CPM steels

[cwillett]

I’m thinking about upgrading my EDC knife to something with a modern powdered steel. Something like 3v, M390, magnacut, etc. It seems these have great edge retention, but are also “hard to sharpen”. I use Shapton glass for my kitchen knives (white, blue 2) and am comfortable with them. My EDC knives are either D2 or 1095 and I can re sharpen them easily.

Is something like Magnacut really that much harder to sharpen than something like D2? Would it just free me up from touching up my knives frequently? Or is it really a big upgrade?

[Kekoa]

This is hard to answer as opinions vary, and the ease of sharpening also depends on the geometry as well as steel. I don't personally own a PM steel so can't give an opinion on how they seem to differ in my own experience, but I can tell you that your stones are capable of sharpening modern PM steels. Basically higher wear resistance steels tend to be easier to sharpen with diamonds or CBN because they remove material faster, and the faster you remove material, the less angle discipline you need to achieve a good edge. Whetstones will remove material noticeably slower than diamonds on a high hardness, high wear resistant steel such as s90v, so you will need more angle control, but you still will be able to sharpen properly. Kitchen knives that are very thin behind the edge are easier to sharpen even in PM steels than many pocket knives or outdoor fixed blades because they have very narrow bevels, so you don't have to remove as much material to apex your edge, so getting a PM steel for a pocket knife would be more of a concern than a kitchen knife would.

In the end it all depends on the particular knife, steel, and your personal preference. It may be difficult to really know without going ahead and trying it out yourself. There may be others here as well who have more experience than me with PM steels. Just a couple extra notes though, Magna Cut and Cru Wear are a couple steels that are considered to have an improvement in edge retention but are still regarded as having nice sharpening response. Also a good technique for sharpening a new PM steel without significant extra sharpening investment might be to buy a coarse diamond plate just to apex your edge with, then your whetstones will do a good job for farther refinement. I think that would give you good results with minimal extra investment.

[Ourorboros]

The issue isn't being PM but having a lot of Vanadium. These steels are wear resistant.
You'll need diamonds for M390 and Magnacut. They will make life easier for the 3V.

[Lloyd Harner]

didnt think there was much V in magnacut. i like diamond hones for most any steel cause of the speed they cut/hone steel. 3V is not to bad to sharpen on other stones. im not sure how hard peoeple are running M390. i know 204P at 59rc is not bad at all but really not the edge holder i was hopping for. that said my last EDC was M4 at 62rc its worth the cost to pick up a diafold sharpener from DMT just to keep around and have to a back pack. they can be had in 600/1200 grit that will take care of most any EDC you might end up with

[cwillett]

Specifically, I have Shapton 500 and 2000 glass stones and an Atoma diamond plate (80?). These plus loaded strops make sharpening D2 easy. Would these be sufficient for magnacut or M390?

[taz575]

I rough in my bevels after grinding with a 120 and 220 ceramic belt, slow speed and usually a wet belt. Then I use a Shapton Glass 320, Bester 1200, Rika 5K on every knife I have and have made. I use a 1000 and 5000 diamond paste on leather strops after the stones since last January(cbn strops before that). Shaves hair, cuts receipt paper effortlessly. I use coarser strops than most since I want some bite to the edge. A 1k/5k diamond strop is awesome! They will take out micro chips on most Japanese knives, too. I do have some 40 micron/320 grit and some 1 micron diamond pastes to try on strops when I make my next one.

You do not need diamond stones for magnacut. They work faster, but good waterstones work very well on Magnacut in my experience. S90v, the diamonds really helped and worked quicker, especially with the 18" long blade Shechitas I have made. The faster you sharpen, the less error you introduce, so if you dont have good muscle memory, diamond stones can help you with sharpening by being faster and reducing error. But they also remove material faster, so you can screw up worse.

I've brought back a 62 hrc aebl blade with a visible flat edge bevel back to sharp with my diamond strops in less than 5 minutes. They just work fast on anything, period.

Every knife, every steel I use get those 3 waterstones. 52100, white, blue, aogami super, R2, M390/CPM 20CV at 60, O-1, D2, 1095, Elmax at 62 Hrc, Magnacut at 64, CPM CruWear at 60, s90V at 61, Nitro V and AEBL at 62 HRC, CPM S30V, S35VN, CPM 154, 80CRV2, 8670, CPM 3V, etc.

You do not need to spend money on diamond stones for Magnacut. Diamond strops, however, are great for touch ups and up keep, but Magnacut holds an edge a long time. Not quite as long as s90V or m390, but close and its easier to sharpen.

The glass stones you have will work fine on Magnacut or m390. Get some diamond pastes for some strops for the finer grits, much less expensive than the diamond stones! If you want, drop me a PM and I can go over more info with you.

[ex1580]

My every day pocket knife is made of Maxamet steel. I use Atoma diamond plates to sharpen it and strops loaded with diamonds to finish it. It's crazy sharp and stays that way for a very long time. I do it this way mostly because it would take approximately forever with anything less than diamonds. As long as the steel you choose isn't too extreme (let's say less than 3% Vanadium) I would try to sharpen it on whatever stones you already have and just finish it on some diamond loaded strops. If it has more Vanadium than that you may find it takes a while. If you don't have that kind of time then buy diamond plates. I feel like you can set the bevel on whatever and finish it on strops like Taz does pretty effectively. I've tried it and it works great. Diamond plates are really handy tools though.

[Robstreperous]

So ... like a lot of things I guess it probably depends on who's doing the sharpening and how they're doing it.

I don't have any experience with Magnacut yet but just had my first run in with CPM 20CV on a chef knife I use a lot. I had no luck at all using my Nubatamas on it. Was sharp off the stones but the edge deteriorated in no time.

I ordered a couple of the DMD stones Mark has on this site and... problem solved. They also gave me a nice long lasting edge on a W1 Tsourkan I've had for years. I was able to sharpen that on the Nubatamas with some CBN stropping but this is a heck of a lot easier..

So there you have it... one man's experience....

[taz575]

Curious what the edge was like before you started and what Nubatama's you used?

I found the hardest part was getting the apex formed and cleanly formed on the water stone (320 Glass Stone) after the belt sander. I thought I had it done a few times and kept going back to the 320 stone when I realized that I saw flat spots after the 1200. It felt sharp, but wasn't apexed yet in some areas! The burr can be difficult to remove fully, too and may take longer/more aggressive methods.

I have some diamond stones somewhere in my sharpening tool box; I want to see how those do with the higher vanadium steels compared to the Glass Stone 320. The diamonds may help remove the burr quicker, too.

[Robstreperous]

Curious what the edge was like before you started and what Nubatama's you used?

It wasn't terrible Tim. Just past the point of being able to revive it with my strops. The first thing I always notice is the edge bouncing off of peppers and tomatoes. I remember living with that for a little bit and then not liking what was happening on onions.

I know I tend to polish my edges more than most but I wasn't doing anything crazy with this edge. Highest I ever had it would have been around 5K. I can't swear to this but I think I started that sharpening session off with a Nubatama 320. Regardless I definitely recall I needed to work pretty hard to get a burr...

[taz575]

Its a slow cutting steel for sure! I have one of the M390 Artifex from several years ago and haven't taken it to the stones in a long time. If the edge is thin, it may be flexing on the water stones, so they aren't cutting as much, or reaching the apex, where diamonds need less pressure to cut.

[Robstreperous]

Its a slow cutting steel for sure! I have one of the M390 Artifex from several years ago and haven't taken it to the stones in a long time. If the edge is thin, it may be flexing on the water stones, so they aren't cutting as much, or reaching the apex, where diamonds need less pressure to cut.

You're on the money as far as going a long time between needing maintenance. I had this one for over a year and it gets heavy (for me) usage. I almost use it like a utility knife.

Hard to say if I had an edge apex issue. This is the first time I've ever had a problem like this since around the time I was just learning to sharpen. Then again, it's also the first time I've sharpened a steel like this! Good thing it wears so well... I'd say it probably takes me 2 to 3 times longer to sharpen this knife on diamond stones than pretty much any other knife I own... Except maybe some of my old Gerber stuff... (haven't tried those yet on the DMD stones).

Just to make sure nobody takes these comments out context, Please don't get me wrong... I love the knife and this steel for this purpose. It stays sharp and I can pretty much use it and forget about it for long periods of time.. I feel like I could go a month or two without stropping if I wanted. Might even test that out.. Just truing it on balsa or leather or something...

That said there ain't no free lunches and when sharpening day comes... it's a day of reckoning to be certain... Next time I need to do it I'm going to set aside time to do just this one knife. At least for me I find I need patience and concentration.

[taz575]

I noticed the issue with the super wear resistant steels. They can feel sharp, but aren't sharp. I try to look straight on at the edge bevel to make sure there is an apex there, even after stropping. If a wire edge/burr breaks off, it may leave tiny flat spots, especially if it's a larger carbide steel and may need more sharpening after stropping and repeating the process. S90V and CPM 20CV seem to do this more than Magnacut does, so Magnacut is a bit more user friendly sharpening wise.

[ex1580]

I noticed the issue with the super wear resistant steels. They can feel sharp, but aren't sharp. I try to look straight on at the edge bevel to make sure there is an apex there, even after stropping. If a wire edge/burr breaks off, it may leave tiny flat spots, especially if it's a larger carbide steel and may need more sharpening after stropping and repeating the process. S90V and CPM 20CV seem to do this more than Magnacut does, so Magnacut is a bit more user friendly sharpening wise.

I second this. My S90V pocket knife played this trick on my for a good while. It would feel sharp but something wasn't right and it would deteriorate quickly. I was getting quite frustrated and about to Ebay the knife but as a last ditch effort I tried my Atoma plates and they got the job done. I think between the big carbides and stainless carbides it can turn into a funky mess pretty fast, haha.

My best result on S90V (and on my Maxamet knife for that matter) comes with doing just enough work on the Atoma plates followed by some stropping on diamond loaded strops. For me the 600 Atoma was plenty good enough and a 3 micron loaded strop left me with a great box cutting utility blade that has lasted quite well. For a kitchen knife I would go up to the 1200 Atoma and follow the 3 micron strop with a couple of laps on the 1 micron strop. If your first lap on the strops is a few degrees higher it helps get rid of the burr. Sometimes I do that on bare leather because I don't want to abrade the apex really, just bend the burr back and forth so it falls off. Then you can focus on just finishing the bevel refinement.

[Robstreperous]

I noticed the issue with the super wear resistant steels. They can feel sharp, but aren't sharp. I try to look straight on at the edge bevel to make sure there is an apex there, even after stropping. If a wire edge/burr breaks off, it may leave tiny flat spots, especially if it's a larger carbide steel and may need more sharpening after stropping and repeating the process. S90V and CPM 20CV seem to do this more than Magnacut does, so Magnacut is a bit more user friendly sharpening wise.

I second this. My S90V pocket knife played this trick on my for a good while. It would feel sharp but something wasn't right and it would deteriorate quickly. I was getting quite frustrated and about to Ebay the knife but as a last ditch effort I tried my Atoma plates and they got the job done. I think between the big carbides and stainless carbides it can turn into a funky mess pretty fast, haha.

My best result on S90V (and on my Maxamet knife for that matter) comes with doing just enough work on the Atoma plates followed by some stropping on diamond loaded strops. For me the 600 Atoma was plenty good enough and a 3 micron loaded strop left me with a great box cutting utility blade that has lasted quite well. For a kitchen knife I would go up to the 1200 Atoma and follow the 3 micron strop with a couple of laps on the 1 micron strop. If your first lap on the strops is a few degrees higher it helps get rid of the burr. Sometimes I do that on bare leather because I don't want to abrade the apex really, just bend the burr back and forth so it falls off. Then you can focus on just finishing the bevel refinement.

So in order to handle the burr I've been running through a cork or a felt square. Any reason, with this steel, that's a better strategy?

[ex1580]

I've got the felt block too. I use it sometimes but mostly for cleanup of a gnarly burr before finishing. I read somewhere that when you pull it through a cork or similar wood the metal from the burr builds up and makes the apex dull again down the blade. I have not studied this extensively. I have seen an awful lot of sharpeners do the method I described to fold one way then the other. It seems to work (per inspection using my microscope) so I keep doing it. I think if there isn't much burr to begin with then it will matter less. I like to keep practicing the same motion as much as possible in regard to sharpening.

[taz575]

I use the cork and felt to "rip" the burr off and then refine the apex on the stones and diamond strops after the burr is gone. The super wear resistant steels are slower to form a burr at the higher grits, so its easier to not get much burr to remove as you go up in grits.

[Robstreperous]

Thanks to both you guys. That makes a lot of sense to me.

[ValeryD]

In the thread "Sharpening HAP40"

Read my post Post by ValeryD » Mon Dec 04, 2023 4:15 am

I gave there the links to some results taken during several investigations.

The main conclution: all super steels with great amount of carbides should be sharpened only on diamond stones from the very beginning to the finish with full(!) progression.


Valery