Polished or coarse? A question of edge types.

K

Knifeclerk

Joined
Jul 16, 2004
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I am having a hard time figuring out practical areas where a polished edge wil excell over a coarse edge. Second of all, I have been drinking, so please excuse any typos/grammatical errors.
Plastic. Cardboard.
These are what I cut most often. I find that a coarse edge is better for such things. But I use ceramic rods and strosp to put a polished edge on all my knives. why am I waisting my time? Give me areas where a polished edge is better than a coarse one. Practical, not so much, it doesn't matter. Skinning? Shaving? spreading creme chease? Find me a reason to keep my fine rods for my Sharp Maker!
 
For about 27 years I was a machinist. In the course of a day I would cut alot of things with a pocket kknife in the shop. Dirty fiber tape off round stock, cardboard, masking tape, plastic double sided tape, thin 1/8 or 3/32 rubber mat. I always kept a course edge on my knife using the little ez-lap diamond rod that looks like a small pen. A polished edge under abusive conditions breaks down too fast. And a course edge can be restored with a half dozen swipes of a coures diamond hone. I also used a knife I did not care about- a Gerber LST. Not a bad little knife, but not one to love like my sak, or one of my good stockmen. If I wore it out in 3 or 4 years, no big deal.

Course edge, cheap knife. Good work combo.

Now I'm retired I like very sharp, stroped edges.
 
Get a good serrated edged knife for all around usefulness. I like the Spyderco "Rescue" model. It has a sheepsfoot 93mm serrated blade with tons of cutting edge.
 
I do a little bit of wood carving and whittling. A polished edge is far superior to a toothy edge because you push your blade through the wood, severing the fibers rather than "sawing" through them. This gives you a nice smooth finish on the wood rather than a "fuzzy" finish.

So I put a mirror-polished edge on my carving knives and pocket knives when I am using them for whittling. I put a mirror edge on my chisels and gouges as well. I strop often while carving - every couple of minutes and whenever I am contemplating my next cuts.

I use my EDC knives for general yard work, cutting cardboard, opening boxes, etc., and, like Knifeclerk, I prefer a toothier edge on them so I sharpen on medium grit rods, knock the wire edge off and into the pocket they go.
 
It's kinda funny, because I know a more coarse edge is probably better for harder use, but I still like being able to see just how razor sharp I can get my knives.That said, for work I use a serrated blade(D'Allara Rescue) but for EDC I try to keep my PE Mini Stryker as highly polished as possible and I find it does very well for general use. If I were to use that one knife(the BM) for work and EDC, I would probably have a more coarsely sharpened edge.
 
mycroftt said:
I do a little bit of wood carving and whittling. A polished edge is far superior to a toothy edge because you push your blade through the wood, severing the fibers rather than "sawing" through them. This gives you a nice smooth finish on the wood rather than a "fuzzy" finish.

So I put a mirror-polished edge on my carving knives and pocket knives when I am using them for whittling. I put a mirror edge on my chisels and gouges as well. I strop often while carving - every couple of minutes and whenever I am contemplating my next cuts.

I use my EDC knives for general yard work, cutting cardboard, opening boxes, etc., and, like Knifeclerk, I prefer a toothier edge on them so I sharpen on medium grit rods, knock the wire edge off and into the pocket they go.
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Good input. For push cutting you can't beat a polished plain edge.

http://www.drsharpening.com/leatherhone.html

There are basically two kinds of cutting, push and slice. Most of the cutting I do is slice and the serrated edges work the best.
 
yes as DGG said the difference is not hard vs. soft usage, it is push cutting vs. slicing. That is why polished edge is much preffered for wood carving and whittling, also for "extreme" push cutting better known as "chopping "- thus axe edge and big chopping blades like kukri prefferably have polished edge as well.
 
Interesting. Thanks for the input. So would I be right in assuming that a coarse edge would hold up better for skinning?
 
A smooth edge holds up better than a coarse edge in all applications, but that doesn't mean that it will cut better for a longer time. I guess it is sort of a function of what you mean by "hold up". I assume that you are talking about not losing material from the edge, having the edge fold over, chip, ding, or otherwise developing a more obtuse edge profile. In that technical sense a smooth edge will hold up better.

On the other hand for a lot of slicing applications a coarse edge may be effective longer. The microserrations of a coarse edge will continue to bite into rope even when the edge loses some material and is theoretically more obtuse. Another thing that can happen is faster wear on a smooth edge due to higher cutting pressure applied in an effort to get it to slice through tough material. You basically may push the edge harder because it doesn't want to bite into the materials that you cut frequently.

I am an old proponent of a rough finish on rather thick-edged blades. I would often use a file to sharpen a bayonet or a machete. I used to finish many of my pocket knives with a medium ceramic rod. I have gone away from this. I find myself doing less slicing work in recent years. I also keep running into people who want to see how well my knives can shave. I mostly go for an extremely smooth razor edge. If I need better slicing I go back and slightly roughen the edge with my Sharpmaker fine ceramic rods. If I am doing dozens of knives in a row I finish them with the medium ceramic rods.
 
Jeff said...
"the edge with my Sharpmaker fine ceramic rods. If I am doing dozens of knives in a row I finish them with the medium ceramic rods.
"

Is that because it takes les time, or is a better edge finish for general tasks?
 
Anyone compared the "toothy" edge produced by
a) a coarse stone.
b) a coarse stone followed by stropping. And
c) A polished, push-cut edge that is then given an edge trailing stroke or two on a sharp diamond plate or something to add some tooth to an already sharp blade?
 
Re db's question about my mass sharpening finish. The answer is that it is a speed issue. When I sharpen knives for the local Marian House Soup Kitchen they are usually thrashed. They need extensive reprofiling to get decent performance. That involves removing a lot of material and that takes a lot of time when you are working on over 50 knives (even when you use a belt sander for most of the work). If I am pressed for time I don't reprofile to as low an angle as I would prefer (about 10 degrees per side) and that reduces cutting performance. If the knives were segregated into meat cutting knives and vegetable knives I would put coarse edges on the meat slicers (maybe a 600 grit diamond finish) and smooth edges (fine ceramic rods) on the vegetable dicers. Since they get picked up and used randomly I put a compromise edge on everything of medium ceramic rods. So on kitchen knives that are back-beveled to somewhere close to 15 degrees I put a medium ceramic finish on the edge.

My own kitchen knives are profiled much thinner and I usually leave the edge with a fine ceramic finish for meat cutting and an ultra-fine ceramic finish for dicing vegies.
 
Jeff Clark said:
The microserrations of a coarse edge will continue to bite into rope even when the edge loses some material and is theoretically more obtuse.
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I never thought of it from that perspective, looking at loss of metal rather than reduction in performance. It would be interesting to do a long term study and see which one wore out the edge faster assuming no oversharpening which tends to be more of a problem for really coarse finishes.

yuzuha said:
Anyone compared the "toothy" edge produced by
a) a coarse stone.
b) a coarse stone followed by stropping. And
c) A polished, push-cut edge that is then given an edge trailing stroke or two on a sharp diamond plate or something to add some tooth to an already sharp blade?
Click to expand...

Yes, one of the early reviews took an x-coarse edge, did some work and then stropped it on CrO and noted the influence it made after every few passes. Essentially what happens is that there is a gradual loss of slicing ability and gain in push cutting.

However if you freehand the c-coarse edge sometimes the initial stropping can increase both slicing and push cutting performance as it makes the edge more uniform, but with a jig or v-rod there isn't any benefit, I would suggest simply use a more suitable end finish.

A polished primary bevel is of little use, the effect of drag is very slight compared to the other forces (wedging and direct rupture at the edge) on most media. Some argue that the coarse scratches on the sides of the bevel aid in cutting but I don't see being significant either and it is trivial to test.

-Cliff
 
I've found that coarse scratches on the sides of the bevel tend to collect more dirt/sticky stuff than a polished edge bevel.I don't know if this effects cutting at all or not but it's alot easier to clean a polished bevel that is for sure. I don't notice any difference from a coarse edge put onwith or without polishing the bevel other than the time it takes to do it.
edited to ad...
Stropping a coarse edge I've found can clean or aline a little but only take 1 stroke per side. if you take more than that or use compound you will start to smooth out the coarseness.
 
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