Mirror edges

Whatever- you guys have it covered without my input.
BTW when you sharpen knives there is always loss of blade height (edge to spine.) How do you think knife blades wear out?
 
Bill DeShivs said:
Whatever- you guys have it covered without my input.
BTW when you sharpen knives there is always loss of blade height (edge to spine.) How do you think knife blades wear out?
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While true it is minimal and insignificant. I don't raise a burr until I I'm on a 7.35 micron stone--ostensibly my burr is only 7.35 microns. Many people raise burrs on 50+ micron grit diamond stones, so I feel I'm actually being very conservative with my blade steel. The only knives I've seen that are worn out were sharpened over much on too coarse of stones or they were sharpened over much on power wheels. What I was saying earlier was that putting a mirror finish on the bevels doesn't remove steel in the edge to spine dimension--one is only polishing the sides. Sharpening a knife is a different matter.

I was also genuinely asking for your input on the grit size of the ruby bench stone. If they provide a sub micron finish (e.g. 0.92 or 0.5 microns) then I'd be interested, as they are cheaper than a comparable synthetic waterstone from Chosera or Shapton.

Unfortunately, saying that you sharpen gravers with these type of stones is not a sufficient amount of information for me to make a determination of the usefulness of the stones that you have suggested. Sub micron diamond and CBN sprays can be had for reasonable prices, and DMT makes a set of 6/3/1 micron diamond pastes for under $30 shipped for all three.
 
Bill DeShivs said:
Whatever- you guys have it covered without my input.
BTW when you sharpen knives there is always loss of blade height (edge to spine.) How do you think knife blades wear out?
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I sharpen most my knives daily (more like a 8000 grit hone) and my yanagi has lost less than 0.5 mm in over 2-3 years, im not worried.

I read about who sharpen with 100-1000 stones daily, THAT id nevet do.
 
Bill DeShivs said:
I'm quite sure I understand sharpening. I have been doing it for 45 years.
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While I'm not questioning your ability to sharpen - and I in fact have quite a bit of respect for you for having sharpened for far longer than I've been alive - I am questioning your understanding of the current tools available to polish and/or sharpen a knife.

Prior to your mentioning of ruby bench stones, I hadn't even thought of them as an option. Now that you have mentioned them, I'm curious to compare them to the stones that are much more commonly used by waterstone sharpeners. The base material (carborundum or ruby) should be chemically pretty much the same thing, and from my brief investigation, both synthetic waterstones and ruby stones use sintered ceramics (e.g. aluminum oxide) but the binder is likely much different between the two.
 
Cynic2701 said:
While I'm not questioning your ability to sharpen - and I in fact have quite a bit of respect for you for having sharpened for far longer than I've been alive - I am questioning your understanding of the current tools available to polish and/or sharpen a knife.

Prior to your mentioning of ruby bench stones, I hadn't even thought of them as an option. Now that you have mentioned them, I'm curious to compare them to the stones that are much more commonly used by waterstone sharpeners. The base material (carborundum or ruby) should be chemically pretty much the same thing, and from my brief investigation, both synthetic waterstones and ruby stones use sintered ceramics (e.g. aluminum oxide) but the binder is likely much different between the two.
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I went and looked em up , the only ones that I could find with a "grit" rating were rated from 80-325 "grit" no rating standard given.... So coarse on any given scale..
And they are too soft for powdered steels anyways. Even if you could get them fine enough they wouldn't be able to cut the carbides in many modern steels. On the coarse side this isn't a huge issue.....
 
I wish I could afford all the nice stones and strops some of you guys have .I have to resort to the old no money trick a piece of denim a scrap of 2x4 and mothers mag polish I easily get mirrored edges in just a few strokes . I saw it on a Rockstead knives video and it Shure works wonders on my knives .
 
Sadden said:
I went and looked em up , the only ones that I could find with a "grit" rating were rated from 80-325 "grit" no rating standard given.... So coarse on any given scale..
And they are too soft for powdered steels anyways. Even if you could get them fine enough they wouldn't be able to cut the carbides in many modern steels. On the coarse side this isn't a huge issue.....
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There is more than one type of carbide in powder steels depending on the mix and its only when the heat treat is really good that standard stones start to have troubles. I've sharpened S30V with a Norton India stone and I've had some S30V that was hardly scratched by my best waterstone and could only be done on diamonds.
 
jeffbear22 said:
I wish I could afford all the nice stones and strops some of you guys have .I have to resort to the old no money trick a piece of denim a scrap of 2x4 and mothers mag polish I easily get mirrored edges in just a few strokes . I saw it on a Rockstead knives video and it Shure works wonders on my knives .
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If you're worried about cost, here's what I have - DLT two sided strop (not the paddle, it came with black, green, and white compounds). Cost me about $30.

I've since picked up the Shun #1000/6000 combination stone from a local store for about $70.

From a factory edge, I take it to the 1000 until the scratches are uniform. Then to the 6000 for the same thing. Finish on bark river white compound. I get near mirror edges, which is more than enough for me.

I have an older Lanksy system if I really messed up a blade doing something stupid with it.

My total investment is about $100-150. Good set ups don't need to cost an arm and a leg.
 
knifenut1013 said:
There is more than one type of carbide in powder steels depending on the mix and its only when the heat treat is really good that standard stones start to have troubles. I've sharpened S30V with a Norton India stone and I've had some S30V that was hardly scratched by my best waterstone and could only be done on diamonds.
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Another thing that I'm curious about but will need to do some testing - if the stone is physically hard enough, couldn't a bit of pressure fracture the carbide and result in some "sharpening" even if it isn't as high on the Moh's scale? I realize it wouldn't polish it and would be relatively uncontrolled, but could certainly have a positive effect anyway. Would like to pick up some etchant and see what is really going on under the microscope.
 
knifenut1013 said:
There is more than one type of carbide in powder steels depending on the mix and its only when the heat treat is really good that standard stones start to have troubles. I've sharpened S30V with a Norton India stone and I've had some S30V that was hardly scratched by my best waterstone and could only be done on diamonds.
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I would agree about the carbides , Vanadium Carbide seems to be the one that many people get hung up on. Im not a metallurgist though.

I would also agree , in my posts here I've been saying "many" or "most" powdered steels , that one just got missed. But in this thread pertaining to a mirror polish I don't think you would have gotten a mirror polish on a Norton stone?

Something that I don't think has really been discussed is the grain structure of the steel having an impact on a mirror polish. The more finely grained the steel is , or the finer the carbide particles the easier it is to sharpen , and in turn mirror polish.
 
HeavyHanded said:
Another thing that I'm curious about but will need to do some testing - if the stone is physically hard enough, couldn't a bit of pressure fracture the carbide and result in some "sharpening" even if it isn't as high on the Moh's scale? I realize it wouldn't polish it and would be relatively uncontrolled, but could certainly have a positive effect anyway. Would like to pick up some etchant and see what is really going on under the microscope.
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That would come down to the Friability of the carbides in the steel , for this to work you would probably at a guess need pressures beyond what we can produce while sharpening. And I would hazard a guess to say that the pressure needed would exceed the surrounding matrixs' ability to hold onto the carbide. Purely speculation on my part. Again I cant claim to be metallurgist.

What type of scope do you have?
 
Sadden said:
That would come down to the Friability of the carbides in the steel , for this to work you would probably at a guess need pressures beyond what we can produce while sharpening. And I would hazard a guess to say that the pressure needed would exceed the surrounding matrixs' ability to hold onto the carbide. Purely speculation on my part. Again I cant claim to be metallurgist.

What type of scope do you have?
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Its hard to say, I can't find any friability index #s for Vanadium carbides. SiC can be broken down by fairly light pressure against steel -happens every time one sharpens a knife on a vitreous SiC stone. I imagine vanadium carbides are a lot less friable, but that's just a guess - some vanadium alloying materials that I could get #s for are in the range of silicon carbide. Have also come across references to VC falling in a range from 9 - 9.6 Mohs. The low end is within reach of a sintered ruby stone, the high end not so much. Too many questions.

I have access to a metallurgical microscope (Amscope) that can go to 1000x cleanly and 1600x by virtue of stronger ocular lenses, so larger image, but not much more detail. Traditionally the sample needs to be polished to a high degree before the etchant will reveal clear demarcation lines between the steel and any carbides, so not sure what might be visible at even a reasonably fine polish. Any grind marks larger than about .2u would be visible and maybe make it impossible to tell what's going on. Or maybe for our purposes it would work fine, we're not trying to determine size and content, just shape relative to the surrounding metal following several grinding methods....
 
I've read this thread and learned a lot, thanks to all for your knowledge and experience. Just don't count out the old dog (Bill) sleeping on the porch. My uncle always said, " a new broom always sweeps clean, but an old broom knows where to go". Think about it.
 
Very informative and interesting thread to read.

Someone mentioned how different steels and carbide structure affects how easily it is to polish them. I've been able to put a decent mirror edge on a zdp189 Endura by just using the Lansky Diamond with the extra fine diamond stone (purple), ceramic stone (yellow), and leather strop. This same method has gotten a mirror edge on a Benchmade 710 in D2, but I've failed at getting the same results on O1.
 
My ruby stone is finer than my finest ceramic. It is the finest one they offer. Graver sharpening requires an absolute mirror finish. I sharpen high carbon, cobalt and carbide gravers. The only thing that will make a brighter cut is solid (not powdered) diamond. Think of a big, flat, solid synthetic ruby.
I'm not sure how the abrasiveness can be measured as there is no "grit." I believe the surface finish is actually what does the cutting. Ruby is corundum. Carborundom is a name brand of abrasive.
I stay pretty current on most things cutlery related, being a knife designer and all. I have diamond, alox, sc, Arkansas, India, waterstones. I have ultra fine diamond hones, and they are very coarse compared to the ruby stone. Ceramic, hard Arkansas- none are as fine.
 
These stones are not what I would call current I see discussion of them on other forums dating back 8+ years. I also see some well respected stones experts commenting on its the same stuff that you find in good waterstones.

Carborundum is a funny sounding word for the material better known as Silicon Carbide.

Corundum is aluminum oxide, same as the ruby stones.

These two materials make up most every sharpening stone on the market today and for the past 120 years.

If they work so well then they would be widely used so my guess is they work best at sharpening gravers and not knives.
 
Mine is 30 years old. Because it's not "current" doesn't mean it doesn't work. After 30+ years of use there is no visible wear on the stone, and it works VERY well. Try that with waterstones!
Probably the reason they aren't widely used is bacause they were extremely expensive years ago, before it was common to spend big money on sharpening stones.

"Degussit Ruby Bench Stones are ideal for sharpening tools and gravers – even carbide. May be used dry or with Gesswein Stoning Oil. The pure, sintered crystals of synthetic ruby have an outstanding resistance to wear, which makes them more economical than other stones. They will not groove even after years of use. In addition to metals, they may be used on other materials such as glass, porcelain and quartz.

Ideal for sharpening knives and gravers made of high speed steel or carbide."

" Gesswein Ruby Stones are used to hone carbide and cut the hardest steels. Use these dry or with honing oil to grind, touch up or deburr steel and carbide parts. Gesswein Stones are made from pure sintered crystals of synthetic ruby. No bonding material is used, therefore, these stones are resistant to changes in shape and are extremely hard. Gesswein Ruby Stones are also recommended for used with glass quartz and porcelain. They have outsanding resistance to wear, leave very little grit on a sharpened blade, and are more economical to use that other comparable tools."

"These fine grinding stones are made of Degussit DD57 (sintered ruby) which is a homogenous mixed-crystal material. The main element is aluminum oxide. The characteristic red colour is the result of an admixture of chromium oxide.

Because Degussit DD57 is a homogenous ceramic material which is bondfree, these stones cannot be classified in terms of "grit" but only in terms of the average grain size. The average grain size of types "fine" and "medium" is about 10µ. Type "coarse" has two average grain sizes at about 10µ and 100µ.

No bonding material is used, so these stones and files are extremely hard and resistant to changes in shape. This is particularly important for quality precision grinding and finishing."
These are quotes from various sites about the ruby stone.
 
Bill, can we see some pictures of the edges finished on the ruby stone? I'm always curious to see something new when it comes to sharpening, and ruby stones are new to me :)
 
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