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 Post subject: The ULTRA fine grits?
PostPosted: Mon Sep 17, 2012 10:03 pm 

Joined: Wed May 02, 2012 11:14 am
Posts: 188
Location: Florida, USA, Earth
Brief history. I'm fifty something and have been sharpening my own pocket, hunting, etc. knives since Dad showed me how. I have always gotten my knives to where I could shave my arm and stopped there. Two Arkansas stones were all that was needed. In the past few years I've learned there was a lot farther you could go. I have gotten edges sharp enough to whittle a hair which I would have thought impossible 5 years ago. Now, when I look at stropping pastes I'm seeing .5 and .25 micron pastes and sprays. My question is how much difference is there when stopping after .25 micron than if I had stopped at 1 micron? Even (especially) when using better tools you have to have the skill or ability to get the results the tool is capable of. I have inexpensive diamond paste I got on ebay as coarse as 28 micron. Also, 14 and 5 micron. Then I have the 3 DMT pastes stopping as fine as 1 micron. I am getting polished, VERY sharp edges even when stopping at the 14 micron paste. I just ordered the EP strop with the Boron Carbide 1 micron paste. The reviews are compelling and if I like it as much as those folks do I'll get a bottle.

My ability has gotten better over the years. Every time I get an edge sharper than I have before I wonder when will the edges stop getting better. So, is there really much difference between 1 and .25 micron when used by someone skilled enough?

Jack


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 Post subject: Re: The ULTRA fine grits?
PostPosted: Mon Sep 17, 2012 11:41 pm 

Joined: Tue May 29, 2012 12:29 am
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The difference is big but more for bragging rights. @ .25 microns its actually difficult to feel the edge because by the time your fingers feel the edge cutting in the edge is deeper than you realize. It's pretty amazing and equally hard to produce. The level of polish is pretty crazy too, its so shiny its almost black and seems to disappear depending on the angle viewed.

My opinion, its fun to go down that road and gives you a good reference point to the level that sharpness can be taken to. A mirror polish can be a bit captivating too and almost hold onto your better judgement as to how the edge should be sharpened for its intended task.

Have fun and remember to test you edges with the finishes you have selected to better understand the pro's and con's of each finish.


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 Post subject: Re: The ULTRA fine grits?
PostPosted: Tue Sep 18, 2012 1:59 am 
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Posts: 473
If you are able to produce the results you are talking about, and see people doing even more, rest assured:

It is for fun.

It does nothing.


I have done a fair share of it myself, but again--it's for fun. Something is wrong with my brain--after years of sharpening untold amounts of steel, I still enjoy it. No idea why.



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 Post subject: Re: The ULTRA fine grits?
PostPosted: Tue Sep 18, 2012 10:06 am 

Joined: Wed May 02, 2012 11:14 am
Posts: 188
Location: Florida, USA, Earth
burkecutlery wrote:If you are able to produce the results you are talking about, and see people doing even more, rest assured:

It is for fun.

It does nothing.


I have done a fair share of it myself, but again--it's for fun. Something is wrong with my brain--after years of sharpening untold amounts of steel, I still enjoy it. No idea why.


Are you telling me this is just for my enjoyment/amusement and I still won't be able to get girls? :(

One of the biggest pleasures I get is when someone uses a knife I sharpened and then watching the look on their face when they cut something. My favorite is when they cut, then just stop and look at the knife. :)

I always valued a sharp knife but didn't realize what could be done while sitting on the couch. You are right though, it is fun.

Jack


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 Post subject: Re: The ULTRA fine grits?
PostPosted: Tue Sep 18, 2012 10:44 am 

Joined: Wed May 02, 2012 11:14 am
Posts: 188
Location: Florida, USA, Earth
Like everyone I have figured out what stones to use (that I own) to progress from coarse to the finest I have. Sometimes I can skip a grit. Now that I am wanting to get into the ultra-fine grit abrasives I'd appreciate advice on grit progression. The finest I've owned is 1 micron DMT paste. DMT was the first I used and was sold on diamond paste when I brought back to life a set of chisels I was going to demote to prybars and buy a new set because I just couldn't get them sharp enough. The cost of the DMT pastes was justified by the money I saved on a new set of chisels. And, I could sharpen them myself. There's always that. :) The next product I'm trying is the boron carbide 1 micron on balsa. If/when I get some finer grit paste or spray can I jump to .25 or should I get some .5 or .75 as well? At this level of obsession you can't cheat I don't believe.

The BC really gets high praise and the balsa will be new territory for me. Last night, being impatient I sanded an untreated 1"x2" piece of pine and put some 1 micron paste on it. I was very happy with it. It imporved the edge on an already sharp knife. DMT recommends using MDF, hard wood or even glass when using their paste for plane irons and chisels. Do you guys ever just use plain glass for knives?

Just to let you know, I'm not a chef. I'm not even a cook. :) I deal mostly with EDC pocket knives, a few fixed blades, and chisels and such occasionally. The edges you guys/gals in the culinery field seem to want are sharper than any pocket knife needs to be. They want to be that sharp thought. :) . That's what I'd like also even though I don't really need it. We have a set of kitchen knives in a wooden block that we have had forever. 25 years plus. I don't know what they are and I know the entire set was under $100. The steel is pretty hard though. I can tell when sharpening them. That's about all the experience I have with food prep knives.


Jack


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 Post subject: Re: The ULTRA fine grits?
PostPosted: Fri Sep 21, 2012 4:03 am 
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Well let's start out with a few larger points.

Edges should be task specific. Thus an extremely coarse or fine finish should be used to best meet the task requirements. The edge for a straight razor is usually going to be very refined. The edge on a meat cleaver isn't too critical.

Edge refinement is limited by the steel. So a cheap knife, a given steel type (and how the knifemaker treats it) all limit your results. Going to more acute angles or more refined finishes is a point of diminishing returns. Much past a 2k edge on a Henkels is truly bragging rights - for the first cut or two.

Now a high quality knife or tool or straight razor - you bet a finer edge helps. Again there is a task dependency and personal preferences.

It helps to think of pastes and stones on the same scale. Thus a 16k stone is a 1 micron paste. A 30k stone a 0.5 micron compound, etc etc.

And while we are talking of ultrafine grits, note that the 0.025 micron (625,000 grit) polycrystaline diamond spray is 10x fine than the quarter micron (64,000) grit.

So how much of a jump is a good idea between grits? Well this depends on how abrasion resistant a steel is AND not just the particle size but the TYPE of particle.


So obviously a 1 micron finish is 4 times coarser than a 1/4 micron finish. A 0.75 micron (24k) finish is 3x coarser than 1/4 micron - an easier jump.

Beyond 1/4 micron a eighth micron is a 2x jump. A tenth micron is 2.5x jump - both very 'doable', A jump from eighth to tenth micron is unnecessay. A jump to 0.025 is a 4x jump from tenth micron - also doable. Also CBN and (especially) poly diamond lend themselves to bigger jumps. And high quality compounds and stones that have a high concentration of abrasives also are significantly advantageous - especially with abrasion resistant steels. I'll ignore various belt grinder formulations for the moment as a separate topic.

It is VERY important to understand that just going to higher grits is not a panacea for all sharpening ills. This is especially so for freehanders, who sometimes get increasingly imprecise geometry going to finer grits, succeeding in rounding off the edge rather than refining it, giving a duller but more shiny edge, often confusing it with a runny edge. This is not an easy concept and I'm sure it will be a matter of debate. Thus a soft strop yields an imprecise geometry. Not that critical if it is your final grit level, but if you do a series of strops this 'slop' can really give you indeterminate results.

In the end you need to experiment and find your level of refinement angles, geometry etc - for each task - cutting veggies, meat, tree trunks and bones, etc etc. If you like to push cut (knives, straight razors, plane blades) more than slice (other knives), your edges should reflect this. If you are cutting on a soft endgrain board, bamboo or (EEK!) a glass or marble surface, your ideal edge should be different.

And there is the undeniable pleasure of being able to pull a knife out of your pocket and demonstrate a level of sharpness few have ever seen :) And on this point I'm not singling myself out, but rather a number of sharpeners on this board.

---
Ken



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 Post subject: Re: The ULTRA fine grits?
PostPosted: Fri Sep 21, 2012 10:28 am 

Joined: Wed May 02, 2012 11:14 am
Posts: 188
Location: Florida, USA, Earth
Ken,

Thanks for your detailed reply. A lot of it made sense to me based on past experience. Especially when going to finer grits and free-hand sharpening. All my life I used two Arkansas stones, med & fine and was getting very good results. Then I bought an ultra-fine stone thinking I was going to get the unbelievable sharpness I thought was possible only in movies. :) I ended up making my knives duller. :( In the past 5 years or so I've learned a lot about sharpening thanks to people like you and others. Now I'm getting results that are in the movies. :) Of course I want better just for fun as another poster said. :) I think I have enough good quality tools now to challenge my skill. I am expecting the EP balsa strop with boron carbide paste (1 micron). I'm going to try to not get any more products until I am getting consistant results with what I have. I have gotten a knife screaming sharp and thought "I have really improved". Only to find my results on the next knife not as refined. Consistancy (not luck) is the key. I'll wait on .25 micron spray or paste for a while. Once I am consistant with a strict regiment of stones and strops I'll be able to see an improvement with a finer grit I hope. Going to finer tools before my skill is ready will just be confusing, just like the ultra-fine stone I got years ago.

Thanks again.

Jack


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 Post subject: Re: The ULTRA fine grits?
PostPosted: Fri Sep 21, 2012 8:57 pm 
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That sounds quite reasonable. Perfecting your skills at lower grits (particularly consistency) is key.

A lot of my customers who have been using Ark. stones really enjoy using my 4.5 micron CBN either on a strop OR putting a drop of it right on your Ark. stone!

So 4.5 microns is ~ 4k grit - slightly finer than your Ark. stones. So this brings up another interesting point. Ark stones don't work particularly well on more abrasion resistant steels because they are not made of a material that is that hard - measured on a Mohs hardness scale. So they cut very slowly. CBN is quite hard and takes a Ark. stone (eg Black surgical or white translucent) up to a whole new level. The stone itself acts as a platen for the particles AND also slightly abrades the stone, making it more aggressive too. Send me a PM if you want to 'taste' some.

---
Ken



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