Recommendation? Aids for achieving "razor sharp" edges

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Karl H

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Apr 24, 2020
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I recently got a KME sharpening system. I have been able to achieve "scrape shaping" sharp edges that will occasionally, but not consistently, push cut printer paper.

I am looking for some aids to help me get the apex of my edges to be smoother and finer. My current targets are to be able to cleanly shave (without ripping) hair and gravity cut notebook paper. Based on this sharpness chart, I would estimate that my edge apex widths are currently about 0.3 microns wide and I want to get down to a smooth and consistent 0.1 micron width.

I am currently finishing on the KME Gold Series Extra Fine Hone - 1500 Grit and a leather strop with 1 micron Wicked Edge diamond paste.

I am looking for aids to help me get finer edges. In particular, I am looking for recommended visual aids and finer abrasives. Please let me know if there are any loupes or microscopes that you can recommend. I would also appreciate any recommended CBN or diamond abrasives finer than KME Gold Series 1500 grit.

Thanks for your time.
 
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I would guess one of two things:

1. You are not raising a full length burr on both sides. Which would mean that your apex (edge) is not complete and is "dull" in some spots.

2. You have raised a burr on both sides, but have left behind burr on some parts of the blade. Folded over burr appears SUPER dull because it's like a little metal blanket laying on top of the edge. You'll normally detect this with paper as the cut going well until you hit a certain part of the blade. Or, the cut goes well the first 5, 6, 7 times, but on the 8th (or 10th) time, it suddenly hangs or catches the paper. This later behavior is what happens with a burr was standing straight up, seeming VERY sharp. But then a little bit of cutting pushed the burr over and it collapsed.

I also guess that your edges are not in the 0.3 micron range, which would be 150 to 200 BESS. Just for fun, here's a little video I made about cutting paper with a knife. The knife in question scores ~125 BESS.


Brian.
 
As long as you understand that sharpening a knife to that level is entirely a novelty.....

1. Buy an exceptionally keen razor blade that provides a reference - Feather-Artist-Club-Professional-Super is my recommendation.
2. Use a simple steel knife, ideally just plain hard carbon steel.
3. You will need to sharpen your knife in the vicinity of 8-10 degrees per side.
4. Learn to strop freehand and follow these instructions.
https://scienceofsharp.com/2016/04/14/simple-straight-razor-honing/
 
bgentry said:
I would guess one of two things:

1. You are not raising a full length burr on both sides. Which would mean that your apex (edge) is not complete and is "dull" in some spots.

2. You have raised a burr on both sides, but have left behind burr on some parts of the blade. Folded over burr appears SUPER dull because it's like a little metal blanket laying on top of the edge. You'll normally detect this with paper as the cut going well until you hit a certain part of the blade. Or, the cut goes well the first 5, 6, 7 times, but on the 8th (or 10th) time, it suddenly hangs or catches the paper. This later behavior is what happens with a burr was standing straight up, seeming VERY sharp. But then a little bit of cutting pushed the burr over and it collapsed.

I also guess that your edges are not in the 0.3 micron range, which would be 150 to 200 BESS. Just for fun, here's a little video I made about cutting paper with a knife. The knife in question scores ~125 BESS.
Brian.
Click to expand...

I feel relatively confident that I am raising a full-length burr on both sides (by feel, with fingertip). I am raising the burr on a 300 grit stone. While my deburring almost certainly could be better, I don't think I have a folded burr either. The edge feels rough to the touch, but it doesn't hang up on paper or feel dull, at any point. It is entirely possible that I am not removing all of the deeper 600 grit scratches, when using the 1500 grit stone. I would ideally like to be able to visually confirm all of this with either a loupe or microscope.
 
Buying finer abrasives isn’t going to help you at this point as your troubles are technique based. You’ll likely end up with a lighter wallet and a heavier heart. Your current abrasives would get you easily push cutting newspaper and shaving arm hair with absolute ease. My vote goes in the ‘not properly removing the burr’ camp.
When done correctly the apex on both sides should be feel absolutely smooth to the touch.

a Loupe could help as well as spending a little bit more time on burr removal on both the stones and the strop. Good luck, it can be a frustrating road on occasion but as they say - practise makes perfect. You’ll get there
 
In no particular order:

* Any 10x (ish) loupe from Amazon or similar will let you see some good detail on your knife blades, including burr remnants.
* "pocket microscopes" are way higher magnification but may or more not be useful to you. I'd start with the 10x.
* I find a bright light shining behind the spine of the blade, directed at an angle downward shows me a burr quite clearly on most blades.
* You might try some different deburring techniques. The double angle technique (or just a microbevel) works quite well.
* A 300 to 600 grit edge should cleanly cut thin paper like news paper, ads, or phonebook. 300 should shave, but hang a little. 600 should mow hair off your arm (or leg) with little effort and a little drag.

The BESS tester is a bit expensive compared to one or two stones. More like the price of 3 good stones. But I think it's a great tool to have if you're a sharpening nut like I am. If you're not quite as crazy as me (or let's just say enthusiastic) then it might not be worth the investment for you.

Finally, you might peruse my Seven Secrets Of Sharpening sticky; you might find something there that helps you out a bit.

Good luck.

Brian.
 
With my KME and the standard diamond stone offerings and strops in 4um and 1um I can get most all my knives cleanly shaving arm hair and with-grain cutting receipt paper. Geometry starts affecting leg hair shaving a lot more and face shaving is well, no...
 
With your current setup you should be able to whittle hair.

Light pressure is key along with inspection of the edge when you get to this level of refinement.

You may be very well getting a great edge but may be over doing it and taking steps backwards with to much grinding.

Patience and practice is key to consistently getting a nice edge.
 
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