dinner as I do with my camp knives.

    Anyway give it a try you may like the result.
    Stay sharp
    Last edited by LongRider; January 12th, 2009 at 01:17 AM.
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    BJC
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    I use the Spyderco system. Quick and easy and works great.

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    Learned a lot with my sharpmaker today. I was rebeveling one of my benchmades and found out why I couldn't get it sharp as I wanted on the sharpmaker. Used a sharpie this time, found out the left side, where I can view the angle on a bench stone I had been stoning for about a 42 degree bevel, (so the sharpmaker was hitting the shoulder and not the edge), and the right side (where I have to go by feel on a benchstone) I was angling for about 32 degree bevel. Sharpie will teach a lot about what you're doing. That blade needed a rebevel though. I've had it for years now, and it was just starting to wear down quite a bit.
    -Ryan

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