20 CV sharpening

[as08da09d14kljad089]

I am buying a lansky sharpener system for my knife. Should I spend the extra money for the diamond stones or will the regular stones cut fine.

 

[Jason B.]

You will need diamond stones with that steel.

 

[microtech85]

Ceramics will work. I have cpm 20cv on my benchmade 940 and m390 on my valet. I am able to get a screaming sharp edge on both with the brown spyderco ceramic. Then i do a few passes on strop loaded with green compound. So it will work. So far the only steel i have had troubles with is the s90v. But even then i can still get a very good edge but not quite as good as i get with the 20cv.

 

[Obsessed with Edges]

I am buying a lansky sharpener system for my knife. Should I spend the extra money for the diamond stones or will the regular stones cut fine.

For anything needing reprofiling or even moderate re-crisping of the edges on high-vanadium steels like that, you'll likely need diamond. And I can pretty much guarantee you'll DEFINITELY WANT diamond, after seeing how long it takes to do much grinding with the very small Lansky hones; especially the standard hones in aluminum oxide. The small size of the hones is the most limiting factor; so, you'll want and need every additional advantage you can get, in using them on such steels.

Also keep in mind, the vanadium carbides in such steels will eventually ruin the surface finish on the standard aluminum oxide hones, or on ceramics for that matter. They'll get glazed by the harder carbides in the steel, and their working speed will plummet to near-zero effectiveness. And it won't take long for that to happen.


David

 

[Mo2]

You want diamonds because ceramic won't sharpen the carbides that are harder than the surrounding steel that holds them.

So while you can get 20cv knife sharp with ceramic you won't be sharpening the carbides and they may also tear them out. And the ceramics load really fast. So they will need to be cleaned off during the process so it doesn't load when sharpening.

So yes get the diamond. SiC works well too if you can find a kit with SiC stones. Cheaper too.

 

[cbwx34]

With the tiny stones of the Lansky, get diamond, you’ll need all the help you can get.

 

[Alberta Ed]

Diamond hones will last for decades if used properly - not too much pressure, and clean them when they get loaded up.

 

[maximus83]

Diamonds, CBN, or silicon carbide are the materials you need. If you're bound determined to use a guided/jig type of system, I'd get the Spyderco Sharpmaker instead, and add any one of these 3 options: their diamond stones, their CBN stones, or the Congress Tools Moldmaster SiC triangle stones (the 1/2" size to fit Sharpmaker), get 2 each in whatever grits you want ranging from 150 to 600. I'm trying those Moldmaster stones in the SM, they are fantastic but the catch is they'll have to be lapped, and I don't know how long they'll last.

 

[microtech85]

I use my spyderco double stuff half the time to sharpen my m390 and i have no problems. To go from an edge that would jist barely shave arm hair to one that would pop hairs took 2 minutes. Diamonds sre definstely useful for cutting faster but i only use my dmt if my edge is super dull or damged. Each mis-stroke on diamond will set you back further than a mis-stroke on ceramic. I may record a quick video cutting through a paper towel with my ceramic sharpened edge. I wil do this to show that ceramic will indeed give you a great edge. As to not cutting carbides, i have no idea, i dont have a microscope, so i havent seen it with my own eyes and it doesnt seem to cause any disruptions on my edges. I can only maybe agree with the neccessity of diamond for s90v or higher. s90v has caused damage to the corners of my medium sharpmaker rods but no damge to the white.

 

[microtech85]

Here is the video i said i would make demonstrating how sharp my 20cv edge is from medium spyderco ceramic rod. Sharpness test begins at about 25 seconds in and lasts about a minute.

 

[maximus83]

Here is the video i said i would make demonstrating how sharp my 20cv edge is from medium spyderco ceramic rod. Sharpness test begins at about 25 seconds in and lasts about a minute.

Thx for vid, enjoyed watching. Have you gotten the impression that someone in the forum thinks ceramics don't work on high carbide steels? Even among the folks who don't recommend ceramics on high carbides, because of a variety of actual or potential issues, I haven't heard anybody in recent threads arguing that they don't work at all.

 

[BluntCut MetalWorks]

Thanks for sharing your video. Technically I agree, ceramic can shape/sharpen high carbide volume% steels to fairly keen/sharp level. From sound & angle of cut in your video - I guess, edges were refined to between 10-20 microns irregularities/toothiness (where apex width probably half of that). This level is plenty sharp for most users.

In sharpening-nut world, many of us enjoy thinner edges, so we sweat sharpening details... My main reason for guessing 10-20um edge irregularities (teeth apex width probably 5-8um) because your blades successful angle of slicing - ~45um thick phonebook paper - is more than 45 degrees off perpendicular to paper. So at 45* slicing angle = cutting contact length (effective paper thickness) = sqrt(45^2 + 45^2) = 63.6um. At 30* would be 100.6um, which is same thickness of std copy/printer paper. In order to push cut at 90* (blade perpendicular to) phonebook paper, edge irregularity need to be less than 5um for with/along grain and sub micron for cross grain. Similar requirement for no-tug/pull dry shave facial hairs.

Back to protracted argument on ceramic/SiC vs high VC edge. Same old - when shape edge thinner than VC diameter, we either shape VC or knock VC off the apex. Which abrasives can and which can't (knock 'em away) shape VC? Round and round we go... again.

Here is the video i said i would make demonstrating how sharp my 20cv edge is from medium spyderco ceramic rod. Sharpness test begins at about 25 seconds in and lasts about a minute.

 

[microtech85]

Thx for vid, enjoyed watching. Have you gotten the impression that someone in the forum thinks ceramics don't work on high carbide steels? Even among the folks who don't recommend ceramics on high carbides, because of a variety of actual or potential issues, I haven't heard anybody in recent threads arguing that they don't work at all.

Diamonds, CBN, or silicon carbide are the materials you need

Thanks for the compliment on the video. I am referring to the claim that i see a lot "you need diamond". I guess that can be interpreted in different ways but i interpret it to mean that ceramic and other materials will not suffice. Or perhaps it implies that the ceramics are inadequate for the steel and therefore you need diamond. In this particular quote of yours you say "the materials you need" and to me "need" implies other materials don't work. Perhaps you just meant "the materials you want". But in my video i was not referring to your post, i wast responding the the generic advice that i see regarding the need for diamond. My point of the video was simply to show that ceramics will indeed get these high end steels sharp, and pretty easily too. But i definitely did not make the video to to call anyone out.

 

[microtech85]

Thanks for sharing your video. Technically I agree, ceramic can shape/sharpen high carbide volume% steels to fairly keen/sharp level. From sound & angle of cut in your video - I guess, edges were refined to between 10-20 microns irregularities/toothiness (where apex width probably half of that). This level is plenty sharp for most users.

In sharpening-nut world, many of us enjoy thinner edges, so we sweat sharpening details... My main reason for guessing 10-20um edge irregularities (teeth apex width probably 5-8um) because your blades successful angle of slicing - ~45um thick phonebook paper - is more than 45 degrees off perpendicular to paper. So at 45* slicing angle = cutting contact length (effective paper thickness) = sqrt(45^2 + 45^2) = 63.6um. At 30* would be 100.6um, which is same thickness of std copy/printer paper. In order to push cut at 90* (blade perpendicular to) phonebook paper, edge irregularity need to be less than 5um for with/along grain and sub micron for cross grain. Similar requirement for no-tug/pull dry shave facial hairs.

Back to protracted argument on ceramic/SiC vs high VC edge. Same old - when shape edge thinner than VC diameter, we either shape VC or knock VC off the apex. Which abrasives can and which can't (knock 'em away) shape VC? Round and round we go... again.

thanks for the detail analysis. The knife will push cut the phone book paper too, i just didn't think to record it. For me personally, my favorite method for testing sharpness is how clean it will cut through paper towel. Because even the slightest burr or imperfection will catch the paper towel and tear it.

 

[maximus83]

Thanks for the compliment on the video. I am referring to the claim that i see a lot "you need diamond". I guess that can be interpreted in different ways but i interpret it to mean that ceramic and other materials will not suffice. Or perhaps it implies that the ceramics are inadequate for the steel and therefore you need diamond. In this particular quote of yours you say "the materials you need" and to me "need" implies other materials don't work. Perhaps you just meant "the materials you want". But in my video i was not referring to your post, i wast responding the the generic advice that i see regarding the need for diamond. My point of the video was simply to show that ceramics will indeed get these high end steels sharp, and pretty easily too. But i definitely did not make the video to to call anyone out.

I've used ceramics myself--recently--on high carbide steels and reported that in other threads, plus discussed in PMs with @FortyTwoBlades. So I know they work. My take is that they are not optimal for these steels, and there are better choices. I've personally worn down and glazed sharpmaker rods from excessive sharpening s30v/s35vn steels, so I've experienced this firsthand, admittedly on a small scale compared to professional sharpeners. I don't claim any advanced knowledge of it, but my experience fits with what I've seen others report on the issues with ceramics. I've also noted that if I tried to do any extensive sharpening of these HC steels on ceramic, starting with a really dull knife to begin with that needed an edge reset, it wouldn't work. It really could only work if I started with an already pretty sharp factory edge (or an edge I had reset elsewhere), and just touch-up on the ceramics. If I use the SM ceramics in that way, I agree, I can (and have) reproduced the same kinds of results you have. I'd still argue the ceramics are not the long-term abrasives and strategy you want to use to get best results. That said, I ain't gonna try to talk you out of what's working. Sharpmaker rods are very, very, VERY inexpensive for the main ones (not the diamond/cbn ones). Even if you replaced your SM rods every single year, the cost would still be a pittance and if you can keep your HC steel knives super sharp using the approach you showed in the video, it's a good thing.

 

[BluntCut MetalWorks]

me too - I slice rollup costco paper towel to detect burrs.

thanks for the detail analysis. The knife will push cut the phone book paper too, i just didn't think to record it. For me personally, my favorite method for testing sharpness is how clean it will cut through paper towel. Because even the slightest burr or imperfection will catch the paper towel and tear it.

 

[Lapedog]

I use my spyderco double stuff half the time to sharpen my m390 and i have no problems. To go from an edge that would jist barely shave arm hair to one that would pop hairs took 2 minutes. Diamonds sre definstely useful for cutting faster but i only use my dmt if my edge is super dull or damged. Each mis-stroke on diamond will set you back further than a mis-stroke on ceramic. I may record a quick video cutting through a paper towel with my ceramic sharpened edge. I wil do this to show that ceramic will indeed give you a great edge. As to not cutting carbides, i have no idea, i dont have a microscope, so i havent seen it with my own eyes and it doesnt seem to cause any disruptions on my edges. I can only maybe agree with the neccessity of diamond for s90v or higher. s90v has caused damage to the corners of my medium sharpmaker rods but no damge to the white.

Honestly I find ceramics fine for touching up an already decent edge on these steels. For any real sharpening or reprofiling you need diamond.

Plus I do believe it is true that the vanadium carbides are damaging the ceramic stones.

 

[microtech85]

me too - I slice rollup costco paper towel to detect burrs.

haha, yup, i use the costco paper towels too. Excellent quick and easy test. it is said that great minds think alike!

 

[microtech85]

I've used ceramics myself--recently--on high carbide steels and reported that in other threads, plus discussed in PMs with @FortyTwoBlades. So I know they work. My take is that they are not optimal for these steels, and there are better choices. I've personally worn down and glazed sharpmaker rods from excessive sharpening s30v/s35vn steels, so I've experienced this firsthand, admittedly on a small scale compared to professional sharpeners. I don't claim any advanced knowledge of it, but my experience fits with what I've seen others report on the issues with ceramics. I've also noted that if I tried to do any extensive sharpening of these HC steels on ceramic, starting with a really dull knife to begin with that needed an edge reset, it wouldn't work. It really could only work if I started with an already pretty sharp factory edge (or an edge I had reset elsewhere), and just touch-up on the ceramics. If I use the SM ceramics in that way, I agree, I can (and have) reproduced the same kinds of results you have. I'd still argue the ceramics are not the long-term abrasives and strategy you want to use to get best results. That said, I ain't gonna try to talk you out of what's working. Sharpmaker rods are very, very, VERY inexpensive for the main ones (not the diamond/cbn ones). Even if you replaced your SM rods every single year, the cost would still be a pittance and if you can keep your HC steel knives super sharp using the approach you showed in the video, it's a good thing.

I completely agree with you that for re-profiling and for sharpening very dull edges, diamond stones are a very worthwhile luxury, especially if that is how one regularly maintains their blade. But i still must disagree on the not optimal part. After doing 1050 cuts through 3/8" sisal rope until my knife could no longer slice printer paper, i was able to get my spyderco sage 3 back to easy arm hair shaving sharp in less than 4 minutes by using the brown (medium) side of the spyderco doublestuff. I made videos of these cutting tests that you can view on my channel if you would like. So to me, these are the questions. If the question is will quality ceramics sharpen a 20cv type steel to a razor's edge from not cutting printer paper and do it in less than 5 minutes, then the answer is most definitely yes. If the question is, what will cut steel faster, then it is most definitely diamond. I guess the next question could then become, if the ceramic can do it in less than 5 minutes, how fast can the diamond do it? And then, is it worth the cost difference? If the question is will ceramics be ideal for bringing back a severely damaged edge or re-profiling an edge, then the answer would be no, and if you do have to use ceramics, then it will take a long time. Again, this is just from my experience so i am not discounting your experiences. I have indeed had the corners of my spyderco medium rods wear out after about a year of sharpening s90v, but the whites don't show any wear.

 

[maximus83]

This thread is an interesting read on the use of ceramics with high carbide steels. There is NOT a consensus on ceramics, that's for sure. But a lot of interesting background and pro/con reasoning throughout, you definitely come out of it more informed on the issues, even if it doesn't change your mind. My post here summarized key arguments around the issues of using ceramics, on both sides of the issue. Probably won't change anyone's mind, but worth a read. My own view my usage: they work fine for all non-HC steels, though even there, ceramics have some issues such as loading and etc., and I find this annoying so I really quit using them for primary sharpening altogether. The ONLY primary sharpening task anymore I use ceramics for is sharpening serrated kitchen knives, and that has nothing to do with ceramics, it's just because it's so doggone slick and easy on the Sharpmaker stones. As for HC steels, IMHO ceramics are best reserved for kind of a niche role as I posted in that thread, a few very light strokes after apexing for edge refinement. I rarely even bother with that on my utility blades, but ironically I had just used my UF rods to crisp an apex earlier today, so it works for sure and I do still do that. But I won't use them for primary sharpening of HC steels, at all. Nor even for maintenance of the edges either, for that I go to a strop with diamond compound. But for sure--if your setup is working for you and keeps your cost under control--keep doing that.