Polished vs. Coarse edges

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UnknownVT

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Feb 15, 2003
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All other things being equal (like steel, blade geometry, sharpening angle)

A highly polished edge is supposed to be the mark of a sharp knife - hair popping sharp.......

Yet, one reads many reports that a slightly coarser edge that has "micro serrations" - eg: final hone on medium grit stone - seems to give a more agressive cutting edge - eg: in rope cutting tests.

Which type of edge do you strive for, use, and why?

Thanks
 
Depends what I'm sharpening for.

On my larger knives where I know I'm going to be cutting things like rope, tree branches or breaking down large double ply cardboard boxes, I go for quite a coarse edge.
On the other hand, on my smaller knives where I'll be opening small packets, slicing paper, and cutting string I'll put a polished edge on.

Horses for courses.
 
I keep a rather coarse edge on my daily carries, and a polished edge on the knives that see a lot of wood work. I guess I'd have to say that a coarse edge is the more versatile of the two, at least in my daily life.
 
On my "work" knives I have a 20 degree angle and just use the coarse sticks on my Spyderco. On my "play" and self defense knives used for shaving hair, slicing paper, etc. I use a 15 degree angle and will polish the edge up to 6,000 grit...and strop frequently.
 
Good point Bruz.
For me edge angle also goes along with coarse or mirrored.

If it's a coarse edge knife that's going to see a lot of tough action, then I don't feel there is much point putting a very acute edge bevel on it as it will generally roll.
On the other hand, my mirror polished knives will generally be used for push cutting into softer materieals, so an acute angle stands less chance of being rolled (even on the softer steels), and helps with the push cut.
 
Except for extremely long thick blades (like bayonets or machetes) I take all of my edges up to polished razor edges as a initial step. In most cases I then go back for a few light strokes on medium grit ceramic rods to leave a little tooth to the edge. If I expect to be slicing through some tough plastic, leather, etc I might finish with a little coarser edge, say using a 600 grit diamond hone. For a bayonet I might finish using a file.
 
Originally posted by Jeff Clark
I take all of my edges up to polished razor edges as a initial step. In most cases I then go back for a few light strokes on medium grit ceramic rods to leave a little tooth to the edge.
Click to expand...

This is kind of what I also do - for those knives that I re-profile the edge - to a convex edge - I use the strop to get a polished finish -
but then I will use fine (white) crock sticks to finish the final edge.

The reason why I did this was it seemed to me that the strop took/rolled away the final sharpness - this may or may not be actually true - but a final few light strokes on the fine crock sticks seemed to make my knife feel a bit sharper........
 
I generally carry a combo edge knife for EDC, so I polish the plain section as much as possible.

I do have a few plain edged knives that I've started carrying from time to time when I'm not expecting any heavy cutting and on those I generally polish them as much as possible without taking all the bite out of them. I have one I did in O1 that I can't take beyond a soft arkansas stone and a few passes on a strop, shaves hairs off without touching the skin but still has some bite too it. The other is 440C and I usually finish it off with a fine white spyderco bench stone.
 
I prefer the micro serrated type of edge. I usually use a fine(red DMT) stone, and get the edge to where it really bites into my thumbnail. Sometimes, I use the green(ultra fine), but really find that it polishes the edge a little too much for my tastes.
 
I've been playing around with this exact thing. It really depends on the knife.

For my Strider SnG, it doesn't matter at all. It slices cleanly with any edge. I think the mirror edge is prettier, and that's what's on it now. I'd take it camping in this condition.

I have a CS Culloden. It has to be mirror. It drags with the slightest imperfection, but then, it's angle is +/-11 degrees.

My Microtech Tantos liked a mirror edge. My LCC's didn't care.

My Buck fixed Alpha Hunter, didn't care. My Chang Pacific Rim Bowie likes a toothy edge, as long as it is a 'fresh edge.' I think that's because this Bowie is made from 1084.

But get this, the Stanley razor blades for my new Super Knife must first be stropped with white rouge. Even new, they will 'drag.'
 
UnknownVT :

The reason why I did this was it seemed to me that the strop took/rolled away the final sharpness
Click to expand...

Stropping is much more sensitive to technique than using crock sticks. I can get similar sharpness with both techniques, but I have to pay a lot of attention to stropping, v-rods you can do rather mindlessly. If you are skill enough you can freehand the same way.

Watch the Ed Fowler video, he sharpens a knife on a stone, like he is buttering toast, it is so natural. He is also talking to the camera the whole time. Try that the next time you are sharpening. He doesn't go very slow either.

v-rods and secondary edge bevels make sharpening almost trivial. I give them as gifts and all you have to do is make sure that the knives being sharpened have decent relief bevels. I have never heard a complaint about hard to sharpen with such a setup.

-Cliff
 
Like others have said, it depends on use.

My kitchen knives I just touch-up on a steel, when they need sharpening I use a medium stone, then steel. I do keep a couple with a coarser edge, which I get by giving a couple of passes on a coarse stone after regular sharpening.

For cutting rough rope, as for camping projects I use a coarse edge, but I also do decorative knots, for that I like a very sharp polished edge which helps me cut ends cleanly and precisely.

On some knives, including my EDCs, stockman and SAK, I like a very sharp polished edge, there seems to be some kind of obsesive satisfaction in being able to cut a hanging hair.

I get my polished edges by honing on an extra-fine ceramic stone, then stropping, usually on leather, paper or cardboard, I´ve also tryed a polishing nail file with fantastic results, the very fine abrasive plus the foamy backing seem to do the trick.

I like to do double bevels 15/20 degrees, by influence from this forums on some knives I´ve left a single bevel of 15 degrees.

As I´ve mentioned on other threads I use my own homemade jigs holding the stone at an angle an drawing the knife across horizontally.
 
Some alloys seem to suffer when stropped very much with a light abrasive like green buffing compound. For me this seems to happen with high alloy stainless. I think that ductile components of the alloy are getting moved into nooks and crannies between hard carbides. Using white ceramic rods seems to undo the problem. I find that I get a better edge on these alloys when I finish using ceramic rods. When I strop these alloys I only use an unloaded strop. I know that Cliff manages without doing this. I think he uses a more agressive abrasive compound on his strop than ferric oxide (red compound) or chromium oxide (green compound). He has mentioned using silicon carbide which might act more as a cutting compound than a buffing compound.
 
Originally posted by Cliff Stamp
Stropping is much more sensitive to technique than using crock sticks. I can get similar sharpness with both techniques, but I have to pay a lot of attention to stropping, v-rods you can do rather mindlessly.
Click to expand...

That sounds about right - and I'd be the first to admit I am by no means any expert in this -

However because of this apparent rolling away the sharp edge effect that I thnk I perceive - I am pretty careful about stropping - or at least tried to learn a more consistent way.

For example I never strop so that the blade edge becomes close to anywhere near right angles (90deg to the strop).

In fact I was so "paranoid" about this that at one time I found that I was only really polishing the secondary bevel and not the final edge itself.

By trial and error I found that if I can see and feel the rough side's nap rebounding that's about right - (if the nap is not rebounding then I am not stropping the edge) - then I am careful not to cause the blade to go beyond this angle for fear of rolling away/blunting the edge.

I do this by sound on the smooth side - when the cutting final edge is contact with the strop there is a sort of scraping sound - a slight lessening of that angle and the sound goes away - more then the there's a danger that the blade's edge may actually start to cut/marr the leather.


So although I do not consider myself an expert - I think I am being pretty careful and consistent about my stropping.

I can examine the edge with a 30x illuminated microscope, so I can see my progress - for example I got rid of the flats from my ATS-34 small Sebenza from cutting that dirty sisal rope from the footmat - by using the crock-sticks (fine white) then stropped to polish the final edge.
(actually I stropped first to see if I could get rid of the flats - it did not, and I merely polished away the scratches on the secondary bevel face...... I had to use the crock-sticks to get rid of the flats)


Originally posted by Jeff Clark
Some alloys seem to suffer when stropped very much with a light abrasive like green buffing compound. For me this seems to happen with high alloy stainless. I think that ductile components of the alloy are getting moved into nooks and crannies between hard carbides. Using white ceramic rods seems to undo the problem. I find that I get a better edge on these alloys when I finish using ceramic rods.
Click to expand...

Now this makes some sense to me - as most of my knives are stainless steel - with the most used/sharpened being a Victorinox SAK - like Jeff I found that if I carefully hone the knife with the last step being the fine white crock-sticks (V-hone) - then if I strop I seem to lose some sharpness - eg: hair shaving - but a few (like only 3 each side) light strokes on the fine white crock-sticks will make the hairs jump off........

Perhaps my stropping technique is just not good enough -
but I cannot figure out how to be better at it - so far ........

So any advice will be gratefully accepted.
 
A couple of other ways in which I get pretty good stropping results:

1.- Wrap a piece of paper (I use non-glossy calculator paper) tight around a ceramic rod and strop as if steeling spine first (backward steeling), probably the very fine abrasiveness of the paper with the high pressure of a single point on the edge is what gives the results.

2.- Wrap a piece of paper tight around a hone and lay it on my inclined plane jig, then stropping with the knife horizontally spine first (downward), I feel this gives a precise angle, stroping at the same angle as the bevel and practically no give on the surface (thin paper hard backed by the stone), this polishes the whole edge (or secondary bevel) evenly.

Another comment on coarse edges.- For a soft steel knife a coarse edge makes it more usable than a polished edge (or usable for a bit longer) I do coarse edges on cheap kitchen knives and on cheap knives used on rope.
 

Watch the Ed Fowler video, he sharpens a knife on a stone, like he is buttering toast, it is so natural. He is also talking to the camera the whole time. Try that the next time you are sharpening. He doesn't go very slow either.
Click to expand...

AND, his Norton stone is on a fairly uneven surface, so while he's talking and sharpening, the stone is rocking around. Then he takes a sheet of paper and shows how sharp it is.... Argh. How do people do that?

I use my Edgepro, and highly polish the edge. Unlike other folks, for me, the highly polished edges push cut AND slice better - and last longer. Maybe I'm doing something wrong with the gritty edges, I don't know.
 
There are all sorts of possible reasons why stainless steels with large carbides could not respond well to stropping, carbide tear out was what I wondered about. It would be nice to check the edges under high mag and see how they changed.

I however have not had a problem in getting a very fine polish on any stainless with a suitable edge geometry. Including the ones with poor reputations like ATS-34 and the like. I have brought these up to free standing arm hair sharpness.

When grinding the edge I make sure that the difference in the finish before the stropping isn't too far removed from the strop polish. 1200 DMT or finer if possible, 4000 AO, or 5 micron SiC. The stropping should be only a few passes.

You lose aggression quite quickly after this, though push cutting ability can still grow. I did some comparisons of this nature in some of the older reviews :

http://www.physics.mun.ca/~sstamp/knives/vision.html

It should also be mentioned that steeling an edge will act to increase sharpness by smashing out the edge into a very fine layer.

JJ of Razor Edge illustrated this with pictures of the edge showing the effect of steeling. I have constantly seen steeling make an edge sharper (after use) than it was after just freshly honed - however it is weaker and will blunt faster.

Ceramic rods have a similar effect, though not to the same degree as smooth steels as they are abrasive as well as adhesive.

-Cliff
 
this evening I stropped an Opinel #8 Inox, with pretty good results, perhaps it was because I did something different.

Because the face of the blade was looking "tired" dingey I stropped the face of the blade to bring back some of the polish and only lifted very slightly toward the end of the strop stroke - basically I was trying my best to follow the convex contour of the blade face.

The blade looked pretty nice after this strop polish and I thought I'd try and test the edge - it turned out to be "whoa!" hair popping sharp - almost like that the hair would jump off merely showing it the blade's edge :D

Thinking this might be a fluke - I did the same with another Opinel #8 Inox - with the same results.

Can some of you who strop successfully please advise on the correct way to strop with a regular leather (hanging) strop?

Does one actually just lay the blade face flat on the strop and pull from spine to edge without any lifting of the spine - relying only on the flex of the leather to wrap/roll round the edge?

I've always lifted the blade's spine to hear a sort of scraping sound and see the rough side's nap rebound. So have I been stropping incorrectly, and actually have been raking the edge and blunting it?
 
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