03-25-2017, 07:19 PM
I tried the creepy 3 finger test (3-ft) years ago and then developed my own different way that works well for me. Nonetheless since this came up again here I decided I’d try again.
I just sharpened a blade with a A45 Trazact CP 337DC belt ~280 grit, then deburred on the rough side of a plain leather belt and a few swipes on my jeans. The blade got nice and sharp, 185g on the PT50. About right for a kitchen knife. It shaves hair and all of the other obligatory tests without problem.
I can put 3 fingers on that blade and press WAY harder that makes any sense to a normal man, and my fingers just slide. I’m sure I could press much harder, but common sense prevents me. Pressing very lightly is just not that informative. I just feels smooth.
Now, I know what it feels like to do that on a razor blade. It has a certain resistance. For super sharp blades I think I understand the 3-ft. But that “resistance” is just creepy. It has that "special" feeling because when your fingers are just bordering on epidermal leakage. To me the 3ft makes no sense with super sharp blades anyway.
It seems to me that a blade has to be sharpened to about 100g or less before the 3-ft test really works well. 100g is sharper than I need or want the blade for edge retention purposes.
Here's an image of the blade at ~200X. It takes a little practice to understand some of the microscope images. Shadows can make grooves look like a super jagged saw edge. It can be difficult to get the light just right. Just zoom in on the image and you can see what looks like a very rough edge is just shadows. Nonetheless, 280 grit does leave a nice "toothy" edge. I only post the image to show that this is not a highly polished edge.
So, even though I gave it another honest try, I still don’t get it. Anyway, it was an interesting experiment to try again, even though the whole idea of the 3-ft is against my better judgment.
I just sharpened a blade with a A45 Trazact CP 337DC belt ~280 grit, then deburred on the rough side of a plain leather belt and a few swipes on my jeans. The blade got nice and sharp, 185g on the PT50. About right for a kitchen knife. It shaves hair and all of the other obligatory tests without problem.
I can put 3 fingers on that blade and press WAY harder that makes any sense to a normal man, and my fingers just slide. I’m sure I could press much harder, but common sense prevents me. Pressing very lightly is just not that informative. I just feels smooth.
Now, I know what it feels like to do that on a razor blade. It has a certain resistance. For super sharp blades I think I understand the 3-ft. But that “resistance” is just creepy. It has that "special" feeling because when your fingers are just bordering on epidermal leakage. To me the 3ft makes no sense with super sharp blades anyway.
It seems to me that a blade has to be sharpened to about 100g or less before the 3-ft test really works well. 100g is sharper than I need or want the blade for edge retention purposes.
Here's an image of the blade at ~200X. It takes a little practice to understand some of the microscope images. Shadows can make grooves look like a super jagged saw edge. It can be difficult to get the light just right. Just zoom in on the image and you can see what looks like a very rough edge is just shadows. Nonetheless, 280 grit does leave a nice "toothy" edge. I only post the image to show that this is not a highly polished edge.
So, even though I gave it another honest try, I still don’t get it. Anyway, it was an interesting experiment to try again, even though the whole idea of the 3-ft is against my better judgment.