Micron size of Spyderco UF stones?

theonew

theonew

Joined
May 16, 2006
Messages
2,724
I've been finishing all my knives using a Spyderco UF ceramic for over a year. I've been very happy with the results, near mirror polish, finished edge easily whittles hair. But recently thanks (:rolleyes:) to some BF members (you know who you are :D) I've decided to raise the bar a bit and get closer to atom splitting sharpness. Up until today I've assumed that the Spyderco UF had an abrasive size of 3 microns. A few years ago I bought this combo waterstone 1000/6000. According to my cobbled together information on grit sizes 6000 japanese should have an abrasive size of 2 microns. So I lapped the 6000 side, it really needed it, and took an already hair whittlingly sharp edge and started sharpening it. First thing I noticed was that it felt a good bit more abrasive than the Spyerco UF. After 20 or 30 strokes per side I rinsed off the knife and noticed that the almost mirror polish it used to have was quite degraded, looked to be somewhere between the UF and a DMT EF. It almost whittled hair but didn't. So now it would appear that either A) the Spyderco UF has an abrasive size which is less than 2 microns or B)the 6000 grit waterstone I have, is much coarser than the 2 micron size I believed it to be. Anyone have any thoughts? Thanks.
 
Sal says that the UF is 3 microns, but it works like a 12k stone (1.2 micron) for whatever reason. The razor honing community puts it up at 12k grit, the Naniwa 12k and Shapton 16k is a little finer so that is what would come after the UF. Both those stones give an even shinier mirror polish.
 
The spyderco UF is 3 microns or very close to it, waterstones are going to leave a different finish and also have a different shape of abrasive so the results will be different. The spyderco UF is only considered 12k by the razor community because they re-lap it.

Different stones give different finishes and different levels of sharpness. I recently read something that also stated that a good waterstone will not leave a perfect mirror polish but a finish that has a haze to it even though it is very fine. I find this to have some truth because even with my 8000 grit waterstone its not a perfect mirror polish or even one that is equal to the finish of the UF ceramic.
 
Waterstones measure grit differently than sandpaper's grit, 30000grit in terms of waterstones is equivalent to 12000grit on sandpaper, both are 0.5microns. Microns is the only measurement that doesn't change when you use different type of stones.
 
Roger999 said:
Waterstones measure grit differently than sandpaper's grit, 30000grit in terms of waterstones is equivalent to 12000grit on sandpaper, both are 0.5microns. Microns is the only measurement that doesn't change when you use different type of stones.
Click to expand...

The whole thing is confusing. My 0.5 micron chromium oxide gives a smoother finish under the microscope than my 0.25 micron diamond paste, so even micron size is debatable. Natural stones don't have micron ratings, even many synthetic stones don't have micron ratings. The whole thing is a confusion, so I just judge fineness by looking at the scratch patterns.

That's how they rate natural waterstones, by comparing the scratch pattern to Shapton Glasstones:
http://thejapanblade.com/test1.htm
 
cotdt said:
The whole thing is confusing. My 0.5 micron chromium oxide gives a smoother finish under the microscope than my 0.25 micron diamond paste, so even micron size is debatable. Natural stones don't have micron ratings, even many synthetic stones don't have micron ratings. The whole thing is a confusion, so I just judge fineness by looking at the scratch patterns.

That's how they rate natural waterstones, by comparing the scratch pattern to Shapton Glasstones:
http://thejapanblade.com/test1.htm
Click to expand...
Perhaps it's poor quality diamond paste? I remember reading someone buying .25micron diamond paste that didn't even abrade any material, diamond paste can vary with the amount of diamonds in it.
 
cotdt said:
The whole thing is confusing. My 0.5 micron chromium oxide gives a smoother finish under the microscope than my 0.25 micron diamond paste, so even micron size is debatable. Natural stones don't have micron ratings, even many synthetic stones don't have micron ratings. The whole thing is a confusion, so I just judge fineness by looking at the scratch patterns.
Click to expand...

Your finish is related to shape of abrasive more than size. The chromium oxide is probably leaving a finer finish because it is breaking down as you use it and the diamonds do not.
 
Roger999 said:
Perhaps it's poor quality diamond paste? I remember reading someone buying .25micron diamond paste that didn't even abrade any material, diamond paste can vary with the amount of diamonds in it.
Click to expand...

Could be, it does leave a full mirror polish and after a few strokes I could see black coloring where the paste was applied.

knifenut1013 said:
Your finish is related to shape of abrasive more than size. The chromium oxide is probably leaving a finer finish because it is breaking down as you use it and the diamonds do not.
Click to expand...

That makes sense. That also makes micron ratings not so useful, except for diamond paste.
 
Even the same size particles cut differently if they're different abrasives.

This is common knowledge in the lapidary community. You need to match the abrasive to the material and finish you desire. For example, obsidian will not polish with diamonds no matter how fine you go, while just a bit of buffing with cerium oxide brings it to a mirror shine.
 
Interesting, thank you all very much for the thoughtful comments and ideas :thumbup: I need to read up on this subject a bit more :o

While my main finishing stone is a 2 X 8 inch Spydie UF, I do have a few UF Sharpmaker replacement rods I picked up for their greater portability. I'm going to lap the heck out of one of those and see how it does.

Thanks again.
 
The micron size of the abrasive in the medium, fine, and ultra fine are all the same, IIRC 15-25 micron. It is the binders, firing, and surface finish that change the effect on the honed steel. Sal himself wont assign a grit equivalent, only to go so far as to say they are medium, fine, and fine with a surface finish. The estimations were made by others comparing scratch patterns. Yuzuha had some good photos showing the difference in how the UF abraded steel as compared to waterstones with their 'potato-chip' shaped particles. Something like SiC has acute angles that dig deeper into the steel, while I think a coticule has facets that meet at 120 degrees.

lapping the UF rod was pretty surprising, the difference felt just from skin contact was immediate. When I worked an edge with it a little, there was far less swarf on the stone surface. It still abraded well, but obviously less metal was removed.
 
The other problem is that ceramics and waterstones are just two elementally different kinds of abrasives. Waterstones have abrasive particles (of varying shapes, hardnesses and sizes, depending on what kind of waterstone) in a soft-ish matrix, while ceramics are entirely abrasives, but fused and therefore rounded and more hill-and-valley-y and less jagged peaks like some abrasives.

I think you'll find that even Sal will qualify his micron-rating, saying that it's just a rough equivalency, since there are no individual grits to measure.

EDIT: What Hardheart said (better) while I was posting.
 
You must log in or register to reply here.
Back
Top