Under the microscope

[Clip]

Hi Clip,

Thanks for your reply. :)

My tungsten-carbide blank, is one used for metal-shop, so it is definitely one of the tungsten-carbide-cobalt types. (ie: not pure tungsten carbide.) The blank is often used to make jointer or planer blades in wood-shop, or used to make cutting bits in metal-shop.

My understanding is that a pure tungsten-carbide bit would be too brittle for metal-work. So they give up some hardness and gain some toughness by going to tungsten-carbide particles in a cobalt binder.
http://en.wikipedia.org/wiki/Cemented_carbide

Not that I actually know the details; I just read too many wikipedia articles and poke around science papers.

Sincerely,
--Lagrangian

Thanks for the info! I, too, spend a lot of time on Wikipedia :) We've had to work with some solid WC plates and they were awful about chipping/spalling. I wasn't aware that you could get blanks for those planer/jointer blades but now that I think about it, it's very obvious. Pictures of the aluminum foil to be posted tonight!

[Lagrangian]

Hi Clip,

Wooo! Aluminum foil! :)

Sincerely,
--Lagrangian

[Clip]

Reynolds Heavy Duty aluminum foil, shiny side first then matte.

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Matte

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[Lagrangian]

Wow! Thanks Clip! :)

Sincerely,
--Lagrangian

[Lagrangian]

Hi Clip,

I'm wondering if you and your microscope are able to take the following type of pictures:

The microscope looks directly into the cutting edge of the knife. That is, if you got the microscope lense too close, the knife would actually cut into the lense. The reason for doing images like this, if possible, is to measure the actual sharpness of the knife. Prof. Verhoeven did this using an electron microscope, which has an insanely huge depth of focus. I understand, of course, that optical microscopes have a ridiculously shallow depth-of-focus. But since your setup can automatically generate and combine multiple images that are focused at different heights, I thought maybe you could take an image where the top 0.5 microns of the knife apex was in focus.

Here is an example photo from Prof. Verhoeven's technical report _Experiments on Knife Sharpening_ (2004).
http://www-archive.mse.iastate.edu/file ... ShExps.pdf
In this photo, he is actually able to measure the sharpness of a modern razor. He measures it to be from 0.35 to 0.45 microns. In case the image is confusing: The microscope is looking straight into the knife edge. The diagonal line from top-left to bottom-right is the knife edge itself. And the two bevels of the knife are on either side.


I don't expect you to be able to have such insanely huge depth of focus. But if you can capture just the top micron or so, that would be enough. Is there any possiblity you could do something similar? If your sample size has to be small, maybe not for a full sized knife, but you could break off part of a razor blade (or any cheap $5 knife from Walmart) to make it small enough.

Ah sorry, Clip. I keep thinking of more work for you to do, all the time! :rolleyes:

Sincerely,
--Lagrangian

[MadRookie]

...wow....how technically deep are you guys going to go....my head is spinning as it is....?????

NICE!!!

:)

[BAL]

Great stuff.

[phillipsted]

That picture on the left looks like an satellite photo of Mount Everest!

TedP

[Lagrangian]

That picture on the left looks like an satellite photo of Mount Everest!
TedP

Just for fun:

A human being is about 2 meters high.
Mount Everest is about 8,800 meters high.
So Mount Everast is about 4,400x times taller than a person.

A knife edge is about 0.4 microns sharp.
So compared to a knife edge, a person is 2/(0.4*10^-6) = 5,000,000x bigger than the knife edge.

If the knife edge were a mountain-climber, and he needed to climb a human being, then how tall of a mountain would that be? Doing the calculation: 8800*(5,000,000/4,400) = 10^7 meters. So, to a knife edge, a person is a mountain 10,000 kilometers tall.

In othewords, to a knife edge, a person is a mountain so huge, it is taller than the length of a continent!

If that did not blow your mind, I think it should. Because when we are sharpening, we are forming an edge so much smaller than ourselves, it is like a world continent reaching out to grab the huge island of Madagascar (1,570 km) and sharpening it down to an apex the size of a single human being (2m). How would a giant the size of a continent even notice the single person at the apex?

And yet, experienced knife users can tell when their edges are scary-sharp (sub-micron) versus not (maybe a several microns).

Sincerely,
--Lagrangian

[razorsharp]

Just for fun:

A human being is about 2 meters high.
Mount Everest is about 8,800 meters high.
So Mount Everast is about 4,400x times taller than a person.

A knife edge is about 0.4 microns sharp.
So compared to a knife edge, a person is 2/(0.4*10^-6) = 5,000,000x bigger than the knife edge.

If the knife edge were a mountain-climber, and he needed to climb a human being, then how tall of a mountain would that be? Doing the calculation: 8800*(5,000,000/4,400) = 10^7 meters. So, to a knife edge, a person is a mountain 10,000 kilometers tall.

In othewords, to a knife edge, a person is a mountain so huge, it is taller than the length of a continent!

If that did not blow your mind, I think it should. Because when we are sharpening, we are forming an edge so much smaller than ourselves, it is like a world continent reaching out to grab the huge island of Madagascar (1,570 km) and sharpening it down to an apex the size of a single human being (2m). How would a giant the size of a continent even notice the single person at the apex?

And yet, experienced knife users can tell when their edges are scary-sharp (sub-micron) versus not (maybe a several microns).

Sincerely,
--Lagrangian

geek :p :)

(though Im a steel and sharpening geek lol )

[BAL]

That picture on the left looks like an satellite photo of Mount Everest!

TedP

Yea, and it looks like that might be a Yeti den on the near side of the mountain.

[jackknifeh]

Just for fun:

A human being is about 2 meters high.
Mount Everest is about 8,800 meters high.
So Mount Everast is about 4,400x times taller than a person.

A knife edge is about 0.4 microns sharp.
So compared to a knife edge, a person is 2/(0.4*10^-6) = 5,000,000x bigger than the knife edge.

If the knife edge were a mountain-climber, and he needed to climb a human being, then how tall of a mountain would that be? Doing the calculation: 8800*(5,000,000/4,400) = 10^7 meters. So, to a knife edge, a person is a mountain 10,000 kilometers tall.

In othewords, to a knife edge, a person is a mountain so huge, it is taller than the length of a continent!

If that did not blow your mind, I think it should. Because when we are sharpening, we are forming an edge so much smaller than ourselves, it is like a world continent reaching out to grab the huge island of Madagascar (1,570 km) and sharpening it down to an apex the size of a single human being (2m). How would a giant the size of a continent even notice the single person at the apex?

And yet, experienced knife users can tell when their edges are scary-sharp (sub-micron) versus not (maybe a several microns).

Sincerely,
--Lagrangian

Did all that thinking hurt? :) Did it leave a mark? :) I thought Madagascar was a children's movie. :)

Seriously, that's an interesting way to illustrate how small a knife edge is and that to some people (who think about it) there is still a big difference between a scary sharp edge and a very sharp edge. Sometimes a very sharp edge just isn't sharp enough. :mad: We want scary sharp. :D

Jack

[Lagrangian]

Did all that thinking hurt? :) Did it leave a mark? :) I thought Madagascar was a children's movie. :)
Jack

What?! :p I was giggling like a little child all the way through! :)

Sincerely,
--Lagrangian

[Donut]

If that mountain analogy were a good one, you would either have to use a pretty horribly thick knife edge or have to use a very short human being.

You can't use a tall human and a very sharp (small) edge.

[Clip]

I tried to turn the knife upright and it didn't show as much as I hoped. Too much light was reflected off the sides and away from the lens. I'll try to get pictures but they won't be anywhere near the quality of the ones posted above.

[Lagrangian]

Hi Clip,

Ah, sorry to hear it was very difficult. But thanks for trying! :) And we look forward to any images, even of the failed attempts to image the very very edge of the knife. The failed attemps would show us something important about the limits of modern optical metallography microscopes, even with digital processing of mutliple-image stacks.

Sincerely,
--Lagrangian

[connor]

@Clip

I would like to request a few pictures of a blade/steel of your choice with a deliberately rolled edge (e.g. steeled/sharpened from one side only for ~20 strokes) just so that we can see how that looks on a microscopic level.

Thanks in advance,

Connor

[Clip]

It's been forever! Got my Edge Pro Apex with the Choseras yesterday and polished up the 154CM Manix2, which already had a decent edge from the Lansky. Matched the angle and went through the 220 EP, 400 C, 1K C, 3K C, 5K C, and 10K C with a light stropping on green compound, then etched with Kaellings quickly to try and give some definition.

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[xceptnl]

It's been forever! Got my Edge Pro Apex with the Choseras yesterday and polished up the 154CM Manix2, which already had a decent edge from the Lansky. Matched the angle and went through the 220 EP, 400 C, 1K C, 3K C, 5K C, and 10K C with a light stropping on green compound, then etched with Kaellings quickly to try and give some definition.

Chris, those finishes look way smoother and the EP seems to make a significantly smoother finish cutting edge. Thanks for your continued update photos. As "connor" stated in a previous post, it would me nice if you could post closeups of any edge issues you experience (rolls or chips). I'm sure 100s of other forum members would gain understanding from such intimate images with the cutting edge.

Landon

[Clip]

Absolutely, I'll throw that knife in my pile to take to work tomorrow and subject it to some abuse. Sorry it's taken a while Connor!