Where diamond leaves off and waterstone picks up....??

[hardheart]

and the fact that one abrasive is harder with sharper corners and the other soft and rounder makes no difference if the same size ? they will cut the steel the same ?

No, they don't cut steel the same.

 

[stitchawl]

and the fact that one abrasive is harder with sharper corners and the other soft and rounder makes no difference if the same size ? they will cut the steel the same ?

I haven't seen anyone say that they cut the same. Obviously some will cut faster than others.

What keeps getting repeated is that a 0.5 micron diamond compound will result in a 0.5 micron finish, just as will a 0.5 micron Cr2O3. One may cut faster or slower, but the results are going to be a finish at 0.5 micron, and the any visible difference can be seen ONLY with very high power magnification.


Stitchawl

 

[pwet]

when i say they don't cut the same i don't talk about speed, i talk about how deep the scratches produced are. i highly doubt diamonds and CrO at the same size will leave the same finish.

 

[stitchawl]

when i say they don't cut the same i don't talk about speed, i talk about how deep the scratches produced are. i highly doubt diamonds and CrO at the same size will leave the same finish.

If they are both 0.5 microns in size, they will both leave scratches that are roughly 0.5 microns. This will change when a pound of feathers stops weighing the same as a pound of potatoes.


Stitchawl

 

[Jason B.]

So why does 0.5 diamond leave a different feeling edge than 0.5 chromium oxide? I guess using them on different steels makes no difference either?

 

[pwet]

no, sorry.
first if both abrasives are 0,5 micron they wont leave scratches that are 0,5 micron at all unless you think the abrasives "enters" completely in the steel.

then i don't know how to explain this clearly in english but i'm pretty sure that something hard and sharp will scratch a material deeper than something rounder and more friable when you rub it into something. this basic concept doesn't magically change when applied to sharpening.
if so i'd like someone to explain me.

 

[Any Cal.]

While it would seem theoretical, I would expect abrasives of a certain size to leave a scratch pattern with a similiar spacing, but different abrasives to leave scratches of a different shape.

I would also expect harder abrasives (diamonds) to leave deeper scratches, which seems to be born out by the sharpening speed of different mediums. My cheap Norton stone won't touch hard s30v, even when it leaves a scratch pattern spaced similiarly to a diamond stone that cuts it quickly.

It is one reason that I would really like to experiment with using another medium to finish work done on diamonds, even if both mediums are the same grit. I would expect the softer medium to remove deeper scratches for a more refined edge at a similiar grit.

 

[stitchawl]

While it would seem theoretical, I would expect abrasives of a certain size to leave a scratch pattern with a similiar spacing, but different abrasives to leave scratches of a different shape.

Yes, I'd certainly agree with that.

I would also expect harder abrasives (diamonds) to leave deeper scratches,

This is where we part company on the issue. Assuming we are talking about diamond vs Cr2O3, both at 0.5 mics, they both are able to cut metal. They will both cut metal at 0.5 micron as that is their size. Diamond will cut it faster, but still at 0.5 micron resulting finish, just as the Cr2O3.

Stitchawl

 

[wongKI]

I'd be inclined to think that the abrasive particles wear as they cut steel even as steel itself wears as it cuts softer stuff-thus cutting less deep depending on how hard they are.

After all it's well documented that waterstones wear when sharpening steel; diamonds wear less (perhaps not at all? ) In the same way, steel of different hardness wears at different speed when cutting stuff. A 4in blade at 64 HRC will cut as deep as an identical blade at 50 HRC, but if the cut is repeated over and over again, the 50 Rc blade will wear faster and cut less deep (especially if the material being cut is wear-resistant or hard)

This should account for knifenut's experiences.

 

[pwet]

While it would seem theoretical, I would expect abrasives of a certain size to leave a scratch pattern with a similiar spacing, but different abrasives to leave scratches of a different shape.

here lies the problem. have you ever seen microscope shots of an edge ?

a scratch pattern is determined by how deep the abrasive cut not by how far from each other the scratches are because there is no space between scratches no matter the grit size.

 

[stitchawl]

a scratch pattern is determined by how deep the abrasive cut not by how far from each other the scratches are because there is no space between scratches no matter the grit size.

And that is determined by the grit size.


Stitchawl

 

[pwet]

if you want.

 

[Broos]

The DMT stones go up to 3 microns, which they call 8k grit, but 3 microns is more like 5k. So with waterstones, it would take over at 8k. You could also go onto 2 micron diamond paste, or lapping film.

I've found the Shapton Pros to work well with all steels, as does the DMTs. Some stones would just skate over stainless steels.

It takes a while (thank goodness the knife has a very thin edge), but my shapton pros will even get my cpm-10V sharp.

 

[Broos]

Grit size, density, pressure (force), and velocity will determine the rate of metal removal and finish when you are comparing them with a defined substrate and/or matrix. But comparing grit size with no reference to other factors can be confusing.

My loaded strop with 10 micron diamonds cuts very aggressively (for a strop), yet leaves a mirror finish. My 9 micron diamond plate leaves sctratches that look like the grand canyon, & cuts very aggressively (for a stone). The grit size takes a back seat to other factors in this comparison.

 

[guyfalks]

Diamond is an FCC crystal. Aluminum oxide and chrome oxide are HCP. Since they have different crystal structures, they should have different shapes and cut somewhat differently, like knives with different edge geometries.

Grit size is only approximate. Norton grade #1 (14000) paste is listed as 0 to 2 microns. I would expect the other brands & materials to vary also. I do not know how the particle sizes are determined, but I doubt it is by direct measurement. This means the particles of a given size may not actually be uniform little spheres, squares, etc. but particles with similar ratios of volume to surface area, etc.

 

[Any Cal.]

pwet, I was with you right up until you disagreed with me...

stitchawl, you're wrong too... J/K

I am having fun reading the thread, but I think that Broos may have a good point, as well as guyfalks, in that this is more than likely much like defining ultimate sharpness. With the multitude of variables, it would be very difficult to determine whether grit size, quality, hardness or lack thereof, substrate, blade steel, or something else could be singled out as to the result.

If CrO2 did indeed leave a knife sharper than .5 diamond, would that be because it broke down in use, because it was used on a different substrate, because of a technique difference in use, becuase of easier/tighter grading of the medium, or because of its shape?

 

[stitchawl]

stitchawl, you're wrong too... J/K

Damn! That's the second time this year! I'll try harder in the future!

If CrO2 did indeed leave a knife sharper than .5 diamond, would that be because it broke down in use, because it was used on a different substrate, because of a technique difference in use, becuase of easier/tighter grading of the medium, or because of its shape?

That's probably a more accurate assessment of the situation. It's also why, when I want a perfect finish to an edge, will make the last action stropping on high quality horsehide.


Stitchawl