Photos Coarse edges!

maximus83 said:
Good point. I've been avoiding serrations for a long time, but there are times when you still want that degree of slicing aggression, but without having to deal with serrations.

Here's a quick subjective example of how this is useful. I took some 1/4" sisal rope, would hold it in a loop, and try to cut through it in a single strong draw cut with edge facing up. Used the above knife, an Ontario Rat in D2, and a Spyderco Domino in CTS-XHP. The latter 2 have nice, but more polished edges at much higher grits. I have no way to measure in foot-pounds how much force it took, but the cheapo S&W with the sawtooth edge :) was by far the easiest to make the cut. First couple tries, the Rat couldn't even do it, it slipped off the loop until I used more like a sawing motion. Bad! And dangerous. The Domino cut it without sawing, but with considerable torquing on it by me. But the S&W was just a clean straight draw cut and sliced right thru it on the first try.

y4mRSggoQIYu59jX2SDf0zCikKuEsxFGI8YmVAJmz_VSXuZYm2lT4Pg6OMEEEEqrU47M-Hhzq-OaJoejTHL8IEJEh5Po6mofWwqt1Yc38WnWZyCsY0z6RO2EaaeqDM2rCiexLIgUVmh5ZAVqah_0rBrmhBQT6kswi3eXRIFocbwYQvyACKqgmkx_WvWT49UHxGMRfmS1Qf4Yx8-lZ1zCgezxA
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In my experimenting with 3/8" manila it normally took half the pressure to complete a cut when drawing vs strict pressure cut at average finish levels - about 600-800 grit. I don't have the numbers in front of me. As the edge polish went up, the amount of force relative to the coarse edge, when used with a pressure cut, trended downward. The opposite true of draw cutting.

Any lengthwise movement is greatly assisted by lower grit values, pressure cutting is greatly assisted by higher. I always meant to do a detailed study of at least one or two steel types at similar geometry to see where they intersected - where the least penalty with either cut method lies. Anecdotally is probably in that 400-800 range, with considerable bias advantages going higher or lower.
 
^So that seems to accord with what I've been seeing. To paraphrase what I think you're saying:
  • Maybe 400-800 ANSI is a good solid 'general purpose' grit range for most EDU knives.
  • Lower grits (<400) are handy when you want strong slicing aggression on mostly draw-cut types of applications.
  • Higher grits (> 800) are handy when doing more pressure or push-cutting types of applications. Q: Is this why a lot of kitchen knife sharpening practice tends to go up into the much higher grits?
 
maximus83 said:
^So that seems to accord with what I've been seeing. To paraphrase what I think you're saying:
  • Maybe 400-800 ANSI is a good solid 'general purpose' grit range for most EDU knives.
  • Lower grits (<400) are handy when you want strong slicing aggression on mostly draw-cut types of applications.
  • Higher grits (> 800) are handy when doing more pressure or push-cutting types of applications. Q: Is this why a lot of kitchen knife sharpening practice tends to go up into the much higher grits?
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We should probably ask HeavyHanded HeavyHanded to specify what grit standard we're talking about. 400-800 grit could mean a lot of different things. In microns, ANSI would be 22-8.5 while FEPA F would be 17.3-6.5 and JIS would be 40-20.
 
Fog, my wife really likes a 320 grit India on her kitchen knives. Push cutting carrots or slicing tomatoes. DM
 
miso2 said:
Make sense.

One of the most polished (or rather smooth) edges with the edge radius around 5 nm (this one is used and probably not that "sharp" anymore).
It excels in push cutting but doesn't seems to have any slicing aggression and slips on skin.

Glass_knife.JPG
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Sorry, I posted it prematurely.
I guess what I wanted to say was something we all know already but wanted to make it clear for myself.


That glass knife, the most smooth (even) edge with a very small edge radius, does not have slicing aggression.
We also know that an edge of broken glass (or obsidian) slices and push-cuts (at least on some parts of the edge) very well with a similar edge radius.

Then, slicing aggression has to come from a serration (or some wavy structures).


So any knife edges with slicing aggression would have to have some sort of serrations.

If these are all true, then a coarse edge polished with a high grit without loosing the "tooth" would probably be like a broken glass edge and have a good balance of push cutting and slicing abilities.

A very polished spyder edge may be like this.
An edge finished at #60 or #120 may also behave like this when refined enough (like what FortyTwoBlades FortyTwoBlades said above).
Or one finished with even coarser stones like DMT XXC might be better if it can be refined?
 
FortyTwoBlades said:
We should probably ask HeavyHanded HeavyHanded to specify what grit standard we're talking about. 400-800 grit could mean a lot of different things. In microns, ANSI would be 22-8.5 while FEPA F would be 17.3-6.5 and JIS would be 40-20.
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ANSI, roughly 800-1200 JIS.

FortyTwoBlades said:
Anything on the coarser end works nicely. What I like doing with most of my knives is I set a coarse scratch pattern and then lightly hone using a fine stone just to get the apex really crisp without erasing the coarse pattern.
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I just reset one of my kitchen slicers on an 80 grit stone with a micro using an 8k stone. The edge gets thinner even though it is a less acute angle. It retains a lot of along edge variation and has a little better pressure character, though still is obviously a draw cutter for offhand food prep. This is a great strategy for EDU as well, depending on the task I just run the initial edge grind more or less coarse.

I'll try to get a decent pic.
 
HH, I will try add a micro too. On top of the 60-grit edge on that soft Chinese stainless, would it make sense to try a 2m to 3m abrasive (like the DMT EEF, or the Alox Ptarmigan @ 6K JIS) to create a +2 dps micro?

What advantage is the micro offering on the super coarse slicer?

Also, what is your thinking around this type of low grit for an EDU, vs the 400-800 range we were talking above? This is optimized for heaving slicing?

HeavyHanded said:
I just reset one of my kitchen slicers on an 80 grit stone with a micro using an 8k stone. The edge gets thinner even though it is a less acute angle. It retains a lot of along edge variation and has a little better pressure character, though still is obviously a draw cutter for offhand food prep. This is a great strategy for EDU as well, depending on the task I just run the initial edge grind more or less coarse.
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maximus83 said:
HH, I will try add a micro too. On top of the 60-grit edge on that soft Chinese stainless, would it make sense to try a 2m to 3m abrasive (like the DMT EEF, or the Alox Ptarmigan @ 6K JIS) to create a +2 dps micro?

What advantage is the micro offering on the super coarse slicer?

Also, what is your thinking around this type of low grit for an EDU, vs the 400-800 range we were talking above? This is optimized for heaving slicing?
Click to expand...


If it works for your EDU I'd give it a go. Most utility work does not involve a lot of pressure cutting, at least in my experience. This is an individual thing though.

As to advantage it improves the coarse edge ability to pressure cut and maybe even toughens up the edge a bit. This is a great way to customize the edge compared to finding that "just right" stone to get the desired finish.
 
maximus83 said:
"Not the best pic"? Geez, that looks great, and so does your edge. What process or tool are you using to put that edge on there?
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Thanks.
I used Congress Tools Moldmaster #240 and PSA 1 micron diamond suspension.
After reading posts on this thread, I feel that I should try #80 or #120.
 
I was traumitized this morning when I got to work and realized I had left my cooking knife at home!
Knowing the knives at work are complete crap as well as uncared for I had no idea how I would get thru the day.
Finally I picked one that was closest to my knife that I had forgotten and took a look at the edge. It was horrendous! Ace Hardware is on the same block as my work so went there and bought a few sheets of 80 and 120 grit.
About a dozen strokes on each side of the blade on the 80 grit and a test of sharpness on a Tomato .
Yeehaw! I can work with this.
Thanks to this thread I learned a coarse edge on even the cheapest of knives will get me through a day of work. Thanks BF!
 
FOG2 said:
I was traumitized this morning when I got to work and realized I had left my cooking knife at home!
Knowing the knives at work are complete crap as well as uncared for I had no idea how I would get thru the day.
Finally I picked one that was closest to my knife that I had forgotten and took a look at the edge. It was horrendous! Ace Hardware is on the same block as my work so went there and bought a few sheets of 80 and 120 grit.
About a dozen strokes on each side of the blade on the 80 grit and a test of sharpness on a Tomato .
Yeehaw! I can work with this.
Thanks to this thread I learned a coarse edge on even the cheapest of knives will get me through a day of work. Thanks BF!
Click to expand...
What were you able to use as a backing for the sandpaper?
 
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