Coarse vs. Fine Stones For Finishing an Edge?

Handwrecker

Handwrecker

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May 4, 2010
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After reading this thread, I've started to wonder about what would make the most aggressive and lasting edge for these newfangled high-alloy super steels. I'm curious about M390, S30V, and 20CP mainly.
http://www.bladeforums.com/forums/s...-that-much-anymore-to-keep-my-knives-in-shape

The general consensus seems to be that finishing with a slightly courser medium provides a better edge. Is it better in that it cuts more aggressively? Will it deterioriate faster than a highly polished edge?

I currently use my Sharpmaker with UF rods to finish my edges, but am considering using the brown stones aster reading that thread. Any input about this is greatly appreciated. Thanks!
 
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It depends on the material you're cutting. Some fibrous material like rope can be cut easier with a coarse edge, though I've rarely had the need for it. As far as the new super steels, I believe grain refinement of the carbides ultimately determines how long your knife can hold that razor edge. In my experience, Elmax and M390 can hold a razor edge for a very long time even when cutting cardboard.

It's hard to say precisely whether a coarse edge stays sharper longer. It might only seem that way since some steels like S30V or D2 will lose that razor edge in a few cuts. I suppose you could ask Ankerson to try his rope cutting with the same knife using two different finishes and see if one lasts longer than the other;).
 
Handwrecker said:
After reading this thread, I've started to wonder about what would make the most aggressive and lasting edge for these newfangled high-alloy super steels. I'm curious about M390, S30V, and 20CP mainly.
http://www.bladeforums.com/forums/s...-that-much-anymore-to-keep-my-knives-in-shape

The general consensus seems to be that finishing with a slightly courser medium provides a better edge. Is it better in that it cuts more aggressively? Will it deterioriate faster than a highly polished edge?

I currently use my Sharpmaker with UF rods to finish my edges, but am considering using the brown stones aster reading that thread. Any input about this is greatly appreciated. Thanks!
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That depends. :)

I have done some testing on this using a few knives with different edge finishes and found that the best balance of edge retention and cutting ease is someplace in the middle of coarse and polished and that will depend on the steel what that will be.

Like I always say there is always a balance that has to be met, to get some thing we have to give some thing else up.

In general that balance for best cutting performance and edge retention seems to be around the 45 to 30 Micron level in cutting rope and cardboard.

What I have found in my testing that a non polished edge (45 to 30 Microns) will slice with a lower amount of force than the highly polished edge will and continue to to cut with a lower force for a very long time.

Manila Rope is a good test media for this making slicing cuts, if the edge is too coarse it will just drag with too much force and if it's too refined it will want to slide more and take too much force while someplace in the middle will just slice right down through it with min effort, the difference in cutting force can be as much as 5 LBS on rope from my testing.

That said some steels will cut more aggressively than others due to higher Carbide content so with those types of steels the edge could be able to be refined slightly more than the lower alloy steels.

The best answer is try the different edge finishes and see what works the best for you and how you use your knives, you can taylor the edges to suit different needs.
 
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Ankerson, How do you sharpen your Para 2's in s90v and cts 20cp for EDC ? What do you think is the best edge finish is for general purpose cutting in your experience ? Thanks, Kurt
 
kurt6652 said:
Ankerson, How do you sharpen your Para 2's in s90v and cts 20cp for EDC ? What do you think is the best edge finish is for general purpose cutting in your experience ? Thanks, Kurt
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Sharpened them on the Fine Norton Sil Carbide stone and lightly stropped to remove the burrs.
 
Ankerson, Some here have slammed and mocked me for posting these same type findings. I doubt they will do the same toward you. So glad you posted this as my findings echo yours. Thank you, DM :)
 
David Martin said:
Ankerson, Some here have slammed and mocked me for posting these same type findings. I doubt they will do the same toward you. So glad you posted this as my findings echo yours. Thank you, DM :)
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I am not sure why they would mock you....

As long as the edge is crisp and clean, burr free it will very extremely sharp.

I still remember back when I was young and used oil stones, mostly some thing around 400 Grit for a finishing stone if i wanted to refine the edge more than the Med Stone.

Or sharpening a knife on a Sil Carbide Puck with no lube at all in mins and it would shave hair like nothing.

No real need for a super refined edge just to get it sharp, take the edge right off the stone and strop it to remove the burr and it's good to go.
 
I'm a big fan of DMT's, but not exclusively. I generally go for the DMT blue when the knife is dull dull, or the red if it's just dull. ;) If I have time, I like to finish up on a ceramic stone, no real reason why, I'm really partial to ceramics and the edge that they leave. My favorite are the Spyderco ceramics. I've had some real quality issues with Fallkniven ceramics, I might have to send one back in...

If I really want to show off, I drag out my EP and put a mirror edge on the blade. It works well, but I mainly choose it for aesthetics.

Personally, I don't see a whole lot of difference in edge holding when I finish with diamonds, ceramic or the mirror polish. I will also freely admit I haven't really done much testing either. The mirror edges doesn't slice rope quite as well, but it does work. My main motivation in the type of edge I put on is how much time I have to sharpen, not what kind of edge I'm looking for. I don't have much free time (busy family), so I sharpen with the time I have available. I'm not that motivated to argue which one is better, I think DM and Ankerson have put a lot more into the testing of this sort of thing, I'm happy to take their word for it.

I put in enough time honing my straight razors, that satisfies most of my desire for polished edges. :D
 
Handwrecker said:
The general consensus seems to be that finishing with a slightly courser medium provides a better edge. Is it better in that it cuts more aggressively? Will it deterioriate faster than a highly polished edge?
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Polished edges are better for push-cutting; coarse edges are better for slicing. Take a saw blade, if you try to push-cut with it you will get poor results and will damage the teeth but if you slice with it you get the job done without damages. According to the stuff you have to cut you have to choose your final sharpening grit. However, an edc knife used for very different tasks will see a mixt of push-cutting and slicing in the same time. So, like says Ankerson, it's a compromise you have to find.

I work my edges the way Sodak does. DMT coarse, fine, Xfine or XXfine, then a very smooth ceramic stone. Whatever is the final sharpening grit i strop the edge just enough to remove weak teeth and align strong teeth, see it as an "edge cleaning".

dantzk.
 
I posted this in the other thread, just a little test to try. ;)

For anyone who doubts what we are saying I have a simple test for them to try. :D

Take a paper towel and try and slice down through it lengthwise with a polished edge and see what happens.

Then do the same thing with a coarse edge.

This is taking into count that both edges are very sharp to start with.

Could be a real eye opener for some. ;)
 
And while you have TP not too far from you go from tip to ricasso after a quiet stab in the middle of the sheet with a coarse edge, look at the result and then do the same with a polished edge.

dantzk.
 
I used to obsess over how sharp I could get my knife, but as I got older, I got burned out on the whole sharpening thing, and went back to my boy scout days. We used a plain old gray carborundum stone, and a light stropping, and we had sharp knives. These days I use a course stone, and that's it. Life's too short for obsessions. I'm only interested in what works, and I find a course stone puts on a good sharp edge, and it lasts better than a hair whittling super duper samurai legend edge. Rope, twine, fish bellies, plastic packages, UPS boxes, course edge works great, and when it does get dull, it can be restored in a few minutes anywhere with a little pocket hone. Since I'm not shaving for a living, nor doing surgery, I do not need a micron splitting edge. But when I'm out in the garden and need to cut jute twine, or the UPS guy drops off a box and I'm slicing cardboard, I like the course edge for it's bite.

David, I've read your testing, and I applaud both your effort and results, and agree with you 100%. Of those who mock or flame you, some people cannot handle the truth. The heck with them.

Carl.
 
jackknife said:
I used to obsess over how sharp I could get my knife, but as I got older, I got burned out on the whole sharpening thing, and went back to my boy scout days. We used a plain old gray carborundum stone, and a light stropping, and we had sharp knives. These days I use a course stone, and that's it. Life's too short for obsessions. I'm only interested in what works, and I find a course stone puts on a good sharp edge, and it lasts better than a hair whittling super duper samurai legend edge. Rope, twine, fish bellies, plastic packages, UPS boxes, course edge works great, and when it does get dull, it can be restored in a few minutes anywhere with a little pocket hone. Since I'm not shaving for a living, nor doing surgery, I do not need a micron splitting edge. But when I'm out in the garden and need to cut jute twine, or the UPS guy drops off a box and I'm slicing cardboard, I like the course edge for it's bite.

David, I've read your testing, and I applaud both your effort and results, and agree with you 100%. Of those who mock or flame you, some people cannot handle the truth. The heck with them.

Carl.
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You can take that one step farther and strop that edge a few times (Like 4 times) with green compound and you will have dangerously sharp edge that will slice like crazy because it's still toothy.

A coarse edge base then straight to a strop will leave one heck of an edge.
 
Ankerson said:
You can take that one step farther and strop that edge a few times (Like 4 times) with green compound and you will have dangerously sharp edge that will slice like crazy because it's still toothy.

A coarse edge base then straight to a strop will leave one heck of an edge.
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I give it some stropping on the back of my Dickies work belt. It seems to be effective, and it goes through jute twine and sissel rope like nothing.

Carl.
 
An edge for a purpose. You wouldn't use the same knife to baton firewood and prepare sashimi, so why would you reasonably expect the same edge to work for all applications? :D

For fillet knives, skinning knives, or knives used for kitchen slicing, I generally have been running a worn 320 belt, then a few passes on a SurgiSharp leather belt loaded with green compound. It seems to be very close to the factory edge on most decent knives, and makes people very happy with performance and longevity. Bearing in mind that most people are used to the edge retention and sharpness of a WalMart standard factory edge as their 'high end' point of comparison. It's a very quick edge to put on.

For whittling knives, kitchen knives used for chopping, fish cleaning knives and stuff like that, I continue the grit progression down through a 9u belt, then polish with the leather and green compound, then another leather belt with white compound. It leaves a very nicely finished edge that doesn't have much "tooth" left in it, but performs admirably well in push cuts.

I guess my point is "use the edge for the task at hand." My own knives are retained with their factory profile (V-bevel or convex) and polished highly. V-bevels get the EdgePro treatment, convex get worked down on the fine belts, then leather and compound.
 
I have a few thoughts in this direction - came to the conclusion that a coarse edge stropped with a coarse grit will make for an extremely efficient draw cutter. The larger grit gets between the "teeth" and clears out any burr without smoothing out the scratch pattern. I've been advocating this technique to anyone who displays the least interest since I stumbled across it about a year ago - my current EDU is sharpened on 220 grit sandpaper and stropped on 220 SiC powder (reel mower sharpening compound). Pushcuts newspaper easily, still has a lot of bite, and can be quickly touched up without using a fixed abrasive (stone, sandpaper).

HH
 
Yet another reason I kick myself for loosing that old Schrade stockman. Sheepsfoot blade was about 7 degrees per side, with a high polish, clip blade was in the middle, say 17/side with a Spyderco Medium finish, and the spey blade was 22 with a 220 waterstone finish. Now if I could just find one made with different steels for each blade.

I still need to try that coarse stropping stuff. I also need to go back and put a really coarse edge on my Cold Steel Kudu. It seemed to work best with that kind of edge. The soft steel provides a backwards sharpening experience. The coarse edge takes longer to put on, since the burr is much more stubborn to remove. Shaping the edge is quick and easy, honing and burr removal make it take as long as a polished edge. In the end, a coarse edge with only one grit step on soft steel takes just as long as a fine edge with 220/1000/Brown/White Spyderco ceramic (Sharpmaker). And in the end, both will split a beard hair held between my fingers.
 
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jackknife said:
I give it some stropping on the back of my Dickies work belt. It seems to be effective, and it goes through jute twine and sissel rope like nothing.

Carl.
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Yeah it should go through rope like it's not even there with that kind of edge, makes a nice crunching sound when cutting it too. :D
 
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