Polished vs toothy edges

I

i_am_ninja

Joined
Nov 28, 2008
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103
Hey guys, I've been noticing an interesting aspect to my self-sharpened knives, which has to do with the way the edge behaves.

I use the lansky 5-stone sharpening system with a Cr2O3 strop, and 1 out of 3 times I can get my blades to shave a hanging hair, so I think I'm getting them pretty sharp, but theres an a catch... It feels like my edges have zero bite. I'd say all my blades fail the fingernail test and despite the ludicrously sharp edge I get right after sharpening, but my blades seem to dull pretty quickly too, which makes sense for a toothy edge, but not so much with a polished one.

I've noticed that belt-finished edges from the factory or from my local shop have much more bite, despite them not being as good at pushcutting and shaving hairs, and I was wondering how I could replicate that with my system. Do I just finish with a coarser stone and strop from there? Or does it have to do with the convex edge?

Any helpful info would be appreciated.
 
 
I like a good amount of bite for my folders. I usually stop at 1200 grit (Japanese grit JIS) and strop with 6, 1, .5 micron pasted strops. This gives a very sharp but slightly toothy edge.

My advice would be to try out different combinations. Stop at one lower grit and strop. Next time lower it again. See what you like.
 
Thanks for the info. In terms of durability though, does a toothy edge hold up better? or does a polished one?
 
i_am_ninja said:
Thanks for the info. In terms of durability though, does a toothy edge hold up better? or does a polished one?
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Depends entirely on the steel the blade is made from, the heat treat of said blade, cutting edge angle, and the material you are cutting. It's also covered in detail in those threads. ;)
 
I also use the lansky and for softer steels like 8cr13mov and others alike. I stop at the 600 fine stone, then hit it a couple a times on my super super fine ceramic rods. I don't know the grit or brand my pap gave them to me, but they're smooth as glass and do an amazing job at touching up an edge thats still sharp enough to work but considered dull to most. Then i strop the tiny bur off with a "fine" compound as stropman.com says, they don't give a specific, and I get a ton of bite and a hair popping edge and with 8cr especially for me its a great combo. I find it holds an edge for a decent amount of time for edc purposes. After this treatment all I do is go to my ceramic rods till the edge becomes polished over time then I rough it up again doing all this.
 
Roughing the edge up isnt something I've heard before but it makes a lot of sense.

Also to revdevil, is there a certain steel property that fits toothy/polished edges? I could see hardness as a plus for polished and grain structure for toothiness but idk anything farther than that. To clarify this is for my 940 and pm2.
 
Depends on what you call polished and toothy and what you are doing. For a standard CATRA test, 8000 and 600 grit total edge life was generally within 5%.
 
kreole said:
There are lots of threads of opinions on the subject. Here are a few:

http://www.bladeforums.com/forums/showthread.php/725090-quot-Toothy-quot-Edge-vs-Polished-Edge

http://www.bladeforums.com/forums/s...-in-a-smooth-polished-edge-vs-Toothy-polished

http://www.bladeforums.com/forums/showthread.php/260194-Polished-vs-Toothy

http://www.bladeforums.com/forums/showthread.php/756561-Polished-edge

http://www.bladeforums.com/forums/showthread.php/945339-Polished-edges

http://www.bladeforums.com/forums/showthread.php/829701-toothy-edges-work-great

http://www.bladeforums.com/forums/showthread.php/779077-Mirror-Polished-Edge

http://www.bladeforums.com/forums/s...e-retention-and-use-vs-quot-working-edge-quot


There are also a few on specific steels.
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Folks sure seem to be divided between toothy and polished.

Myself, I never had or used a polished edge. I've recently learned how to sharpen, and now get my Spydercos sharper than from the factory. I guess the next step will be to learn how to polish. For now, I'm happy having sharp knives.
 
singularity35 said:
Coarse edges usually cut better, polished edges look better. :D
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Gotta agree with this one. A polished edge is rarely better for me.
More aggressive knife edges seem to be better for most stuff in my work environment.
I need polished edges on my chisels and plane irons, but not my knife. I'm weird, though... do it on my knife most of the time anyway.
 
It is tough, because polished edges are so sexy. But the edge off a 1200 diamond plate is an awesome cutter. Once the edge is sharp, cutting performance takes the next big jump by thinning the bevel behind the edge.
 
Wet Noodle said:
Gotta agree with this one. A polished edge is rarely better for me.
More aggressive knife edges seem to be better for most stuff in my work environment.
I need polished edges on my chisels and plane irons, but not my knife. I'm weird, though... do it on my knife most of the time anyway.
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Yeh, when I don't expect a lot of cutting, I'll take the loss of performance of a polished edge because I like the way they look. It's different when I know I'll be cutting a lot of material, I'll microbevel with a spyderco medium or fine then.
 
Technically, and practically, if one sharpens the edge properly, polished edge is sharper, thus it cuts better. Both are simple physics, finer abrasives give more refined edge, and generated pressure is proportional to the area in contact, in other words, less force is needed to generate the same pressure with sharper edge.
Edge durability is a different question.
I can sharpen kitchen knife with 0.1mic grit diamonds (around 150K) so that it cuts tomato under its own weight, zero horizontal movement, but I've never been able to repeat the same feat with even 10K finish, which is already bright mirror polish, let alone 1000 grit or lower. Yeah, that kindda edge doesn't last too long, but still.
Plus, for push cutting polished edges do better, and last longer too.
 
Gator97 said:
Technically, and practically, if one sharpens the edge properly, polished edge is sharper, thus it cuts better. Both are simple physics, finer abrasives give more refined edge, and generated pressure is proportional to the area in contact, in other words, less force is needed to generate the same pressure with sharper edge.
Edge durability is a different question.
I can sharpen kitchen knife with 0.1mic grit diamonds (around 150K) so that it cuts tomato under its own weight, zero horizontal movement, but I've never been able to repeat the same feat with even 10K finish, which is already bright mirror polish, let alone 1000 grit or lower. Yeah, that kindda edge doesn't last too long, but still.
Plus, for push cutting polished edges do better, and last longer too.
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Right, but that is assuming you are only push cutting. Try slicing through zip ties or thick plastic bags with a polished edge versus a slightly toothier edge. I think you'll find the toothier edge performs better. Lately I've been polishing my bevels, but adding a very small toothier microbevel with a medium spyderco ceramic and the performance has been outstanding. With proper technique and a light touch you can still produce edges that effortlessly whittle hair but also slice like the dickens with much more bite than a polished edge.
 
The idea of microserrations just seems sketchy to me for anything harder than meat. It's only steel, and we're talking about steel about foil's thickness if not less. Those serrations just sounds like they would break off into wood almost immediately.
 
i_am_ninja said:
The idea of microserrations just seems sketchy to me for anything harder than meat. It's only steel, and we're talking about steel about foil's thickness if not less. Those serrations just sounds like they would break off into wood almost immediately.
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Ok, so how do you explain the aggressiveness of a coarse edge? It will also keep it's bit longer than the polished edge.
 
I'd guess the edge stays aggressive while the coarse profile wears unevenly and creates new 'teeth' until the radius of the edge reaches a point that the steel doesn't fracture as much and wears like it would with a polish.
 
hardheart said:
I'd guess the edge stays aggressive while the coarse profile wears unevenly and creates new 'teeth' until the radius of the edge reaches a point that the steel doesn't fracture as much and wears like it would with a polish.
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Yeh, that sounds about right.
 
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