Super Specific Sharpening/Abrasives Questions

[nutsforknives]

These are general things I am curious about, and I figure there are a few people on here who might know the answers or have some insight for me. Some questions are super specific, regarding the various diamond and cbn stones that have recently become available, or regarding high vanadium steels.

- Why do manufacturers use CBN sometimes instead of diamond, and is there any benefit to sharpening with CBN over Diamond?

- If I want to put a low grit, like 600 grit finish on a high vanadium steel, do I have to use diamonds/CBN or is AlO/SiC ok?

- For low grit edges, what is a good way to deburr/refine a bit without losing that aggression? I am experimenting with a few stropping strokes on a spyderco UF stone, then a few on 1um diamond strop. It seems to work well on 154CM but I haven't tried it with my CPM-M4 folder yet, the one I actually need to be low grit for skinning.

- Are metallic bonded CBN stones more similar to a resin bonded stone like a venev, or a coated plate like DMT?

- Besides whittling a hair or slicing a sheet of paper, what are some tests you use to judge sharpness? For example, I fold and roll up a paper towel so I have a tight cylinder, then slice through it on a cutting board. Really tells me a lot more about how something will cut than the paper test or just feeling the edge with my fingers.

- Does anyone do a highly polished finish on high vanadium steels using diamonds, and then "expose the carbides" with a few strokes on an AlOx based abrasive, like an 8k waterstone or spyderco UF? I am experimenting with this and getting mixed results, I'm wondering if anyone has a particular technique or procedure they do that gets this effect. Trying to find that balance between maximizing performance and minimizing carbide tear out, and I'm not sure how much time I should spend on the ceramic, if I should strop a bit after... you know how it goes messing around with edge finishing.

That's probably enough super specific esoteric questions about sharpening. Hopefully the genuine experts and experienced amateurs who know the answers will see this. Thx

 

[Mr.Wizard]

- Why do manufacturers use CBN sometimes instead of diamond, and is there any benefit to sharpening with CBN over Diamond?

cBN is used to avoid thermo-chemical wear that occurs with diamond when grinding ferrous material at elevated temperatures (powered grinding). I haven't seen any well substantiated claims of superiority (over diamond) for manual stoning and filing.

- If I want to put a low grit, like 600 grit finish on a high vanadium steel, do I have to use diamonds/CBN or is AlO/SiC ok?

600 grit in which scale? Anyway there is some disagreement which you can read here: https://www.bladeforums.com/threads/finishing-grit-for-skinning-knives.1728637/page-2

- For low grit edges, what is a good way to deburr/refine a bit without losing that aggression? I am experimenting with a few stropping strokes on a spyderco UF stone, then a few on 1um diamond strop. It seems to work well on 154CM but I haven't tried it with my CPM-M4 folder yet, the one I actually need to be low grit for skinning.

I don't know if it's any better but if you want something else to try: https://www.bladeforums.com/threads/polished-on-one-side-coarse-on-the-other.1724748/

- Are metallic bonded CBN stones more similar to a resin bonded stone like a venev, or a coated plate like DMT?

In terms workpiece surface roughness it should be closer to electroplated diamond (like DMT): https://www.bladeforums.com/threads...d-type-on-finished-surface-roughness.1706791/

- Besides whittling a hair or slicing a sheet of paper, what are some tests you use to judge sharpness? For example, I fold and roll up a paper towel so I have a tight cylinder, then slice through it on a cutting board. Really tells me a lot more about how something will cut than the paper test or just feeling the edge with my fingers.

I use all of those. Also rather than slicing flat paper I like to cut a loosely rolled piece as it takes some edge aggression to bite into the side of the roll.

 

[nutsforknives]

Awesome. So many questions answered here. Thanks. Between this thread and your responses in another thread I started (initially about skinning knives), I think you have significantly contributed to my skill and knowledge with sharpening.

 

[wade7575]

N nutsforknives From what I understand CBN there 2 reason's it's used the first was answered,CBN can withstand more heat then diamond before it gets soft,from what I understand CBN has more facit's.

When it comes to steels with vanadium you do not always need diamonds to sharpen that steel,with vanadium I used to think and a lot still do that vanadium is only added so it can form vanadium carbides and that is not true,when it comes to the vanadium in the steel when it is being made must be brought up to a certain temperature and held there for the vanadium carbides to form,vanadium is also very useful in refining the grain structure of the steel so the steel has a much finer grain structure,with some steels they are not always taken to the temperature to turn the vanadium into carbides depending on how the maker wants the steel to perform and other factors are taken into account such as if they want the steel to be more tough or less tough and so on.

In reguards to to most steels with vanadium I think I read that most are taken up to the temperature to form vanadium carbides so I would safe yes to be safe if your not sure use diamonds or CBN.

I find the Metallic CBN stones to do a very good job at refining an edge if you have a fine enough Metallic CBN stone,I have a 50 80 120 400 1K 4K 8K 15K and soon a 30K,I mainly use the 120 as my lowest grit stone as it doesn't tear up the edge to badly and if I progress up to 4 and 8K the edge is somewhat refined but at the same time toothy and if stropped you can get a very good working edge out of it and if take to the 15K it's kind of like a hybrid edge that is refined and toothy and I still strop it.

What I always tell people is to get a 120 240 and 400 Metallic CBN stone and then get a 400 800 and 1200 Venev stone in 100% concentration that way the end user isn't having to invest as much into a big set of Metallic CBN stones and if they want they can still work up to that slowly.

With the Venev stones they claim the resin is not abrasive but I think it is to a certain degree and it help's to polish and refine the edge so that very little stropping is needed to refine the edge even further,if just the Metallic CBN stones are used more stropping is needed with a good quality diamond spray or emulsion like Jende or Portland Knife House,I have not tried the Portland stuff yet but 4 of my friends on Facebook groups have tried it and say it cut's faster then anything else they have tried and it gives your edge more bite and doesn't polish the edge as much.

If it were me I would go with the Metallic CBN 120 240 400 and then get the Venev 400 800 1200,the reason I suggest this is because the Metallic CBN stones will last much longer then anything else and for lower grit sharpening where edge refinement isn't so important then hop over to the Venev stones,everyone that I have told in the facebook groups I'm in to use that combo really seem to like it and the edge that the Venev give when finishing with them and that's where it's more important at the 400 grit mark to stone using stones that are going to refine the edge.

I also sometimes use water stones on steels that have vanadium carbides in them after I have used the Venev 1200 grit stone,a Venev stone is rated in FEPA-F and it converts to JIS 4K,if you use a 4 or 6K to start after the Venev 1200 and even a Suehiro G8 stone it's not going to matter to much if you are just using the stones to remove scratch's,depending on the steel result's can very and for example with S110V after you use the Venev 1200 you want to get in and out with each stone as fast as you can so to speak.

I find use the high grit water stones on S110V and some other high alloy steels as little as possible and use it just enough to remove the scratch's,S110V is a terrible steel to sharpen from start to finish even if Sic stones are used the edge will be crap and won't hold it's edge very long,the first time I tried doing a mirror polish on S110V only using Sic for lower grit and aluminum Chosera's and Suehiro's for finishing and then stropped it the apex of the edge felt very sharp to the touch but when it cut like a butter knife.

With S110V normally it hate's being polished and that's because most high grit stones are water stones that are sic and aluminum oxide but when I use the Metallic CBN stones all the way to 15K it's night and day different and S110V loves that edge in comparison to anything done with traditional water stones.

 

[Kevin fitz]

Hey, idk if this is the right place to post im new to forums. I was wondering if anyone knew what type or resin to use for making my own cbn/monocrystalline sharpening stones? I know venev uses phenolic resin but I can't seem to figure out how to even use that resin, is it heat, pressure is there a liquid version to mix up? If anyone has any insight on resins or making there own stones any advice is appreciated thank you

 

[maximus83]

- Why do manufacturers use CBN sometimes instead of diamond, and is there any benefit to sharpening with CBN over Diamond?

- For powered sharpening: because CBN is better at handling the heat of powered grinding without breaking down and leaching abrasive grit into the metal being sharpened.
- For manual sharpening: no known difference has been shown and I haven't seen any with the CBN (3 different products) and diamonds (DMT, Atoma, cheap Chinese-made) that I've used. The differences you see IMO will be more about the differences in the way a given stone/plate was manufactured, rather than whether the abrasive consists of diamonds or cbn.

- If I want to put a low grit, like 600 grit finish on a high vanadium steel, do I have to use diamonds/CBN or is AlO/SiC ok?

- You absolutely need diamonds or cbn to get the best possible edge. Because these materials can actually cut/refine the carbides in the steel, versus just tearing them out the way a coarse SiC stone does.

- For low grit edges, what is a good way to deburr/refine a bit without losing that aggression? I am experimenting with a few stropping strokes on a spyderco UF stone, then a few on 1um diamond strop. It seems to work well on 154CM but I haven't tried it with my CPM-M4 folder yet, the one I actually need to be low grit for skinning.

- That's a reasonable approach, I actually do something similar, as did Jason B., who used to be more active here. Another approach that works is a few super light strokes--barely touching the metal--on a high-grit diamond plate such as DMT EEF. If you can't get the micro burr that way, do only 1 or 2 VERY light passes at a slightly elevated angle.

- Are metallic bonded CBN stones more similar to a resin bonded stone like a venev, or a coated plate like DMT?

- Metallic generally don't shed grit. This has both pros and cons, like any other stone attribute it's a trade-off. According to what Gritomatic told me recently when I asked about his CBN stones for Edge Pro, the metallic bonded CBN he sells will require less maintenance in the short run compared to resin-bonded, because you don't flatten them in the normal way (such as using SiC powder on a glass plate). But in the long run you will still have to maintain these stones to refresh the grit, for example you can etch them with a ferric chloride solution.
- Does metallic bonded produce any difference in the finished edge, vs resin-bonded? This I can't say, as I don't have any metallic bonded stones yet, but very interested in this question which is why I'm considering getting Gritomatic's metallic bonded CBN coarse stone, for profiling.

- Besides whittling a hair or slicing a sheet of paper, what are some tests you use to judge sharpness? For example, I fold and roll up a paper towel so I have a tight cylinder, then slice through it on a cutting board. Really tells me a lot more about how something will cut than the paper test or just feeling the edge with my fingers.

- For informal testing where you're not using devices and etc, the best testing protocol I've seen and using myself is the Sharpness Chart, that Knife Grinders posts on their site, and in a sticky in this forum. The tests in there, were correlated to the width of your edge and if you can pass certain tests (such as push-cutting super fine cigarette paper), you'll know you have an edge whose width at apex is in the ballpark of what's on the chart. For informal testing, I haven't seen a better approach than this chart.

 

[HeavyHanded]

-If I want to put a low grit, like 600 grit finish on a high vanadium steel, do I have to use diamonds/CBN or is AlO/SiC ok?

At 600 I'd go with diamonds. At 400 or less I haven't seen any big difference between diamond and SiC, but AlumOx seems to have trouble at any grit. If I'm going higher than the fine side of a Crystolon stone I switch to diamonds.

- For low grit edges, what is a good way to deburr/refine a bit without losing that aggression? I am experimenting with a few stropping strokes on a spyderco UF stone, then a few on 1um diamond strop. It seems to work well on 154CM but I haven't tried it with my CPM-M4 folder yet, the one I actually need to be low grit for skinning.

The best overall method is to use a fairly low angle 26° or so with a very coarse stone or plate, then microbevel with a very fine abrasive at about 2° higher per side. The number of passes will customize the finish - a few passes = very aggressive slicing, more passes will slowly work back into the bevel and the irregularities will disappear.

You can also step up to a less coarse stone and strop with diamond or CBN, which has a similar effect. I get better life from the microbeveled edges but is not to a huge degree.

- Besides whittling a hair or slicing a sheet of paper, what are some tests you use to judge sharpness? For example, I fold and roll up a paper towel so I have a tight cylinder, then slice through it on a cutting board. Really tells me a lot more about how something will cut than the paper test or just feeling the edge with my fingers.

A sheet of newsprint cut across the grain, and then run along the face of it free-hanging to see if the edge catches. If the edge is straight I'll roll the paper a little.

- Does anyone do a highly polished finish on high vanadium steels using diamonds, and then "expose the carbides" with a few strokes on an AlOx based abrasive, like an 8k waterstone or spyderco UF? I am experimenting with this and getting mixed results, I'm wondering if anyone has a particular technique or procedure they do that gets this effect. Trying to find that balance between maximizing performance and minimizing carbide tear out, and I'm not sure how much time I should spend on the ceramic, if I should strop a bit after... you know how it goes messing around with edge finishing.

At the finishing level ALL work on super steels should be with diamond or CBN.