Right sharpening stones

N

nedocervar

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Some time ago I read in BF that particular steel need particular stones to optimize sharpening work.
It's only a matter of more or less hard/soft steel or there's more to come?
I would appreciate your opinion.
Thanks in advance.
-Nedo Cervar
 
???? Well, yeah, I hear there is an art to picking the right Uchigumori or Suita stones and then the proper Jizuya and Hazuya fingerstones for Japanese sword polishing. This is a cosmetics thing though.

Arkansas stones are a bit slow but can put a really nice edge on most common knife blades (including US and German kitchen knives), but would probably be a poor choice for some of the harder steels or carbides (Novaculite stones are made of silica and have a hardness about 5.5 mohs, which would be around 59 Rockwell c,... be there all day trying to grind your M2 BM710HHS since it has a hardness of about 62Rc... some of the Japanese chef knives range up to Rc 67).

Most of your other oil stones, ceramic and water stones use harder abrasives like garnet about 7.5 mohs (Belgian stones), chrome oxide 8.5 mohs, aluminum oxide 9 mohs (same as ruby or sapphire) or silicon carbide 9.5 mohs, and are plenty hard enough for most all steels.

But yes, you will find some steels like certain stones better than others.... some stones leave a dark haze on stainless, others leave it bright and shiny. One steel may gum up one stone but not another. When you get down to polishing the edge, softer steels seem to sharpen better on harder (more tightly bonded) stones (soft steel is a bit pliable and rubbery and a hard stone seems to control the edge geometry better). And hard steels (which can form a thinner, keener edge) seem to work better on softer (more loosely bonded) stones (they wear faster exosing new grit so will cut harder steel faster, but also seem less likely to round the edge when hand tremmors make microscopic variations in the angle you are trying to hold... will simply make a microscopic gouge in a soft stone without damaging the edge too much, but a hard stone doesn't gouge easily so might blunt that keen edge you've been working on.... done that before... took my zdp-189 Cali jr. to a hard 15k Shapton polish stone and it wound up duller than it was after the 8k stone, so I had to go back to the 5k stone and be really super careful with that 15k stone.... HoB's 10k Naniwa stone is softer and would probably have been a better finishing stone for this knife... I'll have to get me one of those to add to my collection)
 
Yuzuha, many many thanks! I always learn a lot from your reply. Great BF.
Sincerely.
-Nedo cervar
 
nedocervar said:
It's only a matter of more or less hard/soft steel or there's more to come?
Click to expand...

The carbide content is often as critical as the hardness, the very high vanadium steels for example are much slower to work than steels without hard carbides but which are actually harder. There is also some evidence that the very high vanadium carbide steels finish better with diamond stones to cut the carbides than other softer stones. I am not sold on that arguement totally yet based on what I have seen.

-Cliff
 
Cubic boron nitride (CBN/Borazon) is recommended instead of diamonds for grinding steels (diamonds burn and dissolve into iron so CBN works better than diamond), but I hardly ever see it in hand or bench stones... only a few touch up tools for tungsten carbide cutters, like these http://www.titantoolsupply.com/tbhh.html

not sure why... maybe because there isn't as much of a heat problem with hand honing? CBN is also harder than things like tungsten, vanadium or silicon carbide so should not have any trouble with high carbide steels either, but I'm curious about the different handling characteristics (a diamond plate should have a different feel and cutting properties to a CBN stone)
 
Yes, wheel grinding is different than hand honing, I have about a dozen diamond hones of various shapes. I have head the carbon burn out arguement before but it doesn't seem that way in practice, they last a lot longer than waterstones for example. Though I would be interested in CBN stones if they were available.

-Cliff
 
yuzuha said:
Cubic boron nitride (CBN/Borazon) is recommended instead of diamonds for grinding steels (diamonds burn and dissolve into iron so CBN works better than diamond), but I hardly ever see it in hand or bench stones... only a few touch up tools for tungsten carbide cutters, like these http://www.titantoolsupply.com/tbhh.html

not sure why... maybe because there isn't as much of a heat problem with hand honing? CBN is also harder than things like tungsten, vanadium or silicon carbide so should not have any trouble with high carbide steels either, but I'm curious about the different handling characteristics (a diamond plate should have a different feel and cutting properties to a CBN stone)
Click to expand...

I have been involved with the jewelry business for many years. Diamonds are nearly pure carbon. I have seen jewelry grade diamonds heated to over 2000 degrees with no ill effect. In fact, they are often cast in place. Diamonds don't dissolve into iron- they may chip microscopically, but I don't believe you could dissolve one.
Bill
 
It isn't heating, but the carbon in the steel and the carbon in the diamonds, see for example "Modern Grinding Process Technology" by
Stuart C. Salmon.

"diamond, being a carbon based material, has an affinity for the carbon
in the steel and suffers accelerated wear by the dissolution of the diamond
into the carbon in steel, producing an iron carbide (Fe3C) with most
unsatisfactory results."

-Cliff
 
Thaks Cliff, Yuzuha and Bill. I recognize your knowledge. But where are the other "experts" which branded my question "ridiculous"?
I don't bear the self importance of guys that are not equal to a task.
Apologize my vent.
-Nedo Cervar
 
If you are refering to me I don't think I'm an "expert". I also don't think I called this question "ridiculous". However, your other thread I think was. To answer your question in this thread, it's my opinion all common brand sharpening stones will get a knife sharp. Some faster than others, and some with a more polished edge than others. It kind of depends on what your looking for and what you call sharp.
 
db said:
If you are refering to me I don't think I'm an "expert". I also don't think I called this question "ridiculous". However, your other thread I think was. To answer your question in this thread, it's my opinion all common brand sharpening stones will get a knife sharp. Some faster than others, and some with a more polished edge than others. It kind of depends on what your looking for and what you call sharp.
Click to expand...
IMHO not all sharpening stones will get a blade scary sharp. Fine ceramic stone is painful to finish on something like a knife as the steel is soft and the wire flip-flop here and there before it gets cut, for istance. In that case a fine diamond can serve the purpose.
Usually my first choice is an old belgian very soft waterstone with hard steel (over 60 HRC).
But i can get a good sharpening work only by sandpaper with a particular japanese knife. Don't ask me why because I don't know.
For industrial scissors, after reprofiling, nothing is better than grey ceramic for bevelling and ultra fine for deburring.
Naturally I finish the sequenze almost always stropping with leather CrO charged. But here I am false! Try the final strop on a piece of newspaper (by a special expert:D )
- Nedo
 
You can try some water and a nagura stone to make a nice "mud" on that fine ceramic as, even if it doesn't totally get rid of that burr problem, the mud will often help break up or control that burr.
 
Sounds, to me, like you've got what stones work for you. Like I said it does depend on what your looking for and call sharp. Exsample, I rarely highly polish any of my edges. The way I use most all my knives a coarser edge just works best. So for me really sharp means a medium ceramic finish, and a highly polished edge is just sharp.
Also I do not always try and get a burr when sharpening. I only work at getting a burr when regrinding the edge bevel. Right or wrong it works for me.
 
Yuzuha, I will try your advice this night, after work.
db, it seems to me you want only be an opposer, without both profit. If I misunderstand I apologize to you.
Tanks.
-Nedo
 
“db, it seems to me you want only be an opposer, without both profit. If I misunderstand I apologize to you.”
Not at all. I do have my own opinions, and use what works for me. I’m no expert and I don’t think what works for me is what works for everyone. Nor should it and I don’t try and tell others it should, or my way is the only and best way. The only reason I even posted in this thread of yours is I believed you called for me.
“Thaks Cliff, Yuzuha and Bill. I recognize your knowledge. But where are the other "experts" which branded my question "ridiculous"?”
To tell you the truth I’m too lazy and stupid to argue with you over 2 different threads. If you don’t want my opinion don’t ask for it.
 
I guess I will add my $0.02 as well. Yuzuha pretty said already all I could add to this question. I just wanted to point out that regardless of the steel you are sharpening and the hardness of the abrasive there are differences in the stones that have a bearing on the performance. Mainly uniformity in particles size but more importantly particle shape and binder can have enormous influence on the cutting ability of a certain abrasive. These are pretty difficult to quantify (there was a decent scientific study that determined that the cutting speed is largely dependent on the "polygonity" of the particle, even more so than on particle size. Particles that are a higher order polygon cut faster than lower order poygons. A round particle cuts the slowest, but a cube will cut slower than an octahedron etc. They speculated that the number of cutting surfaces increases.) and even more difficult to determine as ELU and a lot depends on you personal preference but there are definitly quality differences between the stones. So you probably have rely mostly on reputation than on hard data, but I would imagine that you would do alright with most steels on any stone of decent quality. There are, however, the exceptions that Yuzuha already mentioned. You might find that you need a soft waterstone for the highly hardned Aogami and Shirogami steels and don't do too well with a ceramic stone, just to give some extremes. The fact that some people had some problems sharpening the Caly Jr. ZDP with the Sharpmaker just underlines this argument. But I think that by adjusting the pressure, you can get very far with most steels if you have a decent quality waterstone.
 
HoB said:
... the cutting speed is largely dependent on the "polygonity" of the particle
Click to expand...

That would seem obvious as the points would raise the pressure for a given load and also maximize the chance that any given orientation presented points and not flat surfaces to the abrading media. However this is obviously a peaked behavior because a round ball is simply an infinite faceted surface.

-Cliff
 
I would assume so, as well, but the study was incomplete in that regard. It is apparently very difficult to engineer particles in that size range to have a certain shape. So you can not simply engineer a progression of polygonity from 4 to x corners but it appears that you are kind of stuck with what nature is willing to give you. However, I was a bit surprised that the polygonity (if that is really a word, but you know what I mean) is so high. I would have assumed that something like an octahedron would be ideal because the cutting surfaces don't protrude much at higher orders anymore. I would expect the coner of a cube to take out a big gauge and hence cut fast....but apparently not. Also, (unsurprisingly) the sharpness of the features seems to make a big difference but is even more difficult to quantify. Apparently, this is why diamonds cut "uncharacteristically" fast. They have a low polygonity, but seem to have very sharp features.

Ok,ok, I'll shut up now, this is really WAAAAY of topic now...sorry :o .
 
Interesting. Belgian blue and Coticule stones ought to cut like the dickins then since they're often dodecahedrons ( "0 grit" sandpaper? ^0^ http://www.yuprocks.com/glist/garnet7.html ) CBN seems rather irregular http://www.alibaba.com/catalog/10758801/Cubic_Boron_Nitride_CBN_B2_/showimg.html (similar to diamond... see diamond compounds in the middle of the page http://www.emsdiasum.com/microscopy/products/materials/polishing_supplies.aspx ) Here's an interesting page showing different aluminum oxide and silicon carbide grains and knoop hardness of various materials http://www.sabreindia.com/sabre/bonded abrasives/wheel components.htm
 
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