Reality check

[Mark Reich]

I've been wondering for a long time when we were going to start talking about edge retention, when I came upon the closed post by Mr Mike Brubacher at the top of this index page. It's definitely worth a re-read. There was/is/should be an intended mission here that we are totally overlooking. 

I know it's fun to see low numbers on a fresh edge, but that really isn't telling much of the story. It's just the fresh dawn of the edge, or even slightly before that. Like you're still kinda in the dark. You don't know how much you can cut.

Edge retention really is of much greater significance than initial sharpness, correct?

[grepper]

Mr. Mark uttered, “Edge retention really is of much greater significance than initial sharpness, correct?”
 
I think both are important.  After all, who cares about the edge retention of a dull edge?
 
In fact, the ephemeral useful edge retention of smooth edges is what got me started on the road to toothy edges.  I had a couple of experiences trying to cut plastic rope and tomatoes where an only slightly used smooth edged blade just rode on the surface instead of cutting.  Really frustrating.  It worked great right after sharpening, but dulled so very quickly!
 
This forum used to be call edge retention, but it never seemed to get any traction or posts.  I can understand why because it’s such a difficult subject with many variables.  Designing some procedure to produce quantifiable results would no doubt be a bit of a head-scratcher.  Not impossible I suppose, but most likely far more involved than it would first appear. 
 
Much easier, albeit more subjective, would be simple real world testing like cutting a given diameter and brand of hemp rope with consistent pressure both on the knife and tension on the rope.
 
That type of test would shed some light on how well that particular knife, bevel angle, steel composition and edge finish, etc. does for exactly what was done with it, i.e., cutting rope.  But what does that mean for something like chopping carrots or other cutting tasks where there is some impact on a cutting surface?  The whole edge retention testing thing instantly raises a lot of questions.
 
That is exactly why I thought it was cool when you said you would post about how your edges did after hunting season.  That’s real, real-world testing of a blade used for a variety of tasks in the ways the user naturally uses the knife over a period of time.  While not numerically quantifiable data, it is a pretty good overall evaluation of blade performance and edge retention.  I could suffix that last sentence with …for a general purpose knife used for all the stuff a hunting/camping knife is used for.

Got any suggestions on conducting edge retention tests?

[Mark Reich]

I use 1/2" braided hemp rope because it's easiest for me to manage. The way I use it works out to 50 cuts per foot, mainly because I concentrate on cutting more than counting.

I know lots of guys cut rope. It isn't any fun, but the more you cut the more consistent you get. Actually measuring sharpness before and after making a hundred or 200 cuts should be pretty darn accurate.  

Definitely takes a concerted effort over a period of time with different knives, but it's the most accurate way for me to judge edge retention.

Counting deer is pretty accurate too, as long as you're consistent. If you're hamfistedly boning with your hunting knife you can get DQed.

Hm... time for ice cream.

[grepper]

Does a smooth edge of, say, 400 gf BESS cut rope as equally well as a toothy 400 gf edge?
 
In other words, is a before/after sharpness reading indicative of the usefulness of the edge?
 
Is the purpose of such a test to determine final sharpness or final usefulness?  Is there a difference?
 
After 200 rope cuts, have you ever seen a toothy edge with a duller sharpness reading perform better than a smooth edge with a sharper sharpness reading?
 
Does this make sense?

What results have you observed?

What kind of ice cream?  My wife makes a killer chocolate.

Have I asked enough questions?

[Ken S]

Excellent (and overdue) topic, Mark.

I just turned over 100,000 miles on my vehicle. While new car statistics may seem interesting, comparable statistics over 25 or 50,000 mile periods are really more useful.

I took a hand cut dovetailing class years ago. Halfway through the practice project, I could feel the chisel edge dulling on my O1 chisel. The instructor's Japanese steel chisel was still going strong.

Pavol Sandor has done several you tubes with an innovative rope cutting tester of his own design. Even with no understanding of Slovak, his message is clear through the visual part. You can see the results of the knife edge dulling. I highly recommend watching Pavol's you tubes. His testing procedure is very practical. His you tubes tend to be lengthy. Do not stop part way through and figure you have absorbed the jist of it. Absorb the entire you tube. See the whole picture, not just a partial snapshot.

Ken

[EOU]

BTW Mark and friends. We're still willing to spearhead an exploration into edge retention. Seems to us as if this is the next great frontier. We just didn't seem to raise much interest and input in the initial attempt. We're going to need help with this project with regard to the parameters that we are testing i.e. toothy vs polished or 150 vs 250 or steel versus ceramic or 15 degree edge vs 22 etc.. As you all know there are dozens of untested theories out there that assert both the short and long term cutting/slicing superiority of various grinds and materials. Once we know what we are testing for we can design an instrument and test bed that will provide the comparative data we are seeking.  Also BTW, thanks to everyone for making the BESS Exchange a friendly, acrimonious free, open and informative place to exchange thoughts and ideas. We've got great stuff headed your way this fall!

[Mark Reich]

I just have time for a few lines, but I want to thank everyone for sharing your interest for sure. 

While I have cut a lot of rope, I haven't had time to do more scientific research with the KN100. 

In my experience, a 1k poly diamond edge seems to work best with my 52100 on hemp rope and big game, but lately I'm finding coarser edges showing a lot of potential. The 140 Atoma edge holds well on my knives, but that's a very specific edge. I can tell you for sure it's much different than a 150 grit waterstone.

It's going to be pretty challenging to input even basic data like steel type, edge angle and grit. That's why about one person has taken the time to do significant cutlery specific research, but he adroitly minimized the variables by sharpening everything *scientifically* accurately.

I'm sure looking forward to further developments from our Outstanding sponsor! Thanks EOU!

[grepper]

Thanks Mr. Ken for passing Pavol Sandor's videos along.  He makes some interesting videos and is obviously attempting to obtain quantifiable test results and understand what is actually going on during sharpening.  All he needs is a PT50B to really complement his efforts.
 
Anyone who has checked out the microscope images and results I have posted to the Exchange will recognize what he is showing in this first video.  He then demonstrates how the burr affects paper slicing.   It’s really not a bad demonstration of how even a small amount of burr can impact edge performance.  I can’t understand a word of what is saying, but as Mr. Ken noted you don’t need to.
 
https://www.youtube.com/user/pavolko10
 
This is cool:  Here is his edge retention test machine in action.  While his test media is pretty consistent in density and size, it is one area the might be improved upon.  There is no before/after sharpness test data, but then he is not so much testing specifically for sharpness but rather how well the edge severs his test media with multiple cuts.  From my perspective, testing how well a blade continues to be useful is arguably more important than sharpness per se. 
 
That said, when testing multiple blades, initial sharpness data would definitely be beneficial.  He tests the same area of the blade, under the same pressure and has a block to prevent the edge from impact when the test is complete.  My hat’s off to him for a really impressive effort to quantify edge retention, which no doubt delivers useful, actionable results. 

You can start @ 14:00 into the video to see his test apparatus:  
https://www.youtube.com/watch?v=bfp80sYH6iw

[Mark Reich]

I did some initial testing last night, just to see how things might go. Now I think this is going to be easier than I thought.

I didn't need to get very complicated, and it didn't take long to get a surprisingly clear picture of the 140 and 400 Atoma plates, just by cutting up one little ol piece of cheap rope. I'm not sure it needs to be anything more significant than that.

I used three knives out of the same batch, to see how accurately I can sharpen and cut rope. I was trying to estimate human error, and see what kind of a range of numbers to expect. I'm happy to say the numbers were encouraging.  

Exactly, Mr Grepper! Who the heck wants to measure how dull stuff is?! Well, now it's clear that notion is a big stumbling block, and I think we've been missing out. I really felt eager to measure the blades After I'd cut rope!

Measuring initial sharpness of all three blades after the 140 Atoma showed I needed to be more careful and thorough about removing the burr. I was getting up to 230, and down to 150 on different parts of the blades. I tried two alternating passes per side +1-2*, and the apexes were clean and sharp. I could see the hint of microbevel with 10x, but they were way more uniform in the 150 range.

These blades were sharp before I started, but I still generated a tiny burr, flipped it and cut it off. One blade, a 4" Wharncliffe, only took one pass. It wasn't perfect, but I wanted to see what a quick deburring would measure. "How dull" turns out to be a pretty good question!

Any interest in how the Atomas did in a quick test?

[Rupert Lucius]

I did some initial testing last night, just to see how things might go. Now I think this is going to be easier than I thought.

I didn't need to get very complicated, and it didn't take long to get a surprisingly clear picture of the 140 and 400 Atoma plates, just by cutting up one little ol piece of cheap rope. I'm not sure it needs to be anything more significant than that.

I used three knives out of the same batch, to see how accurately I can sharpen and cut rope. I was trying to estimate human error, and see what kind of a range of numbers to expect. I'm happy to say the numbers were encouraging.  

Exactly, Mr Grepper! Who the heck wants to measure how dull stuff is?! Well, now it's clear that notion is a big stumbling block, and I think we've been missing out. I really felt eager to measure the blades After I'd cut rope!

Measuring initial sharpness of all three blades after the 140 Atoma showed I needed to be more careful and thorough about removing the burr. I was getting up to 230, and down to 150 on different parts of the blades. I tried two alternating passes per side +1-2*, and the apexes were clean and sharp. I could see the hint of microbevel with 10x, but they were way more uniform in the 150 range.
For sure we are interested -
These blades were sharp before I started, but I still generated a tiny burr, flipped it and cut it off. One blade, a 4" Wharncliffe, only took one pass. It wasn't perfect, but I wanted to see what a quick deburring would measure. "How dull" turns out to be a pretty good question!

Any interest in how the Atomas did in a quick test?

---

For sure we are interested

Rupert