Native flat to the stone & pushcuting newsprint vs. yellow pages observations

[gunmike1]

Here are the new results for the Native. Again, flat to the stone with a 15 degree microbevel. All measurements are distance from the point of hold to pushcut the yellow pages.

Spyderco Fine: 2.82" ave., worst cut 2.66", best cut 3.04"

Spyderco Ultrafine: 2.95" ave., worst cut 2.75", best cut 3.11" (twice)

So the edge definately increases in pushcutting sharpness as you go up to Spyderco Fine and Ultrafine finishes from the medium, but the jump isn't really that big. I need to test it out on cardboard or something similar now for edge durability. As it is there are a couple spots where there are chips in the edge from when I was honing flat to the stone and went all the way to the edge with the really coarse stones. After some cardboard testing I will try to minimize some of those with some flat to the stone work on the DMT 600, but they don't really effect the cutting ability and I have been short on time.

Also, for reference, I sharpened a factory edged Native 3 at a 20 degree microbevel and got these results:

Spyderco Fine: 1.81" ave, worst cut 1.66", best cut 1.93"
Spyderco Ultrafine: 2.10" ave, worst cut 2.05", best cut 2.17"

More proof that it is much easier for me to get good sharpness results on a very thin and acute edge. The Native 3 was between 13.9 and 15.7 degrees along the edge, with a thickness of .019" to .021".

 

[sodak]

Good results on both knives, but yeah, thin is in!

 

[Cliff Stamp]

Interesting results, I would wonder if it isn't showing an influence of cutting ability as the results are very close to the angle ratio.

-Cliff

 

[gunmike1]

Interesting results, I would wonder if it isn't showing an influence of cutting ability as the results are very close to the angle ratio.

-Cliff

I was thinking the same thing, as they both seem to shave equally well, but I never thought cutting ability would come into play with the yellow pages, as they are so thin. I really need to find myself a kitchen scale and some thread so I can get some more repeatable results that take the cutting ability out of the equation totally and just measure the sharpness, but I make due with what I have. I also sharpened the Native 3 after the Native, without cleaning the stones, so that may be part of the difference, but on both knives the stones seemed to be cutting similarly and didn't appear to be loaded up with steel.

 

[Cliff Stamp]

Cutting ability should influence the sharpness measurement in all cases as there will always be issues of binding and such. It did surprise me there, though as you noted, that it was so large.

-Cliff

 

[gunmike1]

Cutting ability should influence the sharpness measurement in all cases as there will always be issues of binding and such. It did surprise me there, though as you noted, that it was so large.

-Cliff

Part of the issue is that I don't consider it a pushcut unless the knife can continue the cut through the material. Sometimes a knife will make a very shallow cut, but I don't count those unless they can continue through the material.

 

[thombrogan]

Jeff Clark noted the relationship between sharpness and cutting ability both directly and indirectly his monumental thread on bragging edges and Goo notes that geometry is highly important as well.

I think the observations you and Mike Swaim have made about the relationship of sharpness to cutting ability are both highly educational and slightly flawed. In my own, corroborating experience, I had an Extrema Ratio brand Nemesis folding pocketknife which could pop hairs and dice the ends soft-drink straws (and behead daisies) with the best of them, but it had a thick edge which quickly ran up to a 0.23" thick blade. That doesn't mean that sharpness is a property independant of geometry/cutting ability as much as it means that straws, daisies, and hairs have a much wider tolerance of sharpness than other materials.

While Juranitch doesn't state such a relationship (maybe due to his tempering his intellectual curiosity with anti-intellectual rhetoric), but please note that the included edge angles on his resharpened axe and knife were 20 and 12 respectively. The axe was explained as having 10 degrees per side for durability. Emphasis not added for the benefit of Cliff Stamp, Gunmike1, or Sodak amongst others).

 

[gunmike1]

I love that link! The funny thing is that when you properly sharpen a knife, and make sure there is no burr, even a "working edge" like a Medium Spyderco finish will easily pop my hairs. If I remember right Cliff put a ridiculously coarse edge on some CRKT's and was pushcutting newsprint well away from the point of hold and shaving smoothly with it. Spyderco's factory edges are very toothy, but since they form them clean they are very good at pushcutting also. But yes, I like to put highly polished edges on my knives and get better pushcutting performance, but as Cliff has pointed out the more acute the edge, the more toothy the edge is at a given finish. Thus, you would expect those of us who love thin edges to want to put a very high polish on our knives. Not to mention, when they pushcut that good it makes up for a lot of the loss of slicing aggression, but unless you were doing a marathon session of cutting rope or cardboard I don't think you would be at too big of a deficit for EDC stuff by going for the show off edge.

By the way, Thom, under magnification your edges have much smaller microserrations than the Spyderco UF finish, so those .3 micron Mylar abrasives do their job very well. Plus, it seems to shave hair above the arm a little better than my Native. So, my yellow pages tests do give repeatable feedback on sharpness, but I still would prefer a scale and thread set up, as it takes a lot of variables like technique with the paper and variation of the paper out of the equation, or at least improves upon those issues.

 

[thombrogan]

It will take out a lot of issues, but performing a straight pushcut or a skewed pushcut or a slightly slicing version of either should change the results so it's a factor to watch.

The 0.3 micron finish you're experiencing is quite a big jump from the 5 micron scratches before it. Don't know which ones you're seeing, though. It may work even better if I can get ahold of some 1 micron film and use it as an intermediate step between the 5 and 0.3 micron films.

 

[gunmike1]

I always try to do the pushcut straight down, but holding the paper in one hand and the limits of my dexterity will obviously lead to some variation. That is why I do several cuts and average them, but the anal retentiveness in me thinks the thread test would be better. The cheap ass in me says the phone book is free, though, so my neurotic sides will have to duke it out to see which one wins.

As for the scratch pattern out of memory you could definately see some areas with larges micro teeth, but there were a lot of areas with extremely small microteeth. Overall they were a decent bit smaller than the micro teeth on my Native.

 

[sodak]

It will take out a lot of issues, but performing a straight pushcut or a skewed pushcut or a slightly slicing version of either should change the results so it's a factor to watch.

The 0.3 micron finish you're experiencing is quite a big jump from the 5 micron scratches before it. Don't know which ones you're seeing, though. It may work even better if I can get ahold of some 1 micron film and use it as an intermediate step between the 5 and 0.3 micron films.

Thom,
I've got some diamond paste in 1, 0.5, and 0.25 micron. Holler if you want some, always fun to play.

Gunmike1,
Interesting results! I always have a hard time distinguishing between sharpness and cutting efficiency on some of my thiiiiiin blades. They can be dull to the point of not being able to scrape my wife's back hair without waking her up, but still cut well.

 

[thombrogan]

I've got some diamond paste in 1, 0.5, and 0.25 micron. Holler if you want some, always fun to play.

Got some in 0.5 myself. Fun on a computer paper over glass strop, I'll tell you what! Still looking to get the most out of it on a paper tape blank in my EdgePro, too. Also just got a D8EE and need to wear away the poorly-bonded diamonds. Tonight, I touched up my ZDP Delica with the D8EE (including polishing the primary) and stropped with 1 micron AO polishing cloth over glass and the edge seems sharper and more durable than it has even been. It cut through an empty gallon bottle of apple juice (thick, multi-angled plastic) without any chips to be felt or seen. Edge seemed flatter than when I use an 8K Norton, too.

They can be dull <snip/>, but still cut well.

I've argued it to Cliff and I'll argue it to you, but I think that cutting ability and sharpness are patterned-welded in a random damasc pattern of context. Hair has a tight tolerance for unaligned edges, but a sloppy tolerance for edge thickness whereas other materials (cardboard, plastic, puppies, wood being split versus felled) will respond more to the width and/or polish of the blade. Sharpness, like certainty, is contextual. Of this, I'm certain. Along with the material being cut, the type of cut also determines if the edge is sharp or not. We have pushes, pulls, arcs, and skews containing all three.

 

[Cliff Stamp]

In my own, corroborating experience, I had an Extrema Ratio brand Nemesis folding pocketknife which could pop hairs and dice the ends soft-drink straws (and behead daisies) with the best of them, but it had a thick edge which quickly ran up to a 0.23" thick blade. That doesn't mean that sharpness is a property independant of geometry/cutting ability as much as it means that straws, daisies, and hairs have a much wider tolerance of sharpness than other materials.

You can define the word to any particular description, I choose geometry independent because of the ability to separate thickness from edge quality. Without this line of thought there is mass confusion about the origon of the performance.

... a ridiculously coarse edge on some CRKT's and was pushcutting newsprint well away from the point of hold and shaving smoothly with it.

Yeah, Joe illustrated that years before I did as well. The SRK review was the first clear arguement I saw for coarse edges being able to be very sharp in regards to precision cutting. Swaim argued something similar.

Along with the material being cut, the type of cut also determines if the edge is sharp or not. We have pushes, pulls, arcs, and skews containing all three.

No need to argue that to me, I have made the same arguement myself which is why I have been measuring push and slicing sharpness for years independently.

-Cliff

 

[thombrogan]

I'm trying to figure out a highly effective device which lets folks realize that their seemingly spooky-sharp Extrema Ratio Nemesis or stock-thickness Cold Steel Voyager X2 may be 'sharp' for some tasks and not sharp enough for others. At this point, aside from preaching to the Johnstonians, Talmadgeen, Stampites, and similar Farengi, my only recourse is the Cold Steel Shovel and that indicates a failing on my part because if I can't communicate, I don't understand (either not understanding the topic; not understanding that some folks already know everything; or a combination of the two). Who cares? Not me and my shovel!

 

[Cliff Stamp]

Slice a turnip and then slice a tomato. One of these is highly sensitive to geometry and almost ignores sharpness and the other is highly sensitive to sharpness and almost ignores geometry.

-Cliff

 

[thombrogan]

Do potatoes count?

Gunmike1,

I'm going to have thin out my Native now. Well not right now, but very soon.

 

[gunmike1]

Gunmike1,

I'm going to have thin out my Native now. Well not right now, but very soon.

Hah!, you're too late to match me now! I just talked to Tom Krein and the Native is on it's way back to me with the hollow raised up well into the opening hole and the edge in the .007"-.008" range. Now it should really cut like a champ, and hopefully the S30V can take it. We'll see. I'll post some pics when I get it back. Tom said it turned out real nice, and that he rounded off some sharp edges on the choil to make it a little more comfortable. On a similar note, Cliff's Jess Horn ZDP now has the hollow raised and an edge <.005", same for the Meadowlark Cliff sent me. Tom Krein is the man! Now I need to get off my butt and start testing these bad boys. I need to talk to the sister in law about getting some free cardboard and I need to get some rope for slicing tests.

Mike

 

[Tom Krein]

Cliff,
Give me a call if you can or send me your phone number.

I have a little something for you!!

Tom
479-736-3444