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+--- Thread: Tooth vs Polished #2 (/showthread.php?tid=23)
Tooth vs Polished #2 - grepper - 03-16-2017
Jim,
I had originally posted this in the other thread, but as so often happens in forums the thread morphed off into another interesting subject. I think that's just fine, but I would like to revisit the issue because I want to get a better understanding of it.
The original question was:
I had learned, and intuitively it makes sense to me that a polished edge would have better edge retention than a toothy edge. Fairly recently I was wandering around the ‘Net and saw some stuff saying that due to the way a toothy edge wears, that a toothy edge could have better edge retention than a polished edge.
At this point I have no idea where I saw that info, but it ran contrary to my understanding. I have always thought that a toothy edge was less stable because the peaks of the “teeth” were not well laterally supported.
You replied that a toothy edge is has better overall retention.
Can you help me to understand why? Would that only be true with non-impact use? For example, what about if you were chopping carrots on a cutting board. Would that type of impact make a difference?
RE: Tooth vs Polished #2 - Ankerson - 03-16-2017
Basically there is very little or no real aggression with a polished edge so the smoother edge dulls quicker when cutting the same media.
There are however many factors involved here, but in my testing coarse edges hold an edge for a very large percentage over polished. I have personally seen over 400% differences using the SAME knives, but with different edge finishes.
There are a lot of variables here to contend with and all matter: Steel, Rockwell hardness, Blade and Edge Geometry, Edge Finish, Media being cut, etc.
Now we are talking about knives and cutting things here vs some sort of AX or similar related tools.
Now talking about the general/typical kitchen knives that people generally buy none of them will hold an edge very well or for very long so the differences will be smaller than the knives with the higher grade high alloy steels.
RE: Tooth vs Polished #2 - grepper - 03-16-2017
400%! Wow. That's really significant. BTW, I love that. I like a toothy edge, but I always thought it was at the expense of edge retention.
Umm, what grit? Where's the sweet spot for a general purpose/kitchen knife?
Could you please explain a bit more what your mean by, "Basically there is very little or no real aggression with a polished edge so the smoother edge dulls quicker when cutting the same media."?
Why would a more aggressive edge dull less quickly than a smooth edge? It seems counter intuitive. I would think the little "teeth" would tend to bend and wear more quickly because they are not well laterally supported. That's why I've always thought that a smooth edge had better retention.
RE: Tooth vs Polished #2 - Ankerson - 03-16-2017
(03-16-2017, 05:44 PM)grepper Wrote: 400%! Wow. That's really significant. BTW, I love that. I like a toothy edge, but I always thought it was at the expense of edge retention.
Umm, what grit? Where's the sweet spot for a general purpose/kitchen knife?
Could you please explain a bit more what your mean by, "Basically there is very little or no real aggression with a polished edge so the smoother edge dulls quicker when cutting the same media."?
Why would a more aggressive edge dull less quickly than a smooth edge? It seems counter intuitive. I would think the little "teeth" would tend to bend and wear more quickly because they are not well laterally supported. That's why I've always thought that a smooth edge had better retention.
It all comes down to pressure and the basic act of cutting/slicing.
Once the edge loses it's aggression it's done, it has no bite.
For kitchen knives I would say something in the 320 to 600 grit range depending on needs with 400 grit being the sweet spot I believe.
RE: Tooth vs Polished #2 - grepper - 03-16-2017
I guess that makes sense. If an edge has no bite or friction, obviously it's not going to cut.
Are you equating edge retention with usefulness or sharpness?
For instance, I can understand how a dull serrated knife would be much more "useful" cutting something like rope or cardboard than even a slightly dull smooth edge, even thought the smooth edge may test with the KN100 as being sharper.
From a sharpness testing point of view, are you also saying that the toothy edge would also maintain sharpness better?
I guess I'm trying to get clear in my mind the correlation between edge retention and sharpness. Or maybe just exactly a clear definition of what the term "edge retention" means from a testing point of view.
Does that make sense? Some things make me feel really thick headed!
RE: Tooth vs Polished #2 - Ankerson - 03-16-2017
(03-16-2017, 06:15 PM)grepper Wrote: I guess that makes sense. If an edge has no bite or friction, obviously it's not going to cut.
Are you equating edge retention with usefulness or sharpness?
For instance, I can understand how a dull serrated knife would be much more "useful" cutting something like rope or cardboard than even a slightly dull smooth edge, even thought the smooth edge may test with the KN100 as being sharper.
From a sharpness testing point of view, are you also saying that the toothy edge would also maintain sharpness better?
I guess I'm trying to get clear in my mind the correlation between edge retention and sharpness. Or maybe just exactly a clear definition of what the term "edge retention" means from a testing point of view.
Does that make sense? Some things make me feel really thick headed!
Actually there really isn't a difference in sharpness level that can be had between coarse and polished edges.
It all comes down to sharpening ability.
I have gotten both down to the single digits on the KN100 so it is completely possible. That when I was trying to see just have far I could take the edges. I don't bother with it all that much anymore, I normally get my edges in the 50-60 range and call that good.
There are a lot of misconceptions or as I call them urban legends about sharpening, steels, etc that are fueled by those who want YOUR MONEY.
RE: Tooth vs Polished #2 - Mark Reich - 03-19-2017
I've been reading this thread with interest, since it's one of the most common questions. These are JMHOs.
It's not just the size of the "tooth" it's also how "pointy" the teeth are. I can assure you though, 400 grit will out cut 4000 grit. Nothing doesn't cut like a smooth edge.
To have pointy teeth, you must have a cleanly apexed edge and the right sort of abrasive. It's easy to get pointy teeth with a diamond stone or diamond compound, and it's virtually impossible to get tooth from an Arkansas oil stone, or AlOx (green) compound.
The best way to determine what sort of edge you have is the three finger test, but comprehension of it seems low. For whatever reason, it seems most people might not know what it's supposed to feel like. I mean, here we are discussing it yet again.
The key to the three finger test is the angle of the knife in relation to the surface of your skin. If the knife is at a very shallow angle to your fingertips, you can't begin to cut into nerves. You only need to slide your fingers down the edge about 1/8". I think it's best to use both hands, like I always see if a blade shaves on both arms. Normally sorts out wire edges.
As you stop your tiny slicing action, pull the blade away from your skin at a 90* angle. If the edge bit into your fingerprints you will feel the edge pop out of the tiny slice. Otherwise, you repeat this once or twice per second, gradually adding pressure until you determine what the edge feels like.
You can easily do this while talking and looking someone right in the eye. He'll never even see you totally read the edge. This is especially valuable for event sharpening where you want to have interaction with the customer without wasting any time. You can't see "sharp" anyway.
One time I handed my knife to a friend who needed to cut a piece of rope. He started "sawing" on the rope, and to my chagrin, it didn't cut at all! Knowing the edge was shaving sharp, I had to show the difference between push cutting and slicing, but that incidence was a huge lesson.
Tooth is generally much more productive than a polished edge. For this reason, my everyday hone has become 16 micron (1000 grit) poly diamond compound.
YMMV JMHO
RE: Tooth vs Polished #2 - grepper - 03-20-2017
OMG! I had to look up YMMV
.Over the years I've learned to feel edge sharpness by, with a very light touch, pulling my finger at a shallow angle to the blade down off the edge. I just did it with a blade that measures 140g BESS. Then I looked at my finger. Sure enough there were micro incisions on my epidermal layer! Doing that test the blade has sort of a sticky, resistance. Hard to explain, but once you feel it, it is easy to identify again.
I can tell instantly if a blade is very sharp or not. I'll call it the one finger test! It seems really easy, but then I've been doing it for years with a lot of blades. I guess anything you do for years seems easy.
Personally, the three finger test gives me the willies because it involves sliding along the length of the blade. If the blade does not provide that "special feeling", the tendency is to press harder and see if that makes a difference. Yikes! But, that's just me. IMHO. YMMV. What works for me my not be the best for someone else, and visa versa.
What would be really cool would be an instant auto-threader for the PT50!
So, Mark, for sharpening an "everyday" knife, like a kitchen knife, what have your found produces the best results? Sharpen to 400 grit and then hone @ 1000? Do you think 400 grit gives enough tooth?
RE: Tooth vs Polished #2 - Mark Reich - 03-22-2017
Sorry Grepper. Should have remembered this thread.
I don't mean to complicate things, but diamond plates are different than water stones of similar grit designations. IMHO, the 400 grit diamond hones have so much tooth that it's hard to get a clean edge. Great for profiling though.
I really don't mind 400-500 grit water stones. Especially for softer German type kitchen knives.
Most of the time I use 1000 grit Shapton for EDC, maintain with 16 micron poly diamond on leather.
I like a 2K water stone on my Japanese kitchen knives, and maintain with 8 micron poly diamond on leather.