Are some steels naturally toothy? 3 finger test gone wrong!

M

MichaelMyers

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Dec 10, 2015
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As some of you know I sharpen my knives and I like to use the 3 finger test to further evaluate the edge beyond slicing paper. That's how I know the edge is sharp vs really sharp I can do it safely in every case but this morning it went wrong. I sharpened my XHP steel CS Talwar with my regular 600 grit stone that I used with my other knives. It was sailing through paper whisper quiet so I test with fingers. With less than an inch slide along the edge I feel it bite into my index finger so i stopped. But it was too late blood was leaking out. Ouch! I test the edge on soft facial tissue and sure enough it sliced it clean. Never had a knife sliced so aggressively coming off this stone sure they all cut paper fine but wont do much to my skin or soft tissue. So my question is do some steels react differently to a the same sharpening stone? This XHP steel seem to take a very fine yet toothy edge. My finger hurts just thinking about it.
 
Don't ACTUALLY do it !?!

I have always felt XHP to be a fairly fine grained steel, closer to 1095 than to S110V

That said when ever I hear the words three finger test I cringe then laugh. I just plain don't get it and I must say I expect everyone who tries it to slice their fingers just as you did. I mean DUUUUUHHHHH.

Gee . . . I wonder if this blade is sharp . . . I will slice my finger with it and see . . .

I know the king of blade making shows it in his videos . . . but . . . I just assume that his teacher showed him to do this as a joke . . . you know while the other old masters watched and it shocked them all when he took them seriously and did it. They just assumed the kid's common sense and primal sense of self preservation would kick in but . . . noooooooo. Luckily his knife wasn't sharp at the time or some shhhhtuff.

I don't know how people survive it. I for one have better methods.

I'm just curious . . . do you plan to keep using this "test" ?

Here is a better method. Tells me waaaaaaaaaaay more about the sharpness and geometry (biased / rolled to one side or the other; enough clearance behind the edge or not; sharp here but not there; chipped and how bad . . . etc., etc., etc.,) of an edge :



 
MichaelMyers said:
As some of you know I sharpen my knives and I like to use the 3 finger test to further evaluate the edge beyond slicing paper. That's how I know the edge is sharp vs really sharp I can do it safely in every case but this morning it went wrong. I sharpened my XHP steel CS Talwar with my regular 600 grit stone that I used with my other knives. It was sailing through paper whisper quiet so I test with fingers. With less than an inch slide along the edge I feel it bite into my index finger so i stopped. But it was too late blood was leaking out. Ouch! I test the edge on soft facial tissue and sure enough it sliced it clean. Never had a knife sliced so aggressively coming off this stone sure they all cut paper fine but wont do much to my skin or soft tissue. So my question is do some steels react differently to a the same sharpening stone? This XHP steel seem to take a very fine yet toothy edge. My finger hurts just thinking about it.
Click to expand...
Hi,
do they push cut paper ? printer paper? newspaper?

600 grit is that P600/26micron or CAMI 600/16 micron ? (
856708-The-Grand-Unified-Grit-Chart )


It kinda sounds like you're getting good at deburring :)
 
In my limited experience, I found that burr removal is easier on XHP than high vanadium carbide steels like S35VN. XHP also takes a very aggressive edge.
I don't think I can move a well-sharpened XHP blade even 0.2" over my fingers without getting blood.

Miso
 
Wowbagger said:
Don't ACTUALLY do it !?!

I have always felt XHP to be a fairly fine grained steel, closer to 1095 than to S110V

That said when ever I hear the words three finger test I cringe then laugh. I just plain don't get it and I must say I expect everyone who tries it to slice their fingers just as you did. I mean DUUUUUHHHHH.

Gee . . . I wonder if this blade is sharp . . . I will slice my finger with it and see . . .

I know the king of blade making shows it in his videos . . . but . . . I just assume that his teacher showed him to do this as a joke . . . you know while the other old masters watched and it shocked them all when he took them seriously and did it. They just assumed the kid's common sense and primal sense of self preservation would kick in but . . . noooooooo. Luckily his knife wasn't sharp at the time or some shhhhtuff.

I don't know how people survive it. I for one have better methods.

I'm just curious . . . do you plan to keep using this "test" ?

Here is a better method. Tells me waaaaaaaaaaay more about the sharpness and geometry (biased / rolled to one side or the other; enough clearance behind the edge or not; sharp here but not there; chipped and how bad . . . etc., etc., etc.,) of an edge :



Click to expand...

The finger nail test is ok but doesn't tell much about the slicing aggressiveness. I have knives that passes this and the newsprint test pretty well but slides right off the finger or soft facial tissue.
 
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My First Rule of the Three-Finger Sticky Test: No SLIDING of the fingertips along the edge. I do it with just light enough impetus to start feeling the 'bite' of the edge on the pads of the fingertips, but not enough to make my finger actually, deliberately, slide along the edge. Sometimes a little bit of unintended slide will happen, and sometimes that'll make me bleed a little bit. But I never allow a full inch of slide along the edge, unless I'm certain it's butterknife-dull along it's full length.

If 3-finger stickiness hints at a more aggressive edge, then I'll start testing that by other means, like slicing phonebook paper. That by itself will reveal a lot about the character of the edge, by the sound and feel (whisper-quiet or 'buzzing' like a zipper), and by how/if the edge snags or slips in the paper. Attempting a cut across the face of the paper sheet, instead of into the edge of it, will also tell a lot about the edge's aggressiveness; a more polished edge is less likely to pull it off as easily.

I'm convinced all steels react somewhat differently, at least, to a given sharpening media or method. Some differences are more extreme, some are more subtle. Some will tend toward a more polished apex, and others toward a 'micro-toothy' edge, using the same stone.


David
 
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When I test three finger on a finished edge its only a few mm at the most. Enough to feel it grab the pads or not, or to feel it cut the tops of the whorls - sort of a micro-raspy feeling.
 
I see the "3 finger test" occasionally done in videos, and it's often done incorrectly. Biggest mistake is not putting the thumb on the spine first, so that the 3 fingers can be lightly placed on the edge. 2nd mistake is putting the fingers on the edge and immediately start moving them. If you watch the video...

[video=youtube;2k1o70tMHYM]https://www.youtube.com/watch?v=2k1o70tMHYM[/video]

... you'll see that (after the thumb on the spine) the fingers first touch and feel the edge, then lightly slide to check the sharpness. This better allows you to feel any change, and stop before cutting occurs. You're not feeling to see if the edge will cut, you're learning to detect what a sharp edge feels like... if that makes sense.
 
I find the S30V, S35VN types work very well with micro-serrations !
 
I honestly kind of gently tap my fingers on the edge when I'm doing the test. The natural micro movements side-to-side of my fingers is enough "sliding" for me to get feed back. Actually sliding my fingers on the edge, no less an entire inch, sounds like a cut for sure! :D :D :D

Hope you heal up quick!
 
When you use this test, you should be counting on your brain to tell you not to slide your fingers on the blade. There are a couple of guys in this thread who should NEVER use this method. Your brain senses danger in the edge, that assumes your brain senses...
That is my mature and informative addition to this thread, good night all......

Russ
 
different steel have different characteristics. one must always be careful when utilizing the 3 finger test. thus the phrase, "scary sharp"
 
mycough said:
When you use this test, you should be counting on your brain to tell you not to slide your fingers on the blade. There are a couple of guys in this thread who should NEVER use this method. Your brain senses danger in the edge, that assumes your brain senses...
That is my mature and informative addition to this thread, good night all......

Russ
Click to expand...

My brain already tells me not to do this even before I touch the edge of newly sharpened knives. :D
 
singularity35 said:
My brain already tells me not to do this even before I touch the edge of newly sharpened knives. :D
Click to expand...

I have never been worried about you, but these guys sliding their fingers up and down a blade and getting cut.... A gas station knife would do that...
Russ
 
miso2 said:
In my limited experience, I found that burr removal is easier on XHP than high vanadium carbide steels like S35VN. XHP also takes a very aggressive edge.
I don't think I can move a well-sharpened XHP blade even 0.2" over my fingers without getting blood.

Miso
Click to expand...

In my admittedly very limited experience this is exactly what I'd say of CTS-XHP. Takes such a quick and aggressive edge and is an incredibly easy to deburr steel, something very nice for folks with limited sharpening systems, methods and knowledge like me.

CAM02795_zpsvtfdewf1.jpg


That's the reason I love it!
 
The finger nail test is ok but doesn't tell much about the slicing aggressiveness..
Click to expand...

Actually it does if you focus / use the method often; the edge not only catches but sinks in a touch which makes your butt pucker. When the sphincter alarm goes off you're good. That's why The Maker wired your thumb to that other thing. Survival of the sharp knife dudes and all like that. News print ! ? ! ? Did our prehistoric ancestors have news print ? I don't think so. Couldn't afford to be shaving that heat trapping hair off all the time . . . hence the finger nail connection

I have knives that passes this and the newsprint test pretty well but slides right off the finger or soft facial tissue.
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This a sign the edge is toooooo roundy and you have a good axe grind, maybe, . . . but chances of doing city slicker EDC tasks with the edge are going to be LESS THAN I WOULD WANT. Side by side there is no comparison. Want proof ? Cut a nice sized wire tie in two with each.
Now
which do you want in your pocket ?

;):):thumbup:
 
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OK I know what you mean and I am just playing around . . . OK :o

I do it with just light enough impetus to start feeling the 'bite' of the edge on the pads of the fingertips,
Click to expand...
When your edge is "Really sharp" you won't feel anything. Later you will look and find that your fingers are off.

OK . . .I got it out. Thanks for listening. :)
 
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