Diamond sharpening and Crbides

nozh2002 said:
No, I dont, have problem as I understand, this is just theory I heard on Russian Forum - like diamonds may rip out carbides instead of sharpening them. I don't think so myself, but it will be good to have some proofe - like there is no holes in edge - marks of ripped of carbides. Cliff very well explain this - so it may happen on weak matrix.

Did you see something like this in your microskope or it is impossible to recognize carbides from matrix (I bet they are same color).

Thanks, Vassili.
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I'm no expert, but this makes sense to me. Since diamonds are so much harder then steel or carbide, it's like raking a butterknife over a chocolate chip cookie. The cookie crumbles and leaves a relatively smooth surface, but the chips get snagged and ripped out. IMHO this is why I prefer stones to diamonds. A wet stone, or even an Arkansas sloughs off some of it's surface rather then aggresively tearing into the surface of the steel. I can use a higher grit stone (as compared to a diamond) and get a more refined edge. I know we have the whole micro serration debate going on in other threads, but Vassili's comment makes sense to me. If I get micro serrations with a stone, they tend to hold an edge better than if I do it with a diamond. What do you guys think about this?
 
I don't buy it. The diamond sharpeners work. After swiping a dulled blade on a diamond sharpener just a few times the blades cut again. So what are we to conclude from that? That the matrix is doing all the great cutting and not the carbides in the steel? It doesn't make sense. I think that some of the carborundum and other abrasives used to make man made sharpening stones are also hard enough to qualify as harder than the blade and/or the carbides so there is something here I'm not seeing.

In the end all that should really matter is if the sharpener works to create a cutting edge for you or not. If it didn't work people wouldn't use them. Next hunting season in the deer camp I'd like to see someone come in and try to take all the diamond sharpeners for touch up from the guys and try to convince them they aren't needed or right to use or that they don't work. That would get you strung up on the deer pole fast. :D

STR
 
I also think that it is wrong. At least all my sharpening experience today (which I don't have that time) shows that diamond sharpening (powder on leather) perfectly work and diamond actualy sharpen carbides.

All this happen when I tryed to sharpen CPM S90V which has 15% carbides and 9% of them Vanadium Carbides which are harder then Ceramic sharpenesr. I found no progress after sharpening with Spyderco Fine - sharpness was same as after Medium. But when I got to the diamond powder on leather base (Phil Willson who HT blade recommend me to use Silicon Carbides or diamond abrasives) - I saw good increase in sharpness.

So my conclusion is that diamond actually cut carbides and make them sharp. I can imagincase when steel matrix is too week to stand force needed to cut Carbide by diamond so it fell out instead, I can imagine this happen sometimes with some experimantal bulat (wootz) made from mix of nailes and drill bits - in Russia many bladesmithes doing it in a search for true bulat (wootz) there Carbid are all in dendric structures and may be sometimes steel matrix is softer then in the homogenius steel becouse all Carbon migrated. But for CPM S90V and other productional steel it is OK I think - at least I have no problem sharpening them.

However russian experimantal bulat blades from my collection do not have any problem with sharpening by diamonds. So this is just speculations when such thing may happen hypothetically in edge cases during experimental production.

Thanks, Vassili.
 
STR said:
I don't buy it. The diamond sharpeners work. After swiping a dulled blade on a diamond sharpener just a few times the blades cut again. So what are we to conclude from that? That the matrix is doing all the great cutting and not the carbides in the steel? It doesn't make sense. I think that some of the carborundum and other abrasives used to make man made sharpening stones are also hard enough to qualify as harder than the blade and/or the carbides so there is something here I'm not seeing.

In the end all that should really matter is if the sharpener works to create a cutting edge for you or not. If it didn't work people wouldn't use them. Next hunting season in the deer camp I'd like to see someone come in and try to take all the diamond sharpeners for touch up from the guys and try to convince them they aren't needed or right to use or that they don't work. That would get you strung up on the deer pole fast. :D

STR
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I don't think that the hardness of the cutting material is the end all of the discussion. If the diamonds are bonded to a steel plate and don't come off, they will cut much differently then carborundum suspended in a stone that will come out and wear away. If I suspend diamonds in playdoh, they won't sharpen a knife, but a rock from my back yard that is not nearly as hard as those diamonds will put on a servicable edge.
 
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This is not my point. I'm not trying to find an end all to the discussion but just pointing out that in my opinion the diamond sharpeners I've used from DMT and EZELap work just fine. I think the diamonds do come out though as the sharpener wears. On some of the cheapy ones they seem to come out much faster. At least that has been the case for me but one of my favorite sharpeners is a very old well used EZE Lap diamond that is super super fine now. It does a better job for a final edge touch up than any ceramic I've ever used. I have a 1200 grit ceramic I bought from Edge Pro and it can't touch what I feel I get with this old diamond sharpener in the way of results.

STR
 
STR said:
It doesn't make sense. I think that some of the carborundum and other abrasives used to make man made sharpening stones are also hard enough to qualify as harder than the blade and/or the carbides so there is something here I'm not seeing.
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You need more than the abrasive to be harder than the carbides, the matrix has to be strong enough to withstand the force of the abrasive on the carbide as the abrasive cuts through it. Imagine for example holding a banana in your hand and someone doing a chop, you would easily hold onto the banada as the blade cut through it. Not imagine trying it with a hardwood dowel. It would be obvious that it is possible for the blade to knock the dowel (carbide) out of your hand (steel) even though the blade is much harder than the dowel because your hand isn't strong enough to withstand the contact force between the blade and the dowel.

This being said, I belive the sharpeners will cut the carbides as I have seen large increases in edge retention with steels like S30V in slicing at the same hardness of other steels and I assume the carbides are the cause as what else is there. You could argue maybe that the rough edge left by the carbides being torn out is inducing a sawing effect, but if this was the case the rate of wear on the edge would be dramatic and I don't see that either, the lower alloy steels will visibly wear faster, as an extreme example you can wear a visible notch in them cutting carpet for example.

QUOTE=nozh2002]All this happen when I tryed to sharpen CPM S90V which has 15% carbides and 9% of them Vanadium Carbides which are harder then Ceramic sharpenesr. I found no progress after sharpening with Spyderco Fine - sharpness was same as after Medium. But when I got to the diamond powder on leather base (Phil Willson who HT blade recommend me to use Silicon Carbides or diamond abrasives) - I saw good increase in sharpness.[/QUOTE]

With CPM-10V I saw no dramatic difference for sharpmaker vs diamond in terms of increase in edge retention outside of the obvious influence of change in grit. As well when I tried improving the finish of 1200 DMT with 0.5 micron chromium/aluminum oxide the sharpness increased significantly however I have not compared that to 0.5 micron diamond. Steve Elliott has also found at really high finishes, that not all abrasives are the same and that diamond finishes give superior sharpness at the same grit to chromium/aluminum oxide :

http://cablespeed.com/~sgelliott/blade_testing/html/initial_sharpness.html

It should be noted that even though he is seeing lower results for the softer abrasives, even at that level the vast majority of people would consider them extremely sharp, we are not talking about no shaving ability and blades not slicing paper.

-Cliff
 
Excellent thread, Nosh2002!

If you ever see pictures of the diamonds used to abrade steel, they look too rounded to spear carbides out of the martensite matrix.
 
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