The end all discussion - Polished edge retention and use vs "working edge".

230grains

230grains

Joined
Jul 10, 2009
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I crazy polish all of my edges, on convex knives I zero edge them removing the shoulder and blending the edge into the grind then polish up to .25 micron on certain knives. I just sold one of my knives and the buyer seemed to like the edge as he posted a youtube video of it seen here :

http://www.youtube.com/watch?v=ZTF9YQ5wG5g

That edge will push cut fine newspaper, not draw cut, but push straight up and down, I know because I tested it right before I shipped it after its final sharpening. That knife has been used to chop down more than a few trees and process quite a bit of firewood, that same knife with a super high polished convex edge. It holds up just fine, but some would say because its high polished, its not going to last. Lets once and for all lay the cards on the table. Voice your support for high levels of edge refinement vs a "toothy" working edge for retention. I'm not asking your preference of which you think cuts better, but which you feel holds an edge better.
 
8k-10k is around the point of diminishing returns for edge holding on a good steel with a proper heat tratment. Polishing to finer levels increases cutting ability/reduces force needed but does little to nothing to effect the edge retention. It doesn't hurt it but it doesn't make it any better than the 8k edge. If you research into the past of sharpening you will find this is not just my opinion but a shared knowledge that dates back hundreds of years.

When I think of sharpening I think of the Japanese, they have not only mastered the knowledge of sharpening but taken it to a prestigious level that goes far beyond just making a sharp edge. In a basic line of thought there is three steps, grinding, sharpening, and finishing. The final stone or Awase To which means final finish is about 8k-10k (note the grit) and a common phrase like "for the sharpest and longest lasting edges" usually accompanies these finishing stones. This doesn't mean this is the best edge for everyone because that's personal preference but I'm not questioning 1200 years of experience.

Coarse vs Fine?
Which one lasts longer will have more factors than just the grit used to sharpen, your skill level and knowledge of sharpening will likely effect your choice along with blade grind, steel, cutting technique, what your cutting, and choice of sharpening method.

My opinion of what holds a edge best is the same as the culture I look to the most for absolute sharpening knowledge. Besides that I select the best edge geometry and finish for the blades intended task. Maybe not the answer you were looking for but its mine and I'm sticking with it ;)
 
knifenut1013 said:
When I think of sharpening I think of the Japanese, they have not only mastered the knowledge of sharpening but taken it to a prestigious level that goes far beyond just making a sharp edge. In a basic line of thought there is three steps, grinding, sharpening, and finishing. The final stone or Awase To which means final finish is about 8k-10k (note the grit) and a common phrase like "for the sharpest and longest lasting edges" usually accompanies these finishing stones. This doesn't mean this is the best edge for everyone because that's personal preference but I'm not questioning 1200 years of experience.
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I have a question about this. When trying to discover grit comparisons across media I've come upon a number of references to the Japanese water stone grit ratings comparable to CAMI numbers. More than one (they may have been extrapolating from the same source material) listed the 8-10,000 grit waterstone as comparable to 2000 grit CAMI specs.
I've always been a little underwhelmed by water stone performance relative to the grit ratings on the stone and this may explain it somewhat (or I might just be failing to understand best practices with water stones). Can you add anything to this?

HH

PS, this may qualify as a hijacking, but haven't we hit our quota of "coarse vs polished" threads for the quarter?
 
230grains said:
Voice your support for high levels of edge refinement vs a "toothy" working edge for retention.
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What about highly refined toothy edges?

I have been learning a fair bit about these in recent months. They are not without merit.

I cannot comment on what holds an edge longer...as I tend to sharpen/refine/touchup/whatever long before the edge would be considered truly dull by most knife users.
 
HeavyHanded said:
I have a question about this. When trying to discover grit comparisons across media I've come upon a number of references to the Japanese water stone grit ratings comparable to CAMI numbers. More than one (they may have been extrapolating from the same source material) listed the 8-10,000 grit waterstone as comparable to 2000 grit CAMI specs.
I've always been a little underwhelmed by water stone performance relative to the grit ratings on the stone and this may explain it somewhat (or I might just be failing to understand best practices with water stones). Can you add anything to this?

HH

PS, this may qualify as a hijacking, but haven't we hit our quota of "coarse vs polished" threads for the quarter?
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Natural waterstones don't have a "grit" as we would normally associate with a scratch pattern and is also why you often see the numbers given in a range. Synthetic stones and abrasives "close" the surface with smaller and smaller scratches until a shine is created, natural waterstones "open" the surface exposing the natural grain of the steel and all it's artifacts. Depending on the steel and as far as I can tell Rc hardness this finishing stone will create one of many effects, on some hard steels or large surfaces it will create a Kasumi finish, softer metals it will act more like a stone and create a 10k scratch, and others it will bring out the grain and leave the Kasumi finish. Kasumi means mist, this type of stone is usually used on the edge of a sword and gives the hardened steel a matte look. Very hard stone too, almost like ceramic.

Fresh 2000 grit sandpaper is closer to a 8k water stone and my awase stone is probably more like 3k paper but the finish between the two would look nothing alike. Standard synthetic waterstones and sandpaper are similar to about 220 grit then the waterstones start making larger jumps in numbers and everything goes out the window again. Waterstones are also much faster at removing metal so a 1k stone seems more like 320 sandpaper.

Technique is huge with waterstones and something that has taken me much time to begin to learn. The hardest part has been learning the stones themselves, then picking the right ones for my liking, and learning how to use them. I'm picky about things like feel and effect of the stone so it was a bit more of a involved process for me but it has payed off well IMO.
 
if i had two identical knives i would sharpen one to about 600 grit and the other to 6000 grit on my edge pro and test it, alas, i don't though. perhaps someone else will and can put this to rest with some evidence?
 
knifenut1013 said:
Technique is huge with waterstones and something that has taken me much time to begin to learn. The hardest part has been learning the stones themselves, then picking the right ones for my liking, and learning how to use them. I'm picky about things like feel and effect of the stone so it was a bit more of a involved process for me but it has payed off well IMO.
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There's a lot to this. I get what I feel are very good results w/ a King 1200 grit water stone, and get OK results w/ my 6000, but cannot get what I feel is good work from my Norton waterstones (1000/4000). They work, but the edges just don't seem to pop. The edges I get from my Arkies are far better. Again, I suspect some of this comes back to certain steels having an affinity for certain grinding media, and some of it must be me - though I get pretty good edges with every other method I've tried.
HH
 
If you are going to try to start an "end of all discussion" thread, you really should have data on both rather than "my polished edge is great" now which is better?
 
I have done a lot of testing on this personally and have come to the conclussion that it depends on the steel, media being cut and how refined or not the edges are.

There really isn't one fit all answer.

In general the polished edge should last longer than the rough edge depending on the steel because the dullness curve will be longer due to the stages of dullness changing.

With the polished edge there is one added stage in the dullness curve from what I have seen in my own testing, not conclusive, but that is what I have seen.

It also takes longer for the edge to really start to break down with the polished edge from what I have seen due to the high refinement and less stress points.

However this won't be seen by most unless they push the edges beyond what normal use would ever be and record the data in testing with the variables reduced to a min.

This will be much more pronounced in the High Alloy, high percentage vanadium steels.
 
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Edges only need to last throughout the cutting job.

Super high polish edges are usually done well ahead of time.

They may or may not last longer then a coarse edge in use, it depends on what you are cutting.

The real question is - how much time do you want to spend sharpening your knives? Are you spending more time refining the edge then you are cutting things? If so you will learn lots about sharpening, but little about real world edge applications.

Butchers and woodcarvers sharpen differently.... and often in ways that make knife nuts cringe..... BUT they get the job done.

There is no be all end all to edges, just different edges and different tasks.
 
Sparljo said:
Butchers and woodcarvers sharpen differently.... and often in ways that make knife nuts cringe.....
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Would you care to elaborate? I have seen many wood carvers sharpen their blades...they (the 20 or so I have seen) use methods similar to how many people on this forum sharpen (and finish by stropping their edges to a brilliant polish). Why cringe?
 
Spar, Yes they do sharpen differently, I know what your saying . As for meat cutters they sharpen to a user edge that will last, more coarse . To around 200g seldom going to the Norton fine India on their Tri-hone 320g . I've been inspecting meat markets for 20yrs. and have yet to see a polished edge among a meat cutter much less the items to bring it to that point . Steels and stones I see and a rare leather strop but no more items than this . DM
 
When I worked for Federal Beef, the really experienced guys would use a triangular file at an angle of about 10 degrees. Then take the burr off on a ceramic rod. Really coarse edge.
I would do mine on paper wheels / ceramic rod. Not quite as rough, and if you were careful (didn't hit your hook) they would last through about 350 shanks.
 
Dm and mongolguy,

Woud you guys think Butchers use a Coarse edge because fixing up a torn down edge is easier with Rougher stones or file?

Not a lot of people know what a Mirror Edge is, and less have seen one in person. Today I encountered someone who called a ~800grit edge a Mirror finish

I don't know what to say
 
Are You assuming right off that Butcher's have a torn down edge and don't know when to sharpen until arriving at that point ? DM
 
No sir.

I was suggesting that a File would restore the edge to a working edge quicker than doing a 5 Step process involving more than 3 Grits
 
he's right, don't assume that ppl who use knives all day long are the best exemple to follow it's just plain wrong.

i'm a pro chef, if i tell you all the misuses, abuses, rough maintenance i've seen along my career ... well you got my point.

my father is a butcher, worked as a meat cutter in a big factory where productivity was the key (they were paid for what they processed) for about 10 years. he is the forst to admit that he knew nothing about sharpening before I got into knives. since then he upgraded his setup and is completely positive about polishing an edge. this allowed him to use shorter knives in average, spend less time sharpening .... with the same swibo knives. no high end steel at all.

most pros see sharpening as a chore, something that slows them down and has to be down as fast as possible. edge quality is a concern, but not the first ... by far. they earn their money cutting not overthinking what's happening when they cut what finish will yield more cuts etc (no offense here)... they focus on their technique first, it's much more effective.

and yes in my experience, for food prep, either on a board or hanging butchering a polished edcge will outlast even the cleanest, burr free, honed coarse edge by a WIDE margin. this is regardless of steel from crap X50CRMO as found in german kitchen knives, to ZDP, cowry, VG1,19c27, aogami, shirogami, niolox, s30v, cpm m4 .... no scientific tests here just use.

but this only applies to food prep. wood cutting/chopping, rope cutting, cardboard cutting .... this i don't know.


ps oh and please before stating that a polished edge can't bite some materials please learn how to sharpen ... an edge is an edge if you can't push cut a tomato with a polished edge don't blame the finish blame your technique only.
 
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xtestifyx said:
No sir.

I was suggesting that a File would restore the edge to a working edge quicker than doing a 5 Step process involving more than 3 Grits
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You bring up an interesting point. To re-gain a "working" edge with a file would take no time at all. The cows were coming in a steady rate of about one a minute, and they didn't stop just because your knife was dull. (God forbid you had to pee) If your partner/s liked you they would help you catch up. But that was not always the case. So the less time you had to spend off the line the better.
 
Yes, I've seen meat cutters sharpen prior to the start of their shift or at lunch and a 100g SiC stone will do it quick . The trick is to remove the burr . Yes, I've cut meat with my coarsely sharpened edge and find it out last the finely sharpened edge and I can slice newsprint or tomatoes easily . This type edge can show good refinement as you say its in the technique . DM
 
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