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

Nice job on your write-up. Right on with the loop. The first time I looked at a blade with a loop. It was amazing what you saw. Could not believe how much of the blade had not yet been touched.
 
me2 said:
I suppose I'll be the voice of dissent on a couple of points. I have not found drawing through a board to be aneffective way to remove a burr, even the large foil like ones left after my belt sander. I have also not found stropping on a stone or hand stropping on leather w/ or w/o compound to be effective. The only method I've been able to use that reliably removes a burr is to use elevated angle passes on the stone, sometimes quit elevated, 35° or more. Finally, use of finer abrasives willproduce a sharper edge in terms of lowering the microscopic width of the edge. The edge width has been measured to be reduced from 1-3 microns to less than 0.5 microns by going feom 1k to 6k stones.
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I remove a wire edge by dragging the edge through the backside corner edge of my (wooden) strop. It works very well. Oh, and the strop itself also works quite well.
 
Strigamort said:
I remove a wire edge by dragging the edge through the backside corner edge of my (wooden) strop. It works very well. Oh, and the strop itself also works quite well.
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How big is the burr? Can you see it? If not, how do you check for it? The burrs I get just wont come off without some other way besides hand stropping or drawing through a board. I cant see them, but can feel them when I draw the blade backwards over my arm or head.
 
Thank you. This is a great post. I've used and sharpened knives for years, and I've been hanging around this forum for a long time too. Up until comparatively recent times I've simply swiped my blades over a stone then maybe used a steel, and of course they have performed well enough. This thread has helped me to understand the finer points and terminology of sharpening science that so many folks talk about here. Best wishes from New Zealand
 
Very good thread!

Wish I found this before I started sharpening...

I suggest a decent but cheap knife to practice on instead of ruining a $350 Chef knife haha!

I bought a $25 caddie slicer to practice and 10 years later it still serves me (retired to home kitchen as long pairing).
 
This one of the most pragmatic and well related lessons I've read. You literally explained everything I've been questioning through a small spiel.
As a fledgling in the arduous realm of sharpening, you've just saved all of my knives and much of my time.
Thank you sir.
 
I've been really trying to improve my freehand technique and abilities recently and this thread was very helpful and informative. I've read many threads that are great about giving practical advice on technique, stroke, angles,etc. however, knowing WHY something should be done in a particular way has really improved my sharpening.

Thanks.
 
Ok so I just registered after trolling around here for weeks. Anyway not sure if this is a good place for this but I'm just so damn excited that I finally sharpened a knife freehand! It was just a case ss but the fact I brought it to slicing phone book paper all the way down or across with hardly any sound at all has me all giddy that it was freehand (spyderco stones just held in my hand) so I truly have a grasp on burrs and angles and the sound the stone makes so I will go now and dull up something else to freehand! It's a cool feeling noone else would really understand. Freehand dudes!
 
Fistyrbuns said:
Ok so I just registered after trolling around here for weeks. Anyway not sure if this is a good place for this but I'm just so damn excited that I finally sharpened a knife freehand! It was just a case ss but the fact I brought it to slicing phone book paper all the way down or across with hardly any sound at all has me all giddy that it was freehand (spyderco stones just held in my hand) so I truly have a grasp on burrs and angles and the sound the stone makes so I will go now and dull up something else to freehand! It's a cool feeling noone else would really understand. Freehand dudes!
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Welcome to the forum! :D I'm glad you found this helpful, and I'm honored your first post is in my thread.
 
A most excellent dissertation, sir. I'm relatively new to this forum and, since I've been freehand sharpening knives for 45 years or so, I took my sweet time deciding to read others' opinions on the subject. I truly wish I had had your post in hand when I started. I hate to remember how long it took me to discover(the hard way) what you so eloquently explained in a few minutes' reading.
I have taught my children the same techniques you described (minus the loupe-damn! I wish I'd thought of that! Been clunking around with a huge magnifying glass...). With your permission, I'll print a copy for each of them of your original post to go with the sharpening systems I just ordered for them. I can't think of a better tutorial. Unless you're gonna use one o'them motorized, slotted, chef-knife thingies, you need to read and practice exactly what's in the OP. Thank you.
 
One of the most informative posts I ve seen in my time at the forums. Puts things in a nice perspective. Thanks for your effort in crafting that discussion.
 
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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Thanks! Very helpful. :thumbup:
 
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.
 
Thanks for the excellent post. I have been sharpening for many years with hit or miss results. I recently purchased a fine and xfine DMT bench stone and a leather strop. After reading your post and learning that a sharpie can help you keep a more consistent angle I finally got things right and now have a few traditional folders and a leatherman with hair shaving edges!!!
 
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