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Basic three step knife sharpening : destress the edge + shaping + finishing the apex

Posted by CliffStamp 
Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 09, 2012 06:53PM
Video :



me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 09, 2012 07:54PM
Good stuff. How important do you think it is to destress a knife like the one you demonstrated with? For heavy choppers, I've read where you found it very benficial, but I just wonder how much stressed steel is there for a kitchen knife or light duty paring knife. Of coarse, used properly and only for peeling/paring fruits and vegetables, a paring knife might not need sharpening for over a year.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 09, 2012 08:11PM
It would be possible for the edge to wear completely smooth but I would doubt that it happens often. An easy way to see how much of the edge is deformed is just to give it a light pass on a smooth steel, if the edge responds strongly then it was heavily deformed and is not aligned. The part I always found curious was people paying a lot of money for high end steels and then sharpening them in such a way that they have the strength and durability of the most basic cutlery steel with the worst HT you could imagine.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 09, 2012 08:58PM
I'm still conviced that most of what people see in terms of edge holding differences are the result of sharpening differences. I've got my 204 technique down. However, I've been using it for so long, I'm lacking in benchstone technique. I learned this trying to sharpen that A2 kitchen knife I made. This also shows how, once you get a good edge on a knife, profiled the way you want and actually sharp to start with, it's easy and quick to maintain it. I've resharpened my Cold Steel Scalper at least 4 times just by using the procedure in my video with only the 204, each time taking less than 2 minutes. The same goes for my Delica. Even with the very thick edge, the microbevel just takes a minute or 2 to sharpen. The cherry handled kitchen utility, which my wife likes a lot, has been resharpened 3 times in less than 2 minutes each on the 204. I'll have to try this with a cheap $5 stone and see what happens.

I also agree about the high end steels. One really needs to have good information and the experience to go with it to get more than the most basic performance increase from higher end knives/steels. I've seen people perfectly impressed with their Busse knives, only to find huge burrs on the edge when I get to actually handle one.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 09, 2012 09:22PM
I would agree and the evidence is rather strong :

1) Do a quick check on YT video's where people are heavily stropping blades to the point it is almost a religious experience. This edge is so stressed that the edge aggression is non-existent and the edge retention is a fraction of normal.

2) Note how many comments are from people having to put edges of 20+ degrees on blades to stop chipping on cardboard (?!). I am cutting up plywood with 4-6 dps blades and yet people are seeing edges at 15-20 dps chip on recycled paper?

3) In general, how many comments that steels such as AUS-8 etc. will go dull instantly after just a little work. I have done cycles of 200+ slices into 1/8" ridged cardboard with knives made out of 420J2 and they still easily slice newsprint (they could push cut before the work started). How many people make that many cuts in a day?

4) The large amount of people impressed with a blade that slices printer paper. Note in the video even after the shaping stage the knife will easily slice newsprint and it isn't even start to be actually sharpened yet, that is still just shaping.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 10, 2012 01:02PM
So what do you do when you move to a finer stone?
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 10, 2012 02:29PM
If I wanted to raise the bevel polish I would just add the other stone finish and would not be as particular about the intermediate finish as it is just to reduce the work of the final stone. If the steel has a very high grindability I may work on the entire apex bevel, if the grindability is low I would just work on the micro-bevel.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 10, 2012 03:01PM
So basically, once the edge is apexed, you just keep going with the polish and alternate passes until its where yoy want? Theres no need to shape or apex again though a deburring step just in case probably wouldnt hurt.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 10, 2012 05:00PM
Yes, the shaping is only done with the coarse stone so there is very minimal work required past that on finer stones. Of course if you want a fully matched bevel finish you have to work the entire apex bevel with each stone which is fairly time consuming hence I don't do it. But then again I cut cardboard, sheet rock, shingles, etc. with the knives so polished edges are not overly functional as they are only polished until the first cut.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 12, 2012 07:55PM
Just gave this a try. 220 grit King HOH stone and the RADA Cutlery Santoku. The edge has been reground and was basically trashed from heavy handed grinding, so I raised a burr along the entire length, then cut into the stone to remove it. Then did it again. After that, the edge was honed until it stopped reflecting light. I'm pretty sure there was a burr there, but I couldn't detect it with my fingers or by stropping on the back of my head. I gave the edge 2 deburring passes per side at an elevated angle, the started alternating strokes on the 220 HOH stone. After about 30-40 passes total, the edge would cleanly slice writing paper (the 3 lined paper used to teach kids to write). After cleaning the stone and giving the edge a few more passes it would whittle beard hair. I refined the edge on the 1000 grit side and it would catch hair above my head and tree top arm hair. This took about 10 minutes, or 3 songs on the local country station.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 12, 2012 08:25PM
It usually takes me another 1-2 minutes to get the edge to push cut newsprint, and the initial shaping can take another minute if the edge is really heavily damaged or I am changing the angle. Can you get the same sharpness off the 220 directly?
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
November 12, 2012 08:41PM
I don't know. I plan to apply this to my sharpening angle blocks and add that degree of control over the edge. I probably could then. The 1000 grit edge would whittle head hair in a few places. I've never been able to do that off the 220 side. This edge will probably get better after a few sharpenings. It had a rough life during the regrind. On another note, the new 5 dps back bevels are only 0.25" wide or less, and the whole knife has an 80 grit finish now.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 05, 2012 08:17AM
I don't think I've watched another YT sharpening video that suggests you clean off the edge in the same manner you do Cliff, or that you even clean the edge off at all. I don't even think Spyderco mentions this in their Sharpmaker video (not positive since it's been awhile since I watched it.)

What you are suggesting makes sense, but it is hard to imagine that all of the little micro chipping and micro dents actually get taken care of by such light pressure and so few strokes. I'll be adding this step to my sharpening for sure.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 05, 2012 12:41PM
The edge of a knife is very fine, it will not take very much force at all against a sharpening abrasive to grind off a lot of material. Even a feather light touch will flatten the edge completely and leave it very dull. If course if the edge has visible damage then more than one light pass might be necessary.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 05, 2012 02:54PM
Quote
Chum
I don't think I've watched another YT sharpening video that suggests you clean off the edge in the same manner you do Cliff, or that you even clean the edge off at all.

The vast majority of people who talk about sharpening have no idea what is happening physically on the edge of the knife. If you think about what is actually happening then the idea of sharpening an edge while there is still weakened metal on the edge is simply idiotic, you are shaping damaged, worn and stressed metal. The most extreme nonsensical example of this is the insanely popular argument to strop instead of sharpen on stones to "extend" the life of the edge. If you are going to do this then it is pointless to buy anything other than a 420J2 knife because sharpening edges in that way will take the best quality HT'ed tool steel and reduce it to brittle, soft and weak steel at the edge as you are just constantly fatiguing the steel.

Years ago I experimented with stropping and quickly saw it destroy knife edges. The worst case was stropping a Battle Mistress to keep it sharp while chopping and eventually seeing the edge chip and roll on woods. This was just the effect of the edge constantly getting micro-damaged and this steel instead of being removed was just pushed back into place. This is why people love stropping the edge "appears" to get sharp very quickly because a lot of blunting is deformation not wear hence they are just pushing weak steel back into place. I also did a series of experiments where I sharpened a knife, did some cutting and then stropped and repeated, the edge retention kept getting less each time and quickly degrades high quality steels to flea market knives.

This is all basic physics and metallurgy.

The real curious thing is when you get people talking about forging and how they are doing all this work to produce the finest quality steel, working down large billets to knife shaped, week long HT's and then sharpening by stropping. It is so absurd that it is comical. What did you do all of that work for to then take the most important part of the knife, the edge, and then destroy it by fatigue and galling and worse still, maintain it even worse. But it is no sillier than making knives out of the highest cost steels available and extremely expensive heat treatments and then over heat them at the edge, draw the temper and the micro-crack them by quenching in water on steels never designed for such rapid quenching.

The most absurd part is that this is a known problem solved in the literature and given the ease of information dispersion due to the internet this is just abdominal practice. A generation ago if a dude was just making knives, unless he had an academic background this information was not trivial to get, but now - it is a pretty silly way to make knives (or do anything else). That companies making extremely expensive knives are still burning edges is really laughable and the worst part is (a) they know about it and (b) people tolerate it and almost expect it.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 05:26AM
Regarding stropping
I quite agree that stropping isn't that great, at least used as some do-it-all solution.

One question that is risen is regarding edge being pushed back into place. Guess most "knife enthusiasts" would agree (at least if they understood what's happening) that it is not a bad thing.
Yet there are knife steels which main purpose, I guess, is pushing back edge in place, and those seem used quite extensively in food industry.
I also remember stropping machine that used quite aggressive rubber stropping wheels.
Or the obvious barber strop.
Arguably all those people strop their blades frequently. And they cut mostly soft materials.

Since these contexts are professional, if not industrial, you'd expect some studies having been done on subject so these are probably economically sound practices (on the other hand the Japanese doesn't seem to bother much with stropping).

Now question would be is it mostly because of the kind of work, or do ductile steels lend themselves better to that type of use? Is there some work hardening here (yeah, I know, buzzword, but people have been, as cheap expedients, cold hammering scythes and other tools for quite a while, so it is quite mundane really).
One could also consider strops, particularly loaded strops, simply/mostly as fine abrasives hones.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 11:30AM
Good points bubo. It's not that I don't believe Cliff on his anti-strop position, and his explanation does make sense, however I'm not convinced that stropping ALWAYS leads to a weakened edge.

Cliff... can you give us your best high school science teacher explanation of why stropping weakens the edge, please? I want to try to convince my Dad and some of my friends that stropping isn't the way to go, and I'm sure you can explain it better than I. They won't be convinced easily.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 11:55AM
Chum I would take a paper clip and show how after you bend it back and forth a bunch it breaks. Then explain that is what stropping does to a knife edge. I also figure that stropping a freshly sharpened edge that isn't damaged wouldn't be as weakening, besides how else are you going to be able to use 0.01um diamond particles to sharpen?

On the barber strop point, I notice that in the straight razor community everyone is all up on end about how delicate their edges are. I have come to believe this is produce from months to years of stropping before finally being sharpened on a stone.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 12:22PM
Quote
Old Spice
Chum I would take a paper clip and show how after you bend it back and forth a bunch it breaks. Then explain that is what stropping does to a knife edge. I also figure that stropping a freshly sharpened edge that isn't damaged wouldn't be as weakening, besides how else are you going to be able to use 0.01um diamond particles to sharpen?

On the barber strop point, I notice that in the straight razor community everyone is all up on end about how delicate their edges are. I have come to believe this is produce from months to years of stropping before finally being sharpened on a stone.

Good idea on the paper clip demo/explanation.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 02:37PM
Quote
bubo
Now question would be is it mostly because of the kind of work, or do ductile steels lend themselves better to that type of use? Is there some work hardening here (yeah, I know, buzzword, but people have been, as cheap expedients, cold hammering scythes and other tools for quite a while, so it is quite mundane really).
One could also consider strops, particularly loaded strops, simply/mostly as fine abrasives hones.

Steels with a high fatigue point would work better, but generally you would not want those as knives as they are quite soft and designed for something very different than retaining a sharp edge. The work hardening is in the wrong direction, it will weaken the edge. Similar to folding a piece of paper will only make it stiffer in the opposite direction.

Yes, strops are fine stones, but consider the quality and loading of the abrasive and how would you rate a stone which was similar. It would be rated as a horrible stone, cuts slow, loads fast, abrasive is inconsistent (in general most people don't use quality stropping compounds they use compounds not intended for such use), and fresh abrasive is never released.

Quote
Old Spice
I notice that in the straight razor community everyone is all up on end about how delicate their edges are. I have come to believe this is produce from months to years of stropping before finally being sharpened on a stone.

One of the more nonsensical things about many of those guys is the fact that if you discuss sharpening razors as if they were knives then it is similar to going on BR's forum and asking about burnt edges. A razor is simple a knife of a very particular geometry and the edge angles/thickness are not extreme compared to knives I own and use. As you said, the edges are extremely delicate because they are over stressed in sharpening.

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Chum
I'm not convinced that stropping ALWAYS leads to a weakened edge.

That is the things about physics, it doesn't care if you believe it or not.

That being said, you should never accept something simply because I said it, that way leads to the dark side. You should only accept something because it makes sense.

I don't even accept something just because I think it is true, that is why I spend so much time counter sourcing data. The minute you accept that you are the authority and don't need external confirmation is the minute you stop looking for the truth and instead start creating one.

Beach has a nice page on and discussion of stropping : [www3.telus.net] . His summary is one of the best I have seen, if stropping improves your edge then it was not properly sharpened in the first place.

Consider :





Now how would you rate the "stone" he makes compared to any of the cheapest stones you can buy? Well the same holds for strops in general. Now you can make a decent strop using an actual honing abrasive, but even then you still have an exceptionally poor stone which has inconsistent grade coverage, loads fast, does not release abrasive etc. . What is the reason for doing that?

The curious part is that some people will take a very strong position on anti-steeling but still promote strops :





That is like arguing that drinking pepsi is anti-health but coke is a great way to get healthy. How is one good and the other horrible?
RFL
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 03:06PM
When I flatten out an apex bevel (increase bevel height, reduce grind angle) I naturally use the coarsest stone I have. Furthermore, I am only attempting to grind off the shoulder if the blade is very cheap/soft. Since these are the best ingredients (coarse abrasive, cheap steel) for unintentional burr formation, burr elimination is problematic. Usually, I just grind off the burr the best that I can but I am aware that a micro burr always remains. This micro burr is always dealt with by stropping; however, if the edge is noticeably different after a few strokes, then stropping may not have been the best choice. But it is damn quick.

I assume that micro burrs cause a sharp edge to tear phone book paper. I usually test sharpness on phone book paper, but sometimes I use newspaper. An edge that slices newspaper cleanly, will sometimes catch and tear phone book paper. The newspaper must be stiffer due to clay additives, this is why some strop on it. Most often, the tear is on the very edge of the paper and after 1/4" turns into a clean slice. Next time this happens I will not resort to stropping; instead, I will use an UF ceramic with deburring strokes.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 03:39PM
Quote
CliffStamp
That is the things about physics, it doesn't care if you believe it or not.
lol true... but theory isn't the same as fact, and scientist often have such a firm belief in their theory that they begin to refer to it as immutable fact. Are you telling me, Cliff, that it is indeed a fact that stropping ALWAYS will lead to a weakened edge?

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CliffStamp
That being said, you should never accept something simply because I said it,
I don't, although in the realm of cutlery I'm more inclinded to believe you than not.

Quote
CliffStamp
that way leads to the dark side.
I'm all Jedi, all the time.

Here's the problem I have with the anti-stropping stance. If the pressure you use is light enough you shouldn't be folding, or bending the apex. It should work the same way as if you were sharpening on a stone, no? The difference is you are putting pressure on the pull stroke instead of the push stroke. Does that make any sense?

I pretty much buy into your anti-stropping theory (yes that's what I'm calling it right now.) I just have this hiccup concerning the pessure being put behind stropping.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 04:55PM
Quote
Chum
[but theory isn't the same as fact, and scientist often have such a firm belief in their theory that they begin to refer to it as immutable fact. Are you telling me, Cliff, that it is indeed a fact that stropping ALWAYS will lead to a weakened edge?


A theory and a fact are very different, a fact is just a data point, i.e., if you drop an apple you observe it fall, it is fact that the apple fell. A theory is an attempt to explain an observation, which starts out as a hypothesis (just an idea) and after many, many tests and no direct contradictions becomes a theory (i.e. gravity is one of the fundamental forces and its nature is the theory of gravity). It is very rare that a theory would ever be completely refuted, but they are constantly refined as for example Newton's approach to gravity is still perfectly valid for all of his observations (it has to) but it doesn't hold at extremely small scales (quantum theory has to be used) and as well it doesn't hold at extremely high speed (general relativity has to be used).

Now as for stropping, you can strop and do nothing, just strop on a non-abrasive media very light - nothing happens at all. If the media is abrasive then it has to produce an inferior edge than edge-into honing for one reason, the scratches will tend to leave/deposit material at the edge which will not happen on edge-into honing, you can see this directly in Verhoeven's work where he compares the two directly and shows that edge trailing produces larger burrs. This is with ideal technique. With non-ideal technique you will start to see edge fatigue issues, galling/adhesive wear, and similar other effects. It is nothing more than trying to sharpen with a dirty and loaded stone, why would you ever do that and argue it is optimal to before you start to sharpen a nice knife, take a cheap one and grind it into the stone to load it up with metal and debris. The logic there should stand out as obviously flawed, but that is the nature of stropping in general, scrub a mix of chalk, and a hodge podge of abrasives into leather and wipe the knife on it and continue doing it even when the strop is heavily loaded.

Quote

It should work the same way as if you were sharpening on a stone, no? The difference is you are putting pressure on the pull stroke instead of the push stroke. Does that make any sense?

The direction has an influence yes, but so does the nature of the abrasive, just think about the abrasives in a strop vs a quality stone and imagine what a stone would look like if it was similar to a strop. It would be like taking a nice water stone, putting it in a bucket of grease, rolling it in dirt, drawing on it with chalk and markers and then dripping wax on it. Now if I put two stones in front of you, one like that and the other a nice cleanly lapped and fresh cross hatched surface - which would you rather use and which would you say is clearly less effective?


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RFL
Most often, the tear is on the very edge of the paper and after 1/4" turns into a clean slice.

Once you get into it the sharpness required to continue the cut is less, at the start there is very little resistance to the paper just bending rather than being cut, that is while only really the start matters, but the long cuts are just dramatic for YT presentations, unless you have an uneven edge at which point it can snag.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 06:06PM
Verhoevenalso showed that the finest edges in the study came from stropping on diamond on leather, and that the larger burrs produced from "stropping" on the 6k stone were not evident after stropping on CrO loaded leather. Not to say that stropping removed a burr that formed from the edge trailing strokes on the 6k stone but that one did not form when stropping following edge in passes on the 6k stone.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 06:30PM
The burr formation would scale, be percentages, at very fine finishes where the edge burr is 0.3 to 0.5 microns, even very large differences, say 25% or more would be barely visible due to the size of the random deviations, i.e., the signal is hidden in the noise.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 06:48PM
I know. I'm just poking at you. What do you think about honing films? The supplier said to only strop, but I had really good results from edge in passes on 0.3 um films on glass. I switched back to edge trailing after cutting a couple of films though. If you have a gentle touch, they work well though. I think they're similar to what Brent Beach uses.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 06, 2012 09:00PM
I tried many of the films years back, they are better than making a strop in terms of consistency however I never saw the point. You are basically buying a stone which is what, a hundredth of a mm thick and once it is loaded/worn you just throw it out? Why not simply buy a stone and use it a lifetime and then as you are dying give it to someone else. By the time we have invented nano wires to cut with the stone may be used out. I have a hard black arkansas my grandfather used which I know is at least 40+ years old, it looks pretty much new except for all the pieces out of the sides where it was used as a doorstop for 10 years after he died until I saw it and recognized it under the layers of dirt/grime.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 12, 2012 07:53PM
Well, long term it makes sense to buy the stone, but short term, the films are only about $2 each and a pack of three last me nearly a year.

Just a little more on this method. I sharpened my RADA paring knife using this procedure. It will now split a beard hair off just the 220 side of my 220/1000 water stone. Took less than 5 minutes. I tried ot on my delica as well but I think I did it wrong. It appears to be important to backhone after deburring on the coarse stone before moving to the finer stones. I deburred at 30-40 dps, then went straight to the 1000 grit side. The edge was much less than what I know the 1000 side will produce.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 15, 2012 12:34PM
Ugh... I've been practicing like crazy and I just can't get my knives as sharp as Cliff does. I think I'm just not able to keep my angles consistent. Has anyone tried those angle guides that you clip on the spine of the knife when sharpening?
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 15, 2012 12:48PM
I'm not sure what you mean by consistent, but watch the video using the 24 grit stone. The knife and stone are both moving all over. I don't really thing exact angle control is that important. If it were, we'd all have to use jigged sharpeners. I think "just getting close" will work fine, but the edge will look pretty rough.
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