I wish someone with a collection of stones, would polish small bit of mild steel so we can compare fineness, between natural and synthetic.

[SliceOfLife]

Don't think much of anything gets shinier than an 8k DMT polish... but you don't wanna shave off it.

Also, steel grade is gonna impact results, so results on mild steel wont be the same as on razor-grade steel.


Edge geometry @ 200x+ is a pretty useful indicator of a stones quality in my experience; but not absolute (8k DMT a good indicator of this, or 1200 DMT for that matter... bullet-path straight edges, but too fat to shave with)... and scratch pattern is basically worthless as an indicator. Absolute trash slates can leave a really clean scratch pattern; but annihilate the edge. Ultra hard/slow stones like agates can do this too. Brilliant mirror shine, but so slow the edge takes a beating from the act of honing and degrades even as the bevel gets shined up like crazy.

 

[eKretz]

Don't think much of anything gets shinier than an 8k DMT polish... but you don't wanna shave off it.

Also, steel grade is gonna impact results, so results on mild steel wont be the same as on razor-grade steel.


Edge geometry @ 200x+ is a pretty useful indicator of a stones quality in my experience; but not absolute (8k DMT a good indicator of this, or 1200 DMT for that matter... bullet-path straight edges, but too fat to shave with)... and scratch pattern is basically worthless as an indicator. Absolute trash slates can leave a really clean scratch pattern; but annihilate the edge. Ultra hard/slow stones like agates can do this too. Brilliant mirror shine, but so slow the edge takes a beating from the act of honing and degrades even as the bevel gets shined up like crazy.

Yep, no lie. I figure to do both just so the guys interested in polishing the sides of a knife or sword might get some info too. The images obviously don't always tell the story in terms of whether an edge is going to shave well or not, but at least we should be able to get a very good indication of whether the apex is formed straight and uniformly, rather than ragged. For instance, a Feather blade is generally arrow straight even at 400x. I intend to do a little more experimentation with wire/burr removal when I get a chance too. Much easier to get a better look at what's going on with the apex with a scope like this.

 

[eKretz]

Since I had a minute I threw up a couple quick images of a Feather AC Pro blade. Annotations should be self explanatory. All of these are at 400x optical but slightly cropped. This is still the backlit method, of course.

And to compare, two images from a pretty hard and fine JNat. First straight off the stone, second with a few swipes on a 0.1 micron CBN strop. This I think shows how very thin and wispy the last bit of the apex is off the stone as it straightens out almost to the extent of the Feather blade with very few strokes. And wow, cleaning the optics really helped, haha. The latest images are missing all the black dot accessories from the JNat ones...

Here's a shot of a calibration slide that's cropped about the same as the above shots so you can see approximate field of view too. Need to superimpose these eventually.

 

[eKretz]

Was just fooling around with the microscope tonight after disassembling the whole thing the last several days to clean optics, as well as clean and relubricate all the moving bits and was looking at a few things afterwards, and saw something pretty neat. This is a bit of rust on a beater blade at 200x. First picture is regular brightfield illumination. Second picture is polarized light. It really makes the rust pop.

Plain Brightfield

Polarized Light Brightfield

 

[eKretz]

Now that the optics are nice and clean things are looking a little better. This scope has an intermediate optical magnification booster built in with 4 levels in a range of 2.5x to 5x so you can increase magnification for the eyepieces and camera ports - this is helpful so that you can get higher zoom levels but still keep a good depth of field. So a few more images from when I was playing with that today.

Here is a brightfield image of 500x optical magnification, the red bracket is the approximate width of the field that you will see in the next images using the booster. Field of view here in the eyepiece is about 520μ or so:

This is that region highlighted in red on the image above. This equates to about 1,200x optical magnification. It can go higher but resolution suffers. This is about the highest somewhat useful magnification. Field of view is about 135μ or so, cropped slightly to remove round edges from the 1,200x optical frame:

Here is the same region in darkfield:

Now a shot of a calibration slide at the boosted ~1,200x magnification with 10μ graduations:

And one more at max magnification, equivalent to ~4,000x. You can see this wouldn't be of much use due to the fuzziness. Again, 10μ graduations, eyepiece field of view about 64 microns:

 

[eKretz]

And another cool polarized light shot. This is one of my daughter's highlight bleached hairs under polarized brightfield lighting. The magnifications are 100x and 200x. The dark region is where the bleach apparently didn't work.

100x

200x

 

[Herrenberg]

This is amazing stuff. I hope you will keep going.

Naturally, I now covet a metallurgical microscope. But wow, the pricing! Know any good ways to pick up a used one?

 

[eKretz]

Not really, I just got lucky and kind of fell into mine. You might try watching eBay or checking out some microscopy message boards that have got for sale sections. I've heard that university surplus stores have great deals at times too. Trying to ship a microscope like this from eBay is a little iffy if you don't get a good seller though. Mine weighs about 100 pounds. And there are a lot of intricate little pieces that tend not to still be there since they often get separated and/or lost at some point. So a lower cost scope might be a gamble. There are some lower cost versions out there, just gotta be vigilant. I looked for quite a long while before finally finding mine, then ended up with two very nice microscopes in a matter of weeks.

There is a little less complicated Olympus version called a BHM that is a pretty good scope too, they come up now and again for a good price. The good quality objective lenses are still pretty expensive though - and those make a difference in image clarity at higher magnifications.

I am going to try to get a good DSLR camera set up soon, then I should be able to get even better images. I have a trinocular camera set up right now but I don't care for it much. I think it needs an auxiliary lens (0.35x) to work a little better. Trying to locate one of those now. May take a while...haha. in the meantime using the eyepieces the images are crystal clear, sometimes I get a good shot with my phone camera through the eyepiece and sometimes not. I will start doing some image stacking once I get a good camera set up, then the images should really pop.

 

[cotedupy]

This is A+++ content. Great stuff!

Would you be able to take any shots of stones or mud? That'd be very interesting too...

 

[SliceOfLife]

I snagged one (A kind of home version) on eBay a few years ago with less features, but the lamp is a no go and replacing it costs more than the scope did. Optics had some dust I couldnt get rid of even by disassembling/cleaning (couldnt find it) too... but I replaced them recently so once I'm back up and running (with ~$150 into this thing), it'll take cleaner pics like these. No intermediate optical mag though. I can get up around 8000x through digital mag (take a high res pic and put it on a big monitor), but there's obviously problems with that as digital magnification always involves some guessing or approximation.

Also, what did you do to that poor feather? Tell me that wasn't done just by shaving with it.

You should add some post-leather stropped images of the same (jnat and CBN) edges to compare.

 

[eKretz]

Yeah the dust on neglected scopes can really be a pain, and it can pretty badly cloud the image especially if it's on several consecutive lenses in the system. Some of them can be a real bear to get to also. I had this scope completely apart for days. In the base there's a complicated system of neutral density filters that click in and out in different combinations to adjust the lighting intensity. There are two more filters for changing the lighting hue from halogen bulb yellowish to more of a white color. There's a mirror and a diffuser to switch from reflected light to transmitted light like a biological scope. There's another window with anti-reflective coating. In the middle there's a module that has about 10 more mirrors and lenses in it. In the top there's another batch of probably 15 more lenses, mirrors and prisms. When cleaning you also have to be very careful of damaging lens coatings, especially so on older lenses.

The Feather blade was like that out of the box! The damage from end to end is only of a length about equivalent to two stacked pieces of paper though. I'll try to get some more images of the JNat edge post-shave. I can do some images of stones and such too. I think I will start a new thread just for microscope images of edges and other stuff. Feel free to join in! Hopefully we can keep it going a while. I asked @alx gilmore to join in too.