What is sharpening a knife about? (2015 updates!)

Thanks for bumping this, it was a good read and deserves more readers. Good job, Magnamious_G.
 
Great detailed explanation of the term/concepts! Thanks for taking the time and great info :thumbup:
 
I also like my Arkansas stones. I managed to locate a stone cutting company that cut the stones in house. I came away from there heavily loaded with quality stones. My favorite is an extremely hard stone , almost like glass.If I really take my time and work up to it slowly (coarser stones first) I get a scary sharp edge. These are large 10-12 inch long by 2-3 inch wide stones. Wouldn't part with them for anything.



kevnkar said:
Nice write up for sure. That being said, when I was a kid, there where two options, low tech being carborundum and high tech being Arkansas stones. There was no internet, no diamond stones and ceramic rods where just thinking about coming out. No one taught me to hone an edge. I spent hours with Arkansas stones until I could pop hairs off of my arm. I guess the point is, just go and sharpen your knife. Create the edge that works for you without spending an arm and a leg. People used rocks for thousands of years with great results.
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wonderful article to set new/rookie sharpeners on the correct path. me being one of them; i was thinking that this post should have a video clip should come with it. :thumbup:

am i trying to get you to make a bare bones dvd on the subject? hmmm maybe i am, i can see a nitch for such a thing cause all newbies really need something like this to get there feet wet imho. dreams sometimes come true. thanks for sharing your knowledge and time with us sir. Namaste
 
Thanks for the in-depth writeup. It's good to know the how and the why, especially for another beginner like myself. So far I've collected a number of various stones, hones, and even made my own strop, but have been waiting for the most important tool, the knowledge, before I continue down the path of experience. I think I'm ready to start now!
 
great write up and very helpful. My dad, who passed away about 7 years ago was so good at sharpening knives. I used to watch him and he would show me how to do it when I was younger but never was able to get an edge like he did. He has been sharpening things his whole life for work and at home. its true that practice does make perfect. He just knew the exact angle for the particular knife and had that steady even hand and made it look so easy. He did not have fancy equipment, in fact I have the stone he used and its at least 50 years old if not older. One side is coarse and the other side is fine.
Hopefully someday I can get to that level and this article is helpful. thanks
 
Thanks for taking the time to provide an exceptionally clear and well written description. I'm a new member and this kind of information is exactly what drew me here.
 
Magnaminous_G said:
What is sharpening a knife really about?

What is sharpening a knife really about? Simply put, it's about forming a clean, new edge (i.e., apexing the edge and removing the burr). When I first tried my hand at freehand sharpening, I would work on the stones forever, going all the way up to the Spyderco Ultrafine bench stone until the bevel would be polished like a mirror. I’d look at it in the light and be very proud. Wow, did it glimmer! Then I'd try to cut a piece of heavy stock copy paper (which, by the way, is the easiest paper to cut)... and the edge wouldn't cut it… my mirror-polished bevel was duller than my Ikea butter knives. And I got so frustrated, I’d want to cry. It took quite a while for me to understand what was going on between the stone and the edge. Fundamentally, I didn't understand that there were things I should have been watching for… carefully… like a hawk. I thought it was a math game: "5 strokes this direction, 5 strokes this direction... whew... I’ve been at this for a while, so I guess it’s time to move to the next stone." To the contrary, moving on to the next stone is about knowing *when* to do it. (explained below in the section "How do you know how long to sharpen and when to move to the next stone?")


Refinement vs. Sharpness

Sharpness does not equal refinement. They are not the same thing, at all. In fact, they are two different things. Related, but different. You can get a push-cutting edge on a DMT coarse stone if the edge is apexed and the burr removed. The bevel will look like you took an old rusty file from grandpa’s shop and attacked your knife… but it will push cut paper. Why? Again, because sharpness is not about refinement. It’s about apexing the edge and removing the burr. So what is refinement? Refinement is about making that apexed edge smoother and less toothy, but it doesn’t really affect sharpness. So why do we refine an edge? Why not just finish on one coarse stone? The reason why is because the coarse stone leaves an extremely toothy and jagged edge which will deform easily and dull quickly. People refine edges to get a cleaner, smoother, longer-lasting cutting edge. The extreme example would be a straight razor polished by a honemeister. You see, even though you can get a scary sharp edge off of a 1k stone, it won’t shave smoothly (i.e., it will irritate your face). You need to go to 16k, or 30k, or JNats, or Belgium Coticules to smooth that edge out to the point it’s like glass and doesn’t irritate the skin. That’s refinement. Not sharpness.


So what degree of sharpness and refinement should I be going for?

So what degree of sharpness and refinement do you need? You *always* need the ultimate in sharpness: a fully apexed edge that is burr free. What degree of refinement do you need? It depends on how you use your knife. For most kitchen knive and pocket knives, the degree of refinement that is ideal is probably between the two extreme examples above (DMT Coarse and 30K water stone)… maybe 2 – 10K. You can achieve this with two stones: something “Medium” and “Fine,” although those are not exact terms and will vary among sharpening mediums and brands. Most people who are hobbyist sharpeners (like me) have added coarser stones (for quick reprofiling and edge correction) and finer stones (for greater refinement). Professional sharpeners may have many, many more. Then again, many professional sharpeners only use two cheap stones. I know that Murray Carter only uses a 1k and 6k King stone, for example, and he has been sharpening professionally for twenty years (although he has a large powered stone wheel for bevel setting and reprofiling work).


Newbie sharpening mistakes explained

Okay, so in real terms, I think these are the most common mistakes of new sharpeners:

A) didn't spend enough time with the coarse stone establishing the bevel and correcting problems
B) didn't check the edge often enough
C) didn't know *what* to check for
D) didn't understand that the final stone is for cleaning that edge up to the maximum (the mirror bevel is just a side-effect, not the goal).

I would wager that, under magnification, most new sharpener edges done freehand have lots of uneven lines from inconsistent angles on the stones (which takes practice to be able to achieve a consistent angle with each stroke). Also, the edge bevel probably isn’t even (especially at the tip and/or heel of the edge), and the scratch pattern isn’t fully established (and the edge isn’t apexed fully). And I would wager that this is because they were making it a math game and weren’t really sure when to move to the next stone. It’s not about a certain number of strokes on one side or the other. It’s about when the scratch pattern is fully established (transferred from the stone onto the bevel, like an imprint), all the way to the edge, until spending more time on that stone would be a waste of time as one wouldn’t be changing anything but rather only removing more metal needlessly. So the thing to know is *when* that has happened and thus *when* to move to the next stone. And that's the topic of the next section:


How do you know how long to sharpen and when to move to the next stone?

The way to know how long to sharpen and when to move to the next stone is by concentrating on keeping a consistent angle with your first (coarsest) stone and not being afraid to work that stone. You won't hurt your knife. Work that bevel until it's one even, clean scratch pattern from tip to heel. This can be *very* difficult to see if you are new to sharpening, so I highly recommend investing in a 10X or 15X loupe. I prefer Peak brand. There are others. This will let you really see what your edge looks like. But even with the naked eye, if you look really close, you should see if you’re making an even bevel from tip to heel with no areas of that bevel that don’t look like the rest of the bevel (this is usually the case near the heel and near the tip for new sharpeners and for factory knives that have never been sharpened).

It will probably be slow-going for the first few sharpening sessions, too, because it takes time to get comfortable holding the knife correctly and establishing the motions, which are not natural to most people. And regardless of your sharpening skill level, you will always have to spend time with that first stone. In fact, in my humble opinion, 80 - 90% of the work of sharpening is on that first stone because you are correcting problems and establishing an even scratch pattern. The higher grit stones are only used to remove that coarse scratch pattern on your now perfect bevels and then replace it with the higher grit scratch pattern. Then you move on to the next stone and repeat until you are finished with the highest grit stone.


Burrs!

Burrs: to establish or not to? Here’s the dirty secret: you will always establish a burr if you are sharpening correctly. Even if you are using a Sharpmaker and dutifully stroking once on each side, from one side to the other and back again, you will work up a burr as each stroke works that bevel and creeps to the edge. It’s just so small and thin you can’t see it or feel it. When people say, “You need to work up a burr,” they mean really work up a BIG burr that you can easily feel with your finger. You do that by working one side a lot. Then that big burr gets raised. And the reason why they tell you to do that is because this is a good way to know that you have indeed apexed that side. But how much of a burr you work up isn’t important. You just need to have worked that side until you’ve scratched the whole bevel to the edge. The burr is just a side effect of doing that, and yes, it is a good reference for a new sharpener. Okay… so let's say you've done that. And then you do the other side, carefully keeping an even angle and working the whole bevel from heel to tip and completely replacing it with that particular stone’s unique scratch pattern. Okay. What happens then? Let’s talk about results…


Finalizing the edge and getting results

Then you try to cut a piece of paper, and whoa! It cuts! But it’s rough… it catches in places. It tears the paper in places. Why? Because there’s still bits of burr on that edge. So you have to get rid of them. There are several ways to do this. Some highly-respected sharpeners (Murray Carter, for example), drag the edge ever so carefully and lightly, with a feather-light touch, through a piece of soft wood, cork, or hard felt. That will do it. I think a much more advanced and elegant way is the knifenut way: a progression of careful edge-trailing strokes, first with firm pressure and gradually lightening until you are just “kissing” the stone. The abrasiveness of the stone will “pull” off those remaining bits of burr as you drag the edge backwards across the stone.

Then you try to cut a piece of paper again, and WHOA! It slices cleanly. It doesn’t catch in any places any more. Now you’ve got an apexed, burr-free edge.

If you are not getting those results, do not despair. Practice makes perfect.


How high can/should you go in grit?

So when should you stop? How high of a grit do you need? What compounds should you use to strop? Or should you just strop on newspaper, jeans, bare leather, etc.? That depends on what you plan to do with your knife. Need to put an edge on a kitchen knife? 6K is all you need. That’s refined enough to last and toothy enough to cut tomatoes effortlessly. Need to shave? 12K or higher, and preferably even higher (30K, or very fine Jnats or Coticules). A straight razor's edge needs to be smooth enough not to irritate skin. Need an edge for a sodbuster or any hard use pocket knife? I don’t know, but I suspect 1Kor 2k, done well, will be all you need. So what about the sub-micron sprays on balsa wood and the resulting edges that make feather sticks out of hair? Sure, go that route… if you need to make feather sticks out of hair. Again, how refined the edge needs to be is dependent on how you plan to use the knife, but you should always, *always* have a fully apexed, burr-free edge that is truly sharp. That is what sharpening is about.

And anyone can do it. It just takes practice.

- Mag
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This is a really useful and informative write-up! As a beginner(besides learning as a kid in boyscouts) I am grateful to have all this wealth of information at my fingertips. I'm wondering if you could post any pics of the process, particularly of Burr formation and removal, evenly scratching the bevel etc. Or maybe you have some good links to photos/vids already out on the interwebs you could direct folks to. Thanks!
 
I just picked up a Spyderco Sharpmaker and man o man was this helpful.
Absolutely spot on with what I was doing wrong. Not spending enough time on the course rods. I went back and used this guide and made sure the scratch pattern was fully laid down before moving on to the fine rods.

Got MUCH better results after reading this.
Thanks a bunch.
 
rdmyofb said:
My favorite is an extremely hard stone , almost like glass.If I really take my time and work up to it slowly (coarser stones first) I get a scary sharp edge.
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Sounds like you got your hands on what once was known as a Hard Arkansas Black. The surface resembles glass and it will refine an already sharpened knife into a truly superb edge. They used to be "oilstones", to be used only with a thin coating of oil. I used mine that way for decades before trying them with water (works okay), then with a squirt of dishwashing liquid and a few drops of water (works better). It was always such a mess with oil that I moved away from the black Arkansas stones until I tried the detergent method. Now they (I have three of them) are back in my regular routine as the final step before knives are returned to the kitchen.

BTW, Mag, great summary.
 
That was an incredibly useful article; well written and very informative. It helped me figure out a couple things that I could be doing better, and it worked wonders on my EDC knife. Thanks!
 
To Magnanimous, excellent post. Everything in there seemed accurate to me, well put and understandable. Also, and mainly, it was short enough that it didn't get boring. Everything you said hit on an important issue. No wasted words. My thanks for posting it. I like to save written stuff that I like and yours will be saved.

One area I would like to comment on. Burr removal. I'll try to be to the point like you did Mag. I tend to ramble. From here on I'll state what is my opinion. Not necessarilly fact. In the past what was my opinion changed as a result of more education and experience. I see no indication this will change. So,,, When I sharpen my GOAL is to NEVER CREATE A BURR. As you said Mag, this is impossible. But with my goal being perfection if I fall slightly shy of it the results will be better than if I shoot for "almost" no burr. That's just a personal way to look at it. Since there will always be a burr, what to do about it becomes critical. My main problem is the theory of "straightening" the edge, usually with a steel. I'm talking about the process of taking a burr (big or little) and folding it out straight. Another theory is that you can completely roll the burr over to the other side. I don't know if it rolls or if you removed the first one and created a new burr with new steel. It's not important. Both of these theories need to be re-thought. Why? Not because of haveing a sharp edge when you are finished sharpening. The issue is edge retention. A burr that has been "straightened" or folded out straight will feel very sharp and cut news print or phone book paper nicely. But when you start using the knife, especially if you are cutting tougher stuff like cardboard, these burrs that have been folded out straight will snap off leaving the edge degraded. This can happen very quickly. Not only will your knife not cut as well as it should or did 5 minutes ago, you may think the high quality blade steel you spent serious money on actually has poor edge retention. The problem may not be low quality steel or poor heat treat. It may be the condition of the edge when you start using it. Just a thought to think about. :)

There is one sure way to be sure you DO NOT fold a burr out straight. That is to only use leading or push strokes. If you are contacting the stone with the edge apex you will ALWAYS remove the burr. You won't MOVE it to the front of your edge. You still need to deal with NOT creating a new burr on the opposite side of the edge. This possibility is reduced by using very light pressure. Enough pressure to GRIND THE BURR DOWN to the edge apex but not enough pressure to form a new burr on the other side of the edge. Or, a very very small burr at the worst. OTOH, if you use trailing strokes, even with very light pressure there is a CHANCE a burr can be folded straight. The key here is to use pressure that is light enough to GRIND the burr DOWN to the edge apex before the weakened steel is folded. I forgot to mention that the burr is very weak steel compared to the steel that is still inside the blade. It's weaker also than the steel that is exposed but has been well sharpened leaving the bevels meeting each other with no burr. Magnesium already said that. I won't say there is only one way to effectively remove a burr or that I use the best method. But, everyone (IMO) needs to think through the process of removing a burr. Listen to lots of opinions. Figure out what makes sense. Finally try the one or two that make the most sense to you. My guess is that if you have a knife with a blade steel that is known for having good edge retention and the knife came from a manufacturer or maker who has a good reputation for good heat treating and the knife is getting dull faster than you think it should the problem may be in the edge condition after being sharpened.

I've been working hard at improving my sharpening skills for about 5 years. I've improved a lot. I've also believed in my heart a lot of things that I now know are false. But I'm also getting better edge retention from any knife I use with any blade steel I use than I used to get. I believe in my heart it's because of my improvement in ability. I'll take this opportunity to thank everyone who has helped me with advice. Even the "not so good" advice because I know it came with good intentions.

Back to the point. How do you decide what you will do about removing burrs? Consider the options. 1) Slide edge across the corner of a board. 2) Use a trailing or stropping stroke to remove it. I think these two are the most popular. I've heard lots of people say they strop only to remove burrs. While this is true to an extent I prefer to reserve stropping for improving an edge that is already burrless (as possible). I choose to remove burrs using only stones. This has taken me a lot of practice. Especially in the past year. I am retired so I have time to sit in front of the tv and sharpen for as long as I want to sometimes. One of the things I used to believe with all my heart is you absolutely need to strop to get a really sharp edge. I have tried different leathers, balsa, abrasives, expensive sprays, etc. The theory of needing a strop to attain a sharp edge was challenged with intellegance a few months ago. So I put my strops away and only used stones. I replaced the stropping with learning how to apply ultra-light pressure on stones with the edge. I'll explain how I do that in a minute. BTW, I told you I tend to ramble. :) Now I am getting edges MUCH sharper, smoother and refined using only stones than I could have even imagined by using 3 strops with different grits a year ago. Like Magnesium said, anyone can do it with enough practice. Now I will strop only if I want to put a super-refined edge (according to my ability) on a knife. More than I can using just stones. So, I'm still in a boat where I use strops to improve an edge after stones. THe only change is the level of sharpness. My edges are sharper now because of all the help from people like the ones reading this, a lot of practice and finally because I'm so handsome. Well, the last reason is questionable. :) Now (until yesterday) the only strops I've been using is a horse hide on glass with CBN .5 micron spray and a bare kangaroo hide strop. These two can really put a smooth edge on an already very sharp knife. I can tell a pretty big difference when slicing news print. But for EDC knives that I use I can't tell the difference when cutting open a box, a letter, rope, string, etc. Sometimes a difference in sharpness levels is difficult to determine unless you are in a laboratory with very specific testing. Personally, if Ican't tell any difference when actually using the knife I don't consider the difference in sharpness a big deal. I still strive for it though just for fun. :)

So to remove a burr, always grind it down to the edge apex on that side, no further. Do the same thing on the other side. I'm talking about the microscopic burrs you can not feel with your fingers or even when slicing phone book paper. I just assume they are there and the last 4 strokes are as light as I can make them. One stroke per side, twice.

How I control the amount of pressure when wanting to use very light strokes. I don't think this is a secret. I let the handle lay on my fingers (one or two) and the blade rests on the stone. I'll then use leading or trailing strokes at an angle as close to the one already on the edge apex as I can manage. Even lighter pressure? Move your fingers holding the handle closer to the balance point of the knife. If the knife is balanced on one finger you can apply virtually 0 lbs of pressure. Move the fingers back just a bit and "feel" what that feels like when you stroke the stone. Then move your fingers all the way to the end of the handle and see how that "feels". You can feel how much difference there is in the amount of "weight of the blade" that is on the stone. With extremely light pressure you can easily (with practice) grind a microscopic or bigger burr down until the stone is contacting a perfectly apexed edge. Of course the GOAL is a perfectly apexed edge with absolutely now burr. Perfection may be unattainable but the closer you get the sharper your knives will be and the longer they will stay sharp.

That's enough of my opinion for about a year. :)

Jack
 
Someone linked this thread for me and wanted to say thank you for writing it. It has helped a lot.
 
Never tried sharpening a knife before. Waiting for my first "quality" knife to come in. I'm going to have to train on a cheapo for sure. I don't know if this post could have scared me any more but very helpful. On to more threads and some videos. Don't know if I should get a "tool" to assist me or just get some stones for a newbie. Still deciding.
 
RNTbone said:
Never tried sharpening a knife before. Waiting for my first "quality" knife to come in. I'm going to have to train on a cheapo for sure. I don't know if this post could have scared me any more but very helpful. On to more threads and some videos. Don't know if I should get a "tool" to assist me or just get some stones for a newbie. Still deciding.
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On my old Buck 110 , I never could get a truly sharp edge . I even managed to make it worse a few times . Then I gave it to a coworker who had it shaving arm hair in a few minutes . The point I'm trying to make is that you won't ruin your knife by practicing . Good luck and hopefully we'll both be able to sharpen our knives with a little more practice .
 
RNTbone said:
Never tried sharpening a knife before. Waiting for my first "quality" knife to come in. I'm going to have to train on a cheapo for sure. I don't know if this post could have scared me any more but very helpful. On to more threads and some videos. Don't know if I should get a "tool" to assist me or just get some stones for a newbie. Still deciding.
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Deciding to use a sharpening system or learn to free hand sharpen is a pretty huge decision for anyone just starting to sharpen. I'll give you my viewpoint. Maybe it will help. Maybe not but here goes. Dad taught me to sharpen a knife when I was about 10-12 years old using bench stones. I kept doing that for approximately a very long time. :) Many years. About 6 years ago I got into better quality knives and found my 20+ year old Arkansas stones could not sharpen the harder, better quality blade steels. This was probably due to them being CLOGGED with swarf. I didn't know how to maintain stones at that time. Anyway, I bought a DMT aligner system and learned how to use it and was getting really great results. These systems that use a clamp to hold the blade spine are good but they all seem to have quirks that while will get your edges razor sharp they can put a slightly different angle on opposite sides of the blade. Sometimes they are perfect though. Depends a lot on the knife and how much attention you pay to clamping the tool. After a year or so I got an Edge Pro apex. This system is like night and day compared to the aligner. This system is really accurate and can produce really precise results and razor sharp edges. People who get one can get their knives VERY sharp right away as long as they watch the video along with some youtube videos and they take their time getting started. If you don't try to hurry you can get good results right away but after time the results can get more refined and the edges can get sharper. It's just like any tool. The more you use it the better you get at controling it. There are several "tricks" that make a big difference after you get used to the EP. So, after about 3 years of using the EP I (for some reason) decided I just wanted to learn to free hand sharpen. Now I have been doing that for about 2 years now and am getting very good results. I have good stones and have spent A LOT of time practicing.

So now if anyone asks me which I prefer I have to say without a doubt "I don't know". :) All methods work and all have their pros and cons. But I prefer free hand sharpening I believe. This is only personal preference and is based a lot on the satisfaction of doing it myself without any help from a system that controls the angle. Of course when free hand sharpening I don't know exactly what angle I put on an edge. I can tell however if it is a low, medium or higher angle. I think that's enough. OTOH, using the EP makes it easier to repeat the same angle on knives. I used to write down the angles I used on each knife. But now I absolutely love free hand sharpening. One major key in any method is getting good tools. The DMT aligner comes with good quality diamond stones. The EP comes with good quality water stones. The EP does have the ability to use different type stones as long as they are mounted on aluminum blanks so they can fit in the EP. For bench stones there are lots of great choices. The way to save money is to decide on a stone type (diamond, water, etc.), buy them and use them. There is no need to buy different stones until after you are skilled at free hand sharpening. Getting used to the stones you are using is also a big issue in improving with free hand sharpening.

I don't know if this helped or not with a decision.

Jack
 
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