Reality check

[grepper]

When Mr. Mark uttered, “Edge retention really is of much greater significance than initial sharpness, correct?”
And I replied,
“I think both are important.  After all, who cares about the edge retention of a dull edge?”
 
What I was trying to say, however ineloquently and inadequately, was that if you have a dull, useless edge to begin with there is not much point in testing its edge retention. 
 
Actually, I’m in complete agreement with you.  It is not only interesting but essential to take sharpness measurements after stressing the edge so as to compare the initial sharpness to the sharpness after stressing the edge.  So, yeah, you could say that after stressing the edge the second sharpness test, and all those that follow is testing for dullness, or maybe more precisely, an increase in dullness.  The comparison of sharpness readings before and after stressing the edge is obviously one measure of edge retention. 
 
That said, I think sharpness is only one side of the edge retention equation.  The other is how long the edge is useful for a particular task.  Slicing tomatoes is a good example.  In my experience an only very slightly dull smooth edge starts riding on the skin, while a toothy edge continues to cut well much longer.  That’s why I think edge retention testing and interpreting the data is more difficult that it first appears.   
 
Mr. Mark teased, “Any interest in how the Atomas did in a quick test?”
 
Please take pity.  The suspense is killing me! 

[grepper]

I have done no testing to verify this but I have a suspicion, a wild guess, that a toothy edge with a less sharp (duller) sharpness reading may perform better at some tasks than a smooth, very slightly rolled edge with a sharper sharpness test reading.

That would indeed be interesting to find out.  

It's why edge retention is puzzling to me, and what it really means and how exactly to test it.

[Rupert Lucius]

I have done no testing to verify this but I have a suspicion, a wild guess, that a toothy edge with a less sharp (duller) sharpness reading may perform better at some tasks than a smooth, very slightly rolled edge with a sharper sharpness test reading.

That would indeed be interesting to find out.  

It's why edge retention is puzzling to me, and what it really means and how exactly to test it.

Grepper,  my feelings are your feelings/writtings at this juncture in ref to the above said.

Thanks, for stating my feelings so eloquently.

Rupert

[grepper]

Mr. Mark temptingly queried, "Any interest in how the Atomas did in a quick test?"

Yes!  Please kindly deliver us from this agonizing anticipation!

[Mark Reich]

Sorry, I forgot about the last holiday of summer. We had a great little vacation, and I hope everyone had a fun weekend!

I was sort of teasingly trying to gauge interest in edge retention tests. Like EOU explained, edge retention testing doesn't seem to be gaining the traction it should. I'm happy we have other things to talk about, but I was hoping we would get around to it eventually.

I was hoping to show that retention testing doesn't have to be complicated or all encompassing. Every little bit helps. Whatever anyone has to offer, it's welcome here. Nothing has to be perfect. It's not a competition.

I had to do my testing over this morning. I thought I could remember, but I wasn't planning such a hiatus. As I was working, it did start coming back to me. The results were pretty darn repeatable.

With a little more learning and practice, I'm getting consistent working sharpness of 120 KN100s without any fooling around at all. I just do a normal quick touch up, and Bam, 120. The surprising thing is it doesn't matter if I'm using the 140 or the 400. What's more, after 100 cuts, they are both measuring about 250! 

Maybe there is a different feeling when going through the rope that would match my intuition. I think so, but it will take more cutting to say with confidence. 

The testing really isn't grueling or boring. It just takes quite a bit of time, which I'm sorry to have so little of.

[grepper]

Thanks Mr. Mark.  “The surprising thing is it doesn't matter if I'm using the 140 or the 400.”  
 
I’ve noticed the same thing.  Grit does not seem to matter that much.  It’s just a matter of how toothy you want the edge to be.
 
A few questions:  What steel are you using?  Do you know what hardness?
 
Are you accounting for the 50g weight of the KN100 piston?  Am I correct that you have posted before that when you say 120 that is only the weight added to the piston?  That would mean that from a PT50B point of view, the reading would be 170.
 
Aside from sharpness, cutting tomato skin is another good test.  I’ve found that smooth edges start riding on the surface quite quickly while the more toothy flavor of edges keeps slicing.  I have yet to find anything that demonstrates that edge difference better than the good old tomato test.
 
I think that the task the knife is going to be used for has to be one factor when considering edge retention.

"I was hoping to show that retention testing doesn't have to be complicated or all encompassing. Every little bit helps. Whatever anyone has to offer, it's welcome here. Nothing has to be perfect. It's not a competition."

I completely agree!  Well stated.  When you have time, I'm looking FW to your further results.  Thanks for the effort and for sharing.