What is “Sharp”

[John Haley]

It seems that the more knives I sharpen with my WE, the more confused I become about, what, exactly, is sharp? I can spend two hours or more running through the diamonds and then the entire Chosera range, followed by stropping and have a very polished edge under the loupe… BUT… it doesn’t seem any sharper, and sometimes not even as sharp as stopping after the 1K diamond and maybe giving a quick 1µ strop. Again, yesterday, I got fantastic results on a CMP154 knife with the abbreviated process.

[Leo James Mitchell]

Check, check and double check that you have raised a burr right out to the edge of the blade and the complete length.
Except when raising the burr, do not use too much pressure…for all the rest caress the blade with you paddles.
Remember your diamonds need a break-in period.
Be sure you are giving equal strokes on both sides.

My two cents worth! 😉

Leo

[Leo Barr]

Scandi grind

Convex taper and bevel
In practice I believe it is the geometry it is what lies directly above the bevel and the transition between one and another that makes for a sharp knife.
This is why perhaps multiple bevels or a good convex bevel will produce a blade that cuts deep.
I find that if I pinch a blade at the point where taper meets bevel and can feel a transition the blade is too fat and the cutting bevel may be too wide or to steep in the exception of a Scandi grind.
This is why I think ceramic knives are poor because the material is too brittle to take a good taper and therefore they are fine for cutting processed foods or something like lettuce but not a lot else.
The taper to the bevel should be virtually to the edge and the bevel itself should be that small that it should be 0.5-1.0mm wide and then it really makes no odds if that bevel is a V or convex.

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[Craig]

Yea I’m getting pretty confused myself these days!!! I feel like after hitting the super fine ceramics that’s it. I understand the purpose of stropping, I think. I lower my angle by 2 and I feel like the mirror edge is not worth losing what I think is sharp!! But I’m still pretty new at the. Probably less the 35 knives in. I have been all over the forum trying to figure out if I’m doing something wrong. Even ask questions. By the way thanks to all that has answered!!! Pressure maybe?? But from what I have read trail and error. Don’t get me wrong I get things sharp!! Just have to find my winning combo!!! Get topic by the way !! I feel the same!! Good luck and sharpen on!!!!

[Leo Barr]

Get some knives that do not matter – cheap and experiment I think it is easy to expect a mirror bevel to be the answer but often the really important part is the shape – geometry even if the steel is inferior you can taper it well and then put say a 20Ëš + bevel on it to allow for the soft steel and get a good result . But put an edge say at 15Ëšon to a thick blade the bevel will be very wide and the shoulders of the bevel will be like a limiter on the performance the shoulders will get stuck on what you are cutting try slicing through a piece of paper held up and you will see that a nicely thinned blade will pass through the paper as if it is not there even if the edge has not been refined that much ; then try to slice paper with a thick blade whose edge has been through all you stones and strops and it will be hampered by its thickness on the top of the bevel which is why multiple bevels or convex bevels are the answer to allow a knife to cut well especially gutting your fish.

[Leo Barr]

Leo Mitch offers the other good advice are you getting to the edge if in doubt use that starting stone a little longer I think it is normal when beginning to not sharpen through to the edge I reckon I did that on at least the first dozen knives I did on an Edge Pro the best advice is to use a lube as well and possible a marker pen so you can see clearly if you have reached the edge .
Another worthwhile bit of advice Leo Mitch mentions is not too much pressure it is the same using sand paper on wood or paint press too hard and the paper does not last , it clogs up easily and the surface becomes uneven since the pressure varies its the same say with an orbital sander or palm sander let the grit and movement do the work if you do not press too hard it is easy to keep a uniform pressure over the span of the blade.

Leo Nav

[Eamon Mc Gowan]

Anther point to make and it fooled me a lot when I was first putting edges on with the We. When you go further up the grits the less tooth you have? When I got done with the 1K diamonds and felt the edge it felt very sharp? Then I bought the Chosera’s worked my way up to 10K and it did not “feel” as sharp?
Providing you are getting to the edge of the edges? The difference in sharp is amazing? The 10K chosera you can shave with, but try to cut rope and surely it will fold on you. A 800 diamond will cut the hell out of rope, but will bring a tear to you eye if you try to shave with it?
Somewhere in between all this is the edge the specific task needs? But as stated before all is for nothing if the edge of the edge has not been hit? I highly recommend the black sharpie and a loupe to check all edges after each stone till your sure. I don’t use a sharpie every time these days, but I always check with the loupe! Many a time I have been fooled and especially with the chosera’s!! When working with the chosera’s make sure to use your angle cube on every stone!!! The slightest deviation with chosera’s will just ruin a perfectly good edge!
Good luck and have fun!

[Leo James Mitchell]

Thanks for those points Eamon and I think you have answered the question most clearly. In a sense there are different sharps depending on what you are cutting.An edge that whittles a hair may fold and die if you put it to work cutting a hemp rope or chopping carrots. It was a question I asked a bunch of the finest sharpeners in the world on another forum and they missed this point. Polishing molecules will not get you and edge you want to take out on a camping trip or in a possible survival situation.
Great points my Irish friend!

Leo

[Eamon Mc Gowan]

Thanks for those points Eamon and I think you have answered the question most clearly. In a sense there are different sharps depending on what you are cutting.An edge that whittles a hair may fold and die if you put it to work cutting a hemp rope or chopping carrots. It was a question I asked a bunch of the finest sharpeners in the world on another forum and they missed this point. Polishing molecules will not get you and edge you want to take out on a camping trip or in a possible survival situation.
Great points my Irish friend!

Leo

Leo,
You are far to kind to me!
Thank you,
Eamon

[John Haley]

Thanks for the replies. It still confuses me a bit as I sharpen away. Since the whole process is fairly new to me, I’m probably getting better at it without realizing it. I do believe that many of my early sharpening processes were hurried, i.e., not done sufficiently or correctly which may be showing more now that I have some experience, albeit minor, with the WE.

[tcmeyer]

Last year, I watched a dermatologist slice a very thin sample of skin off a growth on my forehead and was amazed at the fact he didn’t have to work at the slice to get the cut started. So what was different about scalpels? The sharpest knife I ever sharpened couldn’t do that.

As I’ve mentioned in another thread, I’ve been studying sharp stuff, including scalpels and razor blades and have found some interesting stuff.

Most notable, and most applicable here is a box of scalpel blades I bought on Amazon. Who knew they were so cheap? 100 sterile, foil-packed blades for $13.50. A stainless scalpel handle cost $3.00. Shipped. I had cut and micro-photoed another type of scalpel but these were interesting. They had normal grind marks on both sides, but on one side, and only one side, it had been stropped. I haven’t measured the grind marks yet, but they look to be 600 to 800 grit. Sort of a hybrid “toothy” edge, which, by the way, makes for a very nice precision slicing device. I was able to cleanly remove a patch of raised skin (commonly found on the hides of male humans approaching 70 years of age) from the back of my hand, with no need to work at establishing a slice line. It bit into the skin at the first application of light pressure. None of my sharpest knives would do that. Their polished edges would slide right over the skin, but then scalpels do have a more acute included bevel angle.

When I get a chance in the next couple of days, I’ll post a few photos here.

I’m as fixated as any of the denizens of this forum on the achievement of a perfect edge, but have begun to become convinced that “working” sharp and mirror sharp are mutually exclusive goals.

[Leo James Mitchell]

Very interesting experimentation and observations. Well done!

Leo

[Leo Barr]

We have been doing a lot of cutting tests lately and the polished edge has won every contest. We just did a test on towing straps and, I and the customer, both felt a edge with a little bite would work better but we were wrong. The polished edge went through the strap much easier. I think you will fin the same thing with the rigging knife. However the secret to any job, especially this one is a thin blade. Rigging knives have fairly thin blades but they are not usually real high quality. The next thing you want is a very narrow bevel. I just received a new knife and the bevel was much wider than I like. It was sharpened at 19 degrees and even with a polished edge it would not slide through a piece of cardboard. So I went down to 12 degrees and cut in a second bevel. I cut my primary bevel down to 20 thousandths, I think this is the absolute minimum, then I polished the bevel., without touching my 19 degree edge. Now the knife will slide through a piece of cardboard effortlessly. Often when trying to do difficult cutting jobs, people focus to much on the edge and not the shape of the blade, which is just as vital. If I was looking for the best knife for cutting this rope I would try a 4 or 5 ” Japanese laminated cooking knife. These blades are stainless on the outside and have a thin layer of very had carbon steel down the middle.

This is a quote from Ben Dale of Edge Pro.

The sharpest edge I have which is untouched is that of my Rockstead Un I photographed it on a duvet and I found the blade whilst resting on the duvet had cut through both the cover and into the duvet just by been placed there I only noticed it after I had finished photographing . The Edge on the Un is finished on 2K/3K grit wet & dry sandpaper from the factory so it is slightly toothy the angles are 12Ëš at the kissaki and 15Ëšto the heel the steel is ZDP 189 so perhaps the level of polish is relative to the quality of the steel that is if the steel is strong enough to take the edge if it is not the edge may roll ; so perhaps a lower quality steel is more suited to less refinement since say a blade of lower quality steel finished with 600 grit may well chip in use rather than roll if it is more refined.

I have to say we have opened up a tin of worms perhaps other would like to add to this topic.

The edge (slightly out of focus 400X) of the Rockstead Un

Leo Nav

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[Leo James Mitchell]

One has to be careful when talking about sharpness not to stray over into talking about the suitability of an edge to a certain task as I have just done.
The edge Leo Nav has just described is indeed sharp. So sharp is sharp as we see with Leo’s example. There is no doubt there. I guess where I keep on erring is slipping over into talking about suitability of an edge to a task…when one does that we are then talking about edge geometry i.e. is an edge of 12 dps and an edge of 20 degrees dps that are of equal keenness suitable to make fuzz sticks and baton wood into kindling over time.
My mistake in thinking, and I suppose this is where the can of worms comes into things,is talking about durability not sharpness precisely.
Hmmm! Is that clear as mud Leo Nav or anybody. My old noodle is spinning its wheels here.

plain Leo

[Josh]

Excellent points Eamon. People have to realize that there are two different types of cutting – push cutting and slice cutting. The former is done with a highly polished edge and the latter with a low grit edge. It all depends on what you want to use your blade for. I have found over the years that for almost all tasks the toothy low grit edge works much better for EDC tasks whereas the polished edge has a very specific limited use (i.e. Straight razor). As my diamond stones have worn in more and more, I have found myself decreasing the grit I finish with on my EDC knives – it started with 1k then went to 800, now I’m down to a 600 grit finish and am loving it! I have not noticed any edge deterioration in toothy vs polished as Leo has. To confirm this, This process/testing would need to be done in a double blind test with the same knife with two different finishes on several runs. 🙂

You may be right Leo, but I’m just saying to confirm we would need to do this.

Josh

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