Understood Clay, and I think that's a great thing. Just pointing out there may be (I don't really know) a point where more magnification isn't more helpful.

But you'll figure it out if true.

Ken

wickededge wrote:


I was going to say you're just a big tease... but in this case, I guess you're a little one!

Hi Clay,

Have you considered a contact profilometer at all? It's a device used to measure surface-roughness, and is typically used in some metal-working and/or machine-shops. It runs a tiny stylus over the surface and reports back a numerical measurement. The "advantage" is that while it is very expensive (thousands of dollars), it is not insanely expensive (like an scanning electron microscope). The downside is that it returns numbers, not an image. Or, I suppose, it may return a single line of data as a graph (ie: a 2d plot where x-axis is horizontal position of the stylus and y-axis is the stylus height). So it's not as simple to interpret the results. And if the surface is directional (like lots of parallel scratches), then the scanning direction will affect the results.

There are non-contact profilometers; they're typically based on light scanning. But non-contact profilometers are insanely expensive (at least from what little I've heard).

I know almost nothing about profilometers, except what I've read on wikipedia:
en.wikipedia.org/wiki/Profilometer
en.wikipedia.org/wiki/Surface_metrology

Example of a contact profilometer by Mitutoyo (high quality Japanese company):
www.amazon.com/Mitutoyo-178-561-02A-Surf...=pd_sim_sbs_indust_1

Probably not worth buying. But if you have any friends who work in a lab for manufacturing, machining, or metrology, it might be worth asking them for a favor?

I kind of got curious about metrology in general, and got sucked into browsing Wikipedia for hours and hours.

Sincerely,
--Lagrangian

This is fascinating. I'd never even heard of a contact profilometer before. It might be what CoorsTek uses for their stones since they measure in RA (roughness average). I'll definitely check them out. Thanks for the tip!

AnthonyYan wrote:

While not pretty to look at at 2000x, here is another image of a blade that I polished mostly smooth and then used the fine side of the Micro-Fine ceramics to lay in a a scratch pattern:



The fine scratches going from lower left to upper right are left over from the kangaroo strops with .5um diamond spray. The couple of big scratches coming from lower right to upper left are from the Micro-Fine stones. I took 4 measurements: .57um, .64um, .68um and .72um. I calibrated my scope and the lens with a NIST traceable stage micrometer so I feel confident about the accuracy of the measurements inasmuch as I could find the correct edges of the scratches to measure. As can be seen in the photo below, those edges can be tricky to choose and can affect the measurement by +/- .05um:



I really wanted to verify the grit of these stones since I've had questions since they came in. I'm happy to report that they look spot on to my amateur eyes.

Awesome! The one I'm curious about though is the MicroFine - Coarse. I think that's the one that seems rougher than rated.

cbwx34 wrote:


That's next on the chopping block I'll go back through with the kangaroo strops and smooth out the bevel and then use the Micro-Fine - Coarse stones and see what we get.

Here is the first look at the Micro-Fine - Coarse stones:



I'm surprised not to see more work done and I'll have to go back and get after it a little more. I did complete 50 strokes, starting from a very smooth bevel. In this photo, you can still see bits of Sharpie marker in the low places since I didn't clean it with alcohol before putting it under the microscope. I measured the largest of the scratches and they averaged between 1 and 2 microns.

These next two images explain a lot:


Above - 150 strokes with the Micro-Fine 1.4um Coarse Side stones LAPPED to 3um on diamond plates


Above - 50 strokes with the Micro-Fine 1.4um Coarse Side stones NOT LAPPED

The scratch size is in the right range with both stones but the depth of the scratches is greatly exaggerated with the unlapped stones.

I'm getting better with the software provided with my scope. Here is a shot of the blade after the Superfine - Fine stones, 50 strokes:



The scratches are in the 1.5um-3um range.