Super polished edges

Cliff Stamp said:
That's impressive, I have not seen it to date. I don't use high polishes much but will be seeing how far I can go with some push cutting edge retention work shortly.

-Cliff
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Whops. It actually isn't as impressive now. It had been a really well aligned wire edge. Stropping at the same final edge bevel must have brought up a wire edge that was very small, because as soon as I tried to use the knife on cardboard, the edge rolled.

Need to change my final stropping step.

So now my best edge will push cut photocopy paper at 90 degrees a few inches from the hand, but won't do toilet paper. Working on getting that better.
 
the_mac said:
... as I tried to use the knife on cardboard, the edge rolled.
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Visibly?

me2 said:
My final step is stropping on leather loaded w/ white buffing compound on a 1x30 belt sander.
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How long do you strop?

This loaded leather stropped edge seems to be superior to the white fine rod edge from the sharpmaker, in terms of edge holding.
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I would assume a deformation issue, I would be curious to see a 600 DMT rod vs stone comparison for such a reason. Of course you would want multiple of each to rule out just variances in grit. Have you tried the UF Sharpmaker rod?

Edge retention is highly linked to sharpness, opposite to how often promoted. Both increase at the same time, the truely exceptionally sharp edges are also extreme at edge holding as they are almost completely free of deformation/fracture/debris.

-Cliff
 
"How long do you strop?"

Typically there is a detectable burr from the previous 320 grit belt. This is sometimes the flacid, feathery edge described in the sharpening section of David Boye's book "Step by Step Knifemaking" (highly recommended btw). Lately I've developed a light enough touch to get a burr that is not visible by eye, but detectable by "stropping" the blade down my arm and feeling the burr pull the hair. I then strop long enough to remove any feeling or sight of this burr. Under a pocket microscope (one of your hints) the edge is quite clean and no reflection can be seen at 60x. This usually takes between 10-16 total passes across the belt, alternating sides every 1 or 2 passes.

I have not used the Sharpmaker UF stones. I understand they produce a significant increase over the fine white stones in push cutting ability, and from my experience that is saying something. Anyone know the grit of "stainless" white buffing compound? I started using it after reading Boye's book, and before I heard of CrO compound. I would like to try the 1, 0.5, or 0.25 micron diamond compounds, but cant justify it until I run out of the 6x1x1 bar of stainless buffing compound.

"Edge retention is highly linked to sharpness, opposite to how often promoted. Both increase at the same time, the truely exceptionally sharp edges are also extreme at edge holding as they are almost completely free of deformation/fracture/debris."

This may explain why the Vapor had such high edge retention relative to a Kershaw Random Task in S60V (AKA CPM 440V) that was sharpened on the flats of the Sharpmaker brown medium "rods" (triangles actually, for those who havent used one). I dont think it would have beaten the Random Task, but it was headed that way with no sign of slowing down. I just ran out of cardboard, and got tired.

How do you relate the above statement to the results of the BK7 at 100 grit A/O. I am still trying to work out my course grit sharpening, but stalled after my move. I'm still working on a hair shaving edge from the 800 grit waterstone or from a 120 grit A/O belt, stretched and used in hand, not in the sander.
 
me2 said:
I would like to try the 1, 0.5, or 0.25 micron diamond compounds, but cant justify it until I run out of the 6x1x1 bar of stainless buffing compound.
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If you contact DMT they are likely to send you samples for evaluation.

This may explain why the Vapor had such high edge retention relative to a Kershaw Random Task in S60V (AKA CPM 440V) that was sharpened on the flats of the Sharpmaker brown medium "rods" (triangles actually, for those who havent used one). I dont think it would have beaten the Random Task, but it was headed that way with no sign of slowing down. I just ran out of cardboard, and got tired.
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Angle, grit finish and edge quality (lack of deformation/fracture/debris) are extremely critical to cutting ability and edge retention. Considering responce of steels to those influences I think it would be more productive if in general people spent more time refining sharpening methods than looking to "upgrade" steels. If you take even a AUS-4 blade and truely optomize it for a given task it will blow right buy stock S30V blades from all but the most extreme of makers like Wilson.

Unless the edges are readily push cutting newsprint inch+ from the holding point you are only seeing a small fraction of the ability of the steel anyway and most knife profiles have far too much steel for what the knives need. I would rather have a Calypso Jr. in AUS-4A vs a Fulcrum in ZDP-189 for any cutting work. It isn't even a comparable choice. It is like asking - you have to dig a hole, do you want a shovel with a slightly rough handle and less than ideal head, or a really high end paint brush.

It has been awhile since I sharpened knives on 80/100 grit belts, but when I did I compared both manual and on the sander to see if the speed of the sander was being an influence it wasn't. I didn't have a problem obtaining very high sharpness edges with no burrs, my main problem was actually making the edges meet because I was usually working on extremely wide grinds and adjusting down from a obtuse bevel. When the edges get super thin they also overheat rapidly so you have to go extremely light. R.J. Martin has noted that better belts have an effect here which would make sense considering trying to use inexpensive benchstones on similar steels.

I recently did some work with the same 90 grit stone I used to sharpen the CRK&T blades and tried it on some S30V and ZDP-189. It was next to useless, it felt very slick and would not cut the steels well. Those AUS steels on the other hand are very low carbide, especially 4A and thus all you are cutting is just pure martensite which is likely why they obtain a high sharpness so easily (assuming you can remove the burr) even on such cheap stones. I also need to lapp it again because it doesn't break down in use so the surface gets slick.

-Cliff
 
I sharpen up to 8000 grit and and strop on leather followed by razor strop fungus(used for razors ).Somtimes i just sharpen up to 4000 grit which is sharp enough if im honest with myself.I did see a 30,000 grit stone somwhere, too expensive for me but i would like to see how sharp it made a knife. By the way Anyone know what grit the spyderco sharpmakers fine rods are?
 
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