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

Posted by CliffStamp 
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 30, 2014 03:53PM
Note you can link to a post by just clicking on the post number in that forum, you can do the same here by clicking on the subject line right under an individual post.

Ref : [www.wickededgeusa.com]

Here this isn't showing that stropping is improving an edge, it just shows that using a finer abrasive increases the edge polish. The reason that it happens in stropping is that his strops are a finer abrasive than his stone.

Ref : [www.wickededgeusa.com]

Here the sharpness is degraded with stropping :

" The slight convex shaping that occurred is easy to see and the resultant loss of cutting performance was easily detected with the hanging hair test. The blade went from easily scoring HHT5 to scoring HHT4 with the occasional HHT5. "
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CliffStamp

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.

Cliff can you post a reference to Verhoeven's work on this?
Quote
CliffStamp
Note you can link to a post by just clicking on the post number in that forum, you can do the same here by clicking on the subject line right under an individual post.

Ref : [www.wickededgeusa.com]

Here this isn't showing that stropping is improving an edge, it just shows that using a finer abrasive increases the edge polish. The reason that it happens in stropping is that his strops are a finer abrasive than his stone.

Ref : [www.wickededgeusa.com]

Here the sharpness is degraded with stropping :

" The slight convex shaping that occurred is easy to see and the resultant loss of cutting performance was easily detected with the hanging hair test. The blade went from easily scoring HHT5 to scoring HHT4 with the occasional HHT5. "

Ah thanks Cliff.

Yes the theory for this is still up in the air, whereas the most common thinking in that post is that the peaks of the toothy edge peirce the tape easier and with less force. But that obviously doesn't mean that it is a" thinner" or more refined edge as seen on the pictures.

As you can see in this post [www.wickededgeusa.com] it wasn't until he used the pasted strop that he achieved HH4 and 5 levels. If the angle isn't dropped then it appears that the strop convexes the very edge and leads to a decline in performance. I think there is definitely a place for strops, it just seems to be very limited in scope at this point. Seems to be way over rated in today's day and age. I think that this bears more research :-D
cKc
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 30, 2014 10:04PM
Travis, when I strop its about 3-5pps and I always notice an improvement in the edge quality just from that little amount over coming just off the stone.. its probably just cleaning up the edge a bit.. but I can also see the impact under microscrope from that little amount..

the issue will come from doing what VV and others do, in using a strop as a sharpening device rather than a clean up device.

----------------------------------------------------------------------
It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 01:57AM
Verhoeven : [www-archive.mse.iastate.edu]

A few points :

-a theory is a position in science which is well supported by evidence to the point it is acknowledged as a fact


The problems with discussions about stropping and other issues is often that arguments are being made which are not looking at what is changing and this is critical in any analysis.

If you sharpen a knife on a stone and then take it to a strop which has a finer compound then the edge will get more polished and the push cutting sharpness will decrease, the slicing sharpness usually doesn't and can decrease very rapidly.

This has nothing to do with stropping vs stone, it is just the effect of the higher polish.

Here is the relevant question :

-if you form an edge on a 1000 grit stone and then take it to a 1000 grit strop what will happen

There is only one thing which can happen, the edge can degrade because of rounding and contamination/dirt on the strop. If the edge actually improves it just means that it wasn't sharpened properly on the stone as if it was then what could possibly improve it?

Here is a question, if I take your favorite stone and :

-get it dirty
-put enough wear to make the surface very uneven
-mix other abrasives onto the surface

Would anyone think that would be better for sharpening?

If you look at people who strop you will find, and this is the part which is amusing, people who really refine their edges to high standards will :

-use very hard mediums/backing on the strop (to prevent edge rounding)
-protect the surface from contamination (as otherwise the dirt has more of an effect than the stropping compound)
-do very minimal passes (prevent edge rounding)
-use very light force (prevent edge rounding)

Now just think about that and it should be obvious if you take that one step further you have a benchstone and you don't have any concerns about edge rounding.

The main benefits of stropping are :

-on very soft backing the slop from the deformation will catch any edge angle if you press hard

-very fine compounds are very inexpensive compared to very fine stones

How much is a 30k Shapton vs 0.5 micron buffing compound?

Again, the big problem with stropping vs stone comparisons is lack of equal grits, yes a fine grit produces a higher polish than a coarse grit - who debates that? However does a 5 micron loaded piece of leather actually produce a sharper edge than a 5 micron quality benchstone?
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 03:06AM
One thing I noticed about stropping advocates is how many different attempts to explain the mechanics behind the process there are. Some of them took very techincal things like fluid dynamics(and other sciency buzz words) into consideration for their explainations. But all the explanations seem to contradict one another.

me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 03:21AM
So far all I'm sure of now is I want a 30K Shapton Glass Stone. On the down side it's very expensive for a stone, but on the up side, it would last generations as long as no one gave it to their teenagers. I'm convinced, and trying to convince my daughter, that boys between 11 and 30 are just shaved apes that speak English (here). I'm sure that age range would break a 30K stone just for squirts and giggles.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 06:11AM
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me2
So far all I'm sure of now is I want a 30K Shapton Glass Stone. On the down side it's very expensive for a stone, but on the up side, it would last generations as long as no one gave it to their teenagers. I'm convinced, and trying to convince my daughter, that boys between 11 and 30 are just shaved apes that speak English (here). I'm sure that age range would break a 30K stone just for squirts and giggles.

Nonsense there are plenty of older men without any sensibilty.

Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 12:51PM
Here is a stropping comparison which takes a edge off of a 0.5 micron stone and then strops it on leather, wood, and various compounds. In all cases the edge just degrades.

Note the 0.5 micron stone is actually made using glass and sandpaper : Ref : [www3.telus.net] .

The important part here isn't the actual experiment, which is interesting but the reasoning given and the way in which the work is done.

Now there are compounds finer than 0.5 microns, but you can get finer papers in sheet form as well and you can also make the strop on sheet glass with a neutral abrasive - which again is just making a stone.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 01:08PM
Thats the trouble with generalizations. I'm cettain there are exeptions in that 11-30 range. She just needs to understand that they sre exceptions, not the norm.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 01:15PM
Here is another take on the edge rounding issue : [www.otec.de]

This is a critical topic in the tooling industry : [www.sciencedirect.com]

This is not well addressed in hand knives, but it is the actual question which underlies vague arguments such as :

-can a knife be too sharp

Chum actually asked about this as well recently when he noted could you not sharpen to a full apex on HC steels to make them more stable. This is exactly what the above is doing, they round the apex to provide maximum stability at the required cutting ability.

Note the cutting is all push based.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 02:27PM
Cliff, could you summarize the second link, I don't want to spend 40 bucks to read it. (Science direct).

I may have misunderstood what chum was saying earlier. I thought he was talking about optimizing the edge angle based on the steel to provide the stability. But the way you put it he was suggesting leaving the apex the width of what is stable. So a 10dps microbevel with an apex 10microns wide for steel x but steel y would have a 10dps micro bevel that is 22microns wide? Is this what he was saying?
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 03:48PM
Mark,

The basic idea is this, if the edge is left rounded at a high thickness it has a higher stability, however it has a lower cutting ability which increases the loads on it. You have to thus find the "sweet spot" which has the edge just thick enough so that it is stable and no thicker. This ensures that the minimal forces are applied to it in use.

Yes, a fully sharp edge on steel would be about 0.1 microns wide at the apex. However it is likely that a thicker apex would have a better lifetime due to not having the initial rapid break down. My concern with this is that outside of very special machinery (see the above in the tooling industry) how could you in hand sharpening know when to stop so your apex was exact 1 micron wide for example?

I would think a more suitable approach would be use of micro-bevels because just consider that a 90 degree micro-bevel is essentially a full flat anyway. The optimal edge would be one then which had a micro-bevel which was just wide enough to stabilize it.

Note in all cases it reduces down to the same constraint :

-the thickness has to be just enough to keep the material from breaking, any more/less and it isn't optimal
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 03:54PM
Here is another comparison which is interesting : [sharpeningtechniques.blogspot.ca]

Note the main problem here is that the very coarse initial edge leaves the apex so rough that the edge never gets refined and even on very fine stones and strops the edge picks up coarse irregular finishes due to the harsh scratch patterns intersecting the edge.

This is one of the main problems with burr sharpening, especially with x-coarse stones if you are trying to achieve a very fine polish and especially if you use a non-slurry based stone system.

I talked about this in a recent video where I noted that the condition of the bevel *before* you apply the micro-bevel will have a dramatic effect on the sharpness and lifetime and that burr minimization and removal are critical, the former being more important than the latter.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 04:41PM
This correlates to some sharpening I have been doing lately. I have been working to get a freehand mirror polish using sandpaper followed by stropping with diamond paste to do the final polish. Between the last grit paper 2500 and the strop I have been destressing the edge (thanks rstravis) then I apply a 1200 true micro bevel as the cutting edge/apex. The thing I have noticed but never tested is the edge is quite sharp after one 90deg destressing pass. That would be the plateau Chum was talking about. Next time I sharpen some knives like this I will leave one with out the micro bevel to see how it performs., or if it has any functional knife benefit.
some interesting "claims"...rharden the steel etc







Edited 1 time(s). Last edit at 01/31/2014 07:05PM by Francesco.
some interesting "claims"



Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 07:21PM
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Mark a
I may have misunderstood what chum was saying earlier. I thought he was talking about optimizing the edge angle based on the steel to provide the stability. But the way you put it he was suggesting leaving the apex the width of what is stable. So a 10dps microbevel with an apex 10microns wide for steel x but steel y would have a 10dps micro bevel that is 22microns wide? Is this what he was saying?

Cliff used to post graphs showing how an edge would decrease in sharpness as he continued to cut cardboard. Eventually you would see a plateau on the graph where the edge just wouldn't decrease in sharpness any longer because it was sufficiently blunted to the point where cutting cardboard no longer deformed the steel. This is why I called them "plateau" edges.

I was just suggesting if it made any sense to set the edge like this initially, and if there were a way to optimize the edge where it would be at a plateau with the thinnest edge possible.

I looked for examples of Cliff's graphs but I couldn't remember where he was posting those, and came up empty.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 10:08PM
Thats an intersting question and a point of contention by some with Cliff's work. I dont think you can intentionally sharpen a knife to be at that plateau from the beginning. It would be like sharpening and then giving the edge a destressing pass with ~5 grams of load into your finest stone.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 10:47PM
Quote
me2
Thats an intersting question and a point of contention by some with Cliff's work. I dont think you can intentionally sharpen a knife to be at that plateau from the beginning. It would be like sharpening and then giving the edge a destressing pass with ~5 grams of load into your finest stone.

It's interesting that you mentioned destressing the edge. You do this to get rid of the weakened and damaged metal. Setting a plateau edge would be like cutting out the middle man. There would be no need to destress the edge as you would have aleady done it spinning smiley sticking its tongue out

I had originally thought that a very high wear resistant steel would be ideal for this type of edge, but since the goal would be to set a plateau edge at the highest sharpness possible, it might make more sense to use a steel with a high edge stability. lol... aeb-l.


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 10:51PM
Some of my early (unsuccessful) edge retention testing was causing me huge problems as the blade was never dulling. Seems like this may have been a factor, the blades were already at the plateau when I started so regardless how much I cut I could not measure any decrease in sharpness.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 10:58PM
Quote
Mark a
Some of my early (unsuccessful) edge retention testing was causing me huge problems as the blade was never dulling. Seems like this may have been a factor, the blades were already at the plateau when I started so regardless how much I cut I could not measure any decrease in sharpness.

If they could cut the medium you wanted them to cut, this would be a positive, correct?


Chumgeyser on Youtube
E-nep throwing Brotherhood. Charter Member
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 31, 2014 11:17PM
Yeah. It would. I can't find the paper I used to record the measurements but I think I cut somewhere around 250 feet and all that happened was it stopped push cutting newspaper. It was still slicing copy paper better than most you tubers sharpness demonstrations.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
February 01, 2014 01:52AM
When I first started testing knives, in the mid 90's, I began to wonder what all the fuss was about. Even my least expensive ones would cut for a while, especially on wood and paper. Now, the same is true, I just have higher standards. You guys are just sharpening a knife properly. You haven't reached the plateau yet. I've cut 30 to 40 feet of cardboard and still had my best home made knife shave above my skin on my arm. (M2 at 65 HRc - love that stuff) When I started recording the load to push cut thread on a scale, most knives, even my cheapest, will stabilize around 120 to 160 grams. This is after cutting 1200 slices in cardboard strips 2 inches wide (roughly 2000 inches of cardboard. Edges at this point will still shave hair off my fingers, just barely, but will slice even phone book paper. It takes a lot of cutting to dull a knife to the point it won't cut typing paper, if it was properly sharpened and the damaged steel removed from the edge.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
March 30, 2014 03:40PM
I wanted to post on this thread to give everyone a work of caution. I was using Cliff's 3 step method to sharpen a paring knife, going very fast to rebevel the edge. During this, the blade slipped off the stone and into my finger. The cut is going to take about a month to fully heal. If you use the scrubbing action in the video, be VERY CAREFUL. My main mistake was switching from an 8" stone to a 6" and going too fast. I will likely be adding a Kevlar glove to the Norton Economy stone to prevent further accidents.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
March 30, 2014 06:37PM
The way I sharpen by holding onto the stone is extremely dangerous. I do it because I am watching programs when I am sharpening. I would not recommend it in general for the exact reason you noted.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
March 30, 2014 07:25PM
lol to paraphrase what cliff said;

what i do is really dangerous but, i do it while not paying attention!

operator level 9000
I find something like this to be very helpful: [www.sharpeningsupplies.com]

Haven't lost any digits going fairly quickly on the larger grits.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
March 31, 2014 02:40AM
One of those would be nice, but I don't particularly like water stones, and was using the stone in one hand and the knife in the other. I am able to go faster and keep better angle control that way, until cutting myself. Now that you mention it, one of those might be nice.
KWB
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
April 01, 2014 09:16AM
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me2
When I first started testing knives, in the mid 90's, I began to wonder what all the fuss was about. Even my least expensive ones would cut for a while, especially on wood and paper. Now, the same is true, I just have higher standards. You guys are just sharpening a knife properly. You haven't reached the plateau yet. I've cut 30 to 40 feet of cardboard and still had my best home made knife shave above my skin on my arm. (M2 at 65 HRc - love that stuff) When I started recording the load to push cut thread on a scale, most knives, even my cheapest, will stabilize around 120 to 160 grams. This is after cutting 1200 slices in cardboard strips 2 inches wide (roughly 2000 inches of cardboard. Edges at this point will still shave hair off my fingers, just barely, but will slice even phone book paper. It takes a lot of cutting to dull a knife to the point it won't cut typing paper, if it was properly sharpened and the damaged steel removed from the edge.
. But this also maybe dependent in what type of cardboard it is, box weight and how clean the cardboard is I took a knife I made made 20 or 30 cuts at work and the edge was still there but very roughed up, reason being it was an extreme weight box don't remember the rating but it was the thickest stuff I have ever seen. In top of that in was cover in the equivalent of 200 grit sandpaper. In disbelief I tried my pretium and same thing happened. I find double insulated extension cords make a good cut test as they are usually constant. High pressure rated hydraulic hose as well but your hands will tire rather quickly. The only thing that I seen that has posed a problem cutting is conduit wire like the kind in your house and back/skid steer tires.
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