What type of edge dulls sooner: toothy or polished?

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Whisper21

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Jun 11, 2013
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Wouldn't a toothy edge, with its micro serrations, bend and begin to dull the edge sooner than a polished edge without teeth?
 
My experience leads me to agree with you, Whisper - depending on the steel you are sharpening. Some steels like a polished edge, others, not as much. But I greatly prefer the refinement of a polished edge for my uses.

However, this is somewhat of a "holy war" question among sharpening fanatics. You'll find a lot of folks with positive experiences in both the "toothy" and "polished" camps.

TedP
 
It's the steel, the angle, and the hardness. You cannot change the wear resistance of a steel by the grit you sharpen it to.

Using the wrong edge type for the task can effect how it performs in that task though. You don't want to use a high polished edge to cut fibrous materials and you wouldn't want a coarse edge for cutting fish or chopping wood.
 
Just to be clear, let's specify more specific(theoretical simplication per see) edge type & geometry:

Sample blade: 10cm of cutting length and start with a perfect apex with bevel at 30* inclusive, apex at 1um (easy round #)

1. a perfect apex, i.e. absolute perfect smooth/polished edge.

2. make toothy by removing equal lateral triangular wedges from the bevel, thus only the top of the teeth are sharp.

3. take #2, sharpen the teeth, turn the edge into a saw. Where each tooth has same bevel height, so angle will go from 30* from the peak to obtuse at the trough (depend on the tooth height).

Also let's not count false-edge (envision a perfect square top spine which as 2 90* edges).

Without much thinking #2 really ony has small percentage of sharp edge and the rest is dull, hence dull is guarantee.

#1 has 100um^2 worth of steel with 30* inclusive bevel.

#3 has 200um^2 worth of steel with bevel angle from 30* to 60* inclusive, since each tooth is thinner at the top and thicker at the bottom.

Addressing OP's question without taking edge cutting task|style into consideration. In most cases, #3 is more durable than #1 and #2.
 
I have taken lately to toothy edges. I cut a lot of carboard at my shop. Most all of this, is triple thick, heavy duty stuff. My refined polished edges, seem to always dull quick. My toothy, but shaving/push cutting sharp edges, seem to slice through it not only better, but longer for me. This I guess, really depends on what you are cutting. YMMV

This is a great hobby, and we all enjoy it! One of the cool things I am learning as I go, is being able to make a knife be able to do several different things, depending on how I grind it.
 
I would imagine that a smooth, non-toothy edge would maintain more acuity at the apex in the longer term.
 
Blunt .. so this is a new way of looking at the apex .. interesting!

Since achieving #1 is what I can do to the closest with abrasive I have, then # 1 is what I aim .. ;)
 
My own working theory, and I have no solid evidence for this but -
A coarse edge will outlast a polished one if drawcutting along the blade is the primary usage.
A polished edge will outlast a coarse one if pressure cutting or chopping is the primary usage.

Coarse edge carries far more friction into the cut = less pressure when drawn, more pressure needed when pressed or chopped.

Polished edge carries far less friction into the cut = less pressure when when pressed or chopped, more pressure needed when drawn.

Pressure seems to be major killer of edges, contact with abrasive materials notwithstanding.

This is a general observation and there are certainly other factors, but in general I find this to hold true much of the time. The answer to the question is another question - What are we cutting?
 
Chris "Anagarika";12473909 said:
Blunt .. so this is a new way of looking at the apex .. interesting!
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Night owling eh Chris! Taken angle of impact into consideration, serration is superior to plain edge - big time. I like plain edge for ease of sharpenintg, couple with push cut... more fun to use knives.
 
HeavyHanded said:
This is a general observation and there are certainly other factors, but in general I find this to hold true much of the time. The answer to the question is another question - What are we cutting?
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Everything. When cutting everything, would the toothy or polished edge last longer? Appropriateness aside.
 
Whisper21 said:
Everything. When cutting everything, would the toothy or polished edge last longer? Appropriateness aside.
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When cutting everything, an edge in between coarse and toothy will outlast either. Approx 1200 - 4k JIS, or 600-1000 ANSI.

Edit to add: My personal theory is that anything below or above those numbers (taking into account finishing techniques, steel types, edge characteristics specific to certain abrasives) qualifies as "specialty" edge - its been sharpened for a specific primary task.
 
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To the naked eye, almost all of my edges quickly take on a somewhat more polished look. But, that 'polish' is likely at the lower end of the mirror/near-mirror range, likely equivalent to something between 1000-2000 grit FEPA-P. I use wet/dry sandpaper quite a lot, followed by stropping, which polishes further (and stropping with black & green compound on wood and/or leather accounts for probably 90% of my edge maintenance). Even coarser grits of the sandpaper, like 400-600 or so, become more fine with use, and that's why my edges all eventually take on a near-mirror finish after touching up on that paper. All that aside, when my edges are finished as such, I've been very happy with how they perform and hold up.

I often re-bevel or set a new convex on 320-grit sandpaper, which after stropping on 600-grit SiC and green compound, very quickly starts refining to a somewhat higher finish. The 320-grit seems like a good/very good jumping-off point; cuts very well, especially with cheaper/softer stainless blades. I then have some good 'headroom' beyond which the edge will gradually refine with regular stropping, and still cut very well for a good while. By the time I've reached a point that I feel the need to put the 'teeth' back into it with the sandpaper, the edge has approached a more near-mirror finish on the softer/cheaper stainless blade. On the other hand, good 1095 can go to and through mirror, and keep slicing like the devil all the way, with stropping on green compound & bare leather only.


David
 
I really agree with HH, on his opinion of draw cuts/push cuts, relating to edges. That seems to be well thought out, and articulated well.

David, I would love to see some bigger companies make some sprint runs or such, using some really good quality 1095. I think you could wind up with some killer blades. By bigger companies, I mean like BM and such. It would be pretty neat.
 
L2bravo said:
I really agree with HH, on his opinion of draw cuts/push cuts, relating to edges. That seems to be well thought out, and articulated well.

David, I would love to see some bigger companies make some sprint runs or such, using some really good quality 1095. I think you could wind up with some killer blades. By bigger companies, I mean like BM and such. It would be pretty neat.
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If only (sigh)... :thumbup:

If somebody managed to do 1095 like Schrade did on their older USA knives (they are my 'best example' for 1095), I'd think a whole new market could be resurrected around it. Maybe a 'niche' market for knife nuts like us, but still a winner, I'd think. :)


David
 
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In my experience, given the same steel and the same geometry, the polished edge will outlast the "toothy" edge by a wide margin.
 
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