CPM M4 vs K390

[MacLaren]

Agreed, highest wear resistance and edge stability in a Spyder currently.

Really a better comparison is the Rex 45 vs K390.
Not M4.

I still put K390 a tier above Rex45.

Just has more aggression.

Top dawg for me is still definitely Maxamet but K390 seems more friendly in the sharpening and durability department.

I haven't seen my K390 Police rust due to cutting different types of foods or moisture in general. Just a very, very mild patina. Almost let down with how little patina it shows.....I was hoping to develop a strong natural patina by the time it warmed up.

My sweat makes it get small orange rust spots, but nothing else has caused it to rust for me. That's pretty normal for any blade steel for me, even stainless.

If corrosion resistance isn't a big concern, I haven't seen a better steel for folding knives than K390. I'm generally a fan of simple steels that are quick to sharpen, and don't place muchvvalue on edge retention....but K390 is very impressive stuff.

I've never seen a steel cut so much cardboard and still have a shaving sharp edge. I touch my knives up when they stop scraping arm hair, so I don't care about how long a steel holds a working edge. Most high edge retention steels seem to lose shaving sharpness pretty quick, but not K390. I'm glad I gave it a shot.

K390 and CTS204P both impress me with their combination of edge holding and ease of sharpening. I feel like both are easier to sharpen and quicker to reprofile than S90V, S110V and Maxamet (Though I've only tried those steels briefly, one knife each). I hope to see Spyderco using more of each.

I agree 100%
Love both of them too.

[Deadboxhero]

Not a big fan of the 204p on production knives or any of the 20cv and m390 stuff with my personal experience. I prefer a harder matrix at 62rc plus with a chemistry like that, I like a stronger apex.

I'd like it more if it was harder which it's fully capable of going to 64rc but then it would be more brittle in a bad users hands so I understand why it's about 60rc.

LOVE the K390.

The Maxamet will behave differently when finished with a bonded diamond/CBN stone

Agreed, highest wear resistance and edge stability in a Spyder currently.

Really a better comparison is the Rex 45 vs K390.
Not M4.

I still put K390 a tier above Rex45.

Just has more aggression.

Top dawg for me is still definitely Maxamet but K390 seems more friendly in the sharpening and durability department.

I haven't seen my K390 Police rust due to cutting different types of foods or moisture in general. Just a very, very mild patina. Almost let down with how little patina it shows.....I was hoping to develop a strong natural patina by the time it warmed up.

My sweat makes it get small orange rust spots, but nothing else has caused it to rust for me. That's pretty normal for any blade steel for me, even stainless.

If corrosion resistance isn't a big concern, I haven't seen a better steel for folding knives than K390. I'm generally a fan of simple steels that are quick to sharpen, and don't place muchvvalue on edge retention....but K390 is very impressive stuff.

I've never seen a steel cut so much cardboard and still have a shaving sharp edge. I touch my knives up when they stop scraping arm hair, so I don't care about how long a steel holds a working edge. Most high edge retention steels seem to lose shaving sharpness pretty quick, but not K390. I'm glad I gave it a shot.

K390 and CTS204P both impress me with their combination of edge holding and ease of sharpening. I feel like both are easier to sharpen and quicker to reprofile than S90V, S110V and Maxamet (Though I've only tried those steels briefly, one knife each). I hope to see Spyderco using more of each.

[hambone56rx]

Thanks for the feedback. Holding off on the M4 Shaman then. Will wait for the P4 LW in K390 and the Shaman with Micarta Handles. Maybe the Shaman will come with K390!!

Hamilton

[Deadboxhero]

Good choice! Errmahgurd! That would be awesome! :D :D :D

Thanks for the feedback. Holding off on the M4 Shaman then. Will wait for the P4 LW in K390 and the Shaman with Micarta Handles. Maybe the Shaman will come with K390!!

Hamilton

[ZrowsN1s]

I've put a cbn low grit edge on my police 4 and carried that around for a week, the other day I gave it the ultra fine stone and 1micron cbn on leather treatment. Not sure which I like better, different animals. Took a good chunk of time to reprofile the factory edge, but it touches up quickly.

Much like maxamet I have found stropping can really help refine the edge. Must be the high wear resistance, but you can really go at it on the strops without wrecking the edge even if you get a little squirrelly with your angle and pressure. Of course try NOT to do that, but it seems a lot more forgiving than some other steels.

Unless Spyderco has plans to make a K390 or Maxamet Native *Shaman* in the near future, I think I need some more M4 in my life. I agree with BBB that M4 has been dethroned as top dog, but it has been and remains a favorite. And currently it's easier to get than the big dawgs.

[TomAiello]

Unless Spyderco has plans to make a K390 or Maxamet Native in the near future, I think I need some more M4 in my life. I agree with BBB that M4 has been dethroned as top dog, but it has been and remains a favorite. And currently it's easier to get than the big dawgs.

Maxamet Native is standard production, and is in stock with most retailers.

[anagarika]

Short answer from my experience, Yes.
I just wouldn't be able to get the edges as crisp at 1000 grit without a type of bonded diamond/cbn.
The diamond/CBN compounds on leather are a nice touch as well after the edge is very very sharp on the stones, the strop gives it a boost in the finesse.

Coated diamond/ CBN is too coarse if you want more push cutting. Too deep a cut, the abrasive grains are fully exposed and penetrate the bevel making a very ragged cut. (Great for draw cutting, like a microscopic serration)

I've seen people get by with a SiC "Norton Fine" 325 grit if one likes that type of toothy edge.

I like 1000 grit (800-1500) 20-10um, I like the blend of polish and toothy.

That works best for the variety of uses I like, a little blend of push cutting precision and draw cutting aggression but best at neither.

... but K390 seems more friendly in the sharpening and durability department.

K390 still needs CBN or diamonds for sharpening, right?

Shawn, will going up to EEF (8000) after 1200 EF on DMT help to achive smooth but toothy?

[Deadboxhero]

Short answer from my experience, Yes.
I just wouldn't be able to get the edges as crisp at 1000 grit without a type of bonded diamond/cbn.
The diamond/CBN compounds on leather are a nice touch as well after the edge is very very sharp on the stones, the strop gives it a boost in the finesse.

Coated diamond/ CBN is too coarse if you want more push cutting. Too deep a cut, the abrasive grains are fully exposed and penetrate the bevel making a very ragged cut. (Great for draw cutting, like a microscopic serration)

I've seen people get by with a SiC "Norton Fine" 325 grit if one likes that type of toothy edge.

I like 1000 grit (800-1500) 20-10um, I like the blend of polish and toothy.

That works best for the variety of uses I like, a little blend of push cutting precision and draw cutting aggression but best at neither.

... but K390 seems more friendly in the sharpening and durability department.

K390 still needs CBN or diamonds for sharpening, right?

Shawn, will going up to EEF (8000) after 1200 EF on DMT help to achive smooth but toothy?

You'll have to play with it, I've had no luck with the EEF and the EF. I have a diafold interrupted surface. Not a fan. Just my experience. Ive seen other sharpeners use the EF and EEF and the Spyderco UF. Just not my tempo.

[ZrowsN1s]

Unless Spyderco has plans to make a K390 or Maxamet Native in the near future, I think I need some more M4 in my life. I agree with BBB that M4 has been dethroned as top dog, but it has been and remains a favorite. And currently it's easier to get than the big dawgs.

Maxamet Native is standard production, and is in stock with most retailers.

hahaa. I meant shaman. I actually own the maxamet native. Thanks for the correction :D

[vivi]

Short answer from my experience, Yes.
I just wouldn't be able to get the edges as crisp at 1000 grit without a type of bonded diamond/cbn.
The diamond/CBN compounds on leather are a nice touch as well after the edge is very very sharp on the stones, the strop gives it a boost in the finesse.

Coated diamond/ CBN is too coarse if you want more push cutting. Too deep a cut, the abrasive grains are fully exposed and penetrate the bevel making a very ragged cut. (Great for draw cutting, like a microscopic serration)

I've seen people get by with a SiC "Norton Fine" 325 grit if one likes that type of toothy edge.

I like 1000 grit (800-1500) 20-10um, I like the blend of polish and toothy.

That works best for the variety of uses I like, a little blend of push cutting precision and draw cutting aggression but best at neither.

... but K390 seems more friendly in the sharpening and durability department.

K390 still needs CBN or diamonds for sharpening, right?

Shawn, will going up to EEF (8000) after 1200 EF on DMT help to achive smooth but toothy?

Isn't the Fine supposed to be around 1200 grit, and the EF over twice that? I could be wrong, but I have a fine I used for "polished" edges for a long time. It always seemed to produce bevels in between thepolish I'd get from my medium and fine sharpmaker rods.

Either way I think the medium rods or DMT fine is about as polished as you'll want to go for a relatively smooth but toothy edge. More polished than that and you'll be getting too smooth for good toothy slicing aggression in my experience.

With a lot of knives I won't even go that high. This 6" Extra Course DMT is my old reprofiling stone, before I invested in a 8" XX Coarse:

https://www.amazon.com/DMT-W6XP-Diamond ... way&sr=8-7



It makes a very nice finishing stone for when I want a toothy edge. I have no issues getting hair popping edges off of it, which surprised me the first time I tried. It cuts very clean.

IMO the medium stones from Spyderco are the best in between finish, great for EDC's, then I go more or less polished for more specific use knives.

[Chumango]

DMT fine is supposed to be 600, EF is 1200. But his depends on how new they are. A new one is much more aggressive than one that has been used a while and broken in. I like the mellowed out version that has been used. This puts the Spyderco medium rod between the DMT fine and EF, the Spyderco white rods finer than the DMT EF.

[vivi]

DMT fine is supposed to be 600, EF is 1200. But his depends on how new they are. A new one is much more aggressive than one that has been used a while and broken in. I like the mellowed out version that has been used. This puts the Spyderco medium rod between the DMT fine and EF, the Spyderco white rods finer than the DMT EF.

That's surprising to me because the DMT fine I have leaves a more polished appearance than my medium rods or stone. Then again my DMT fine is nearing 20 years old at this point, so it's very worn in. Still works great!

[anagarika]

I have two EF: the credit card & diafold (with EEF),
And two EEF, one quite worn, one is the double wihh above EF.

Thanks for responses.

[steelcity16]

Is K390 the M4 killer? It is a fantastic steel.

2 years later, I think the Military 2 Steel Poll has answered this question. There we 0 votes for M4, so I replaced it in the poll with S45VN! K390 is in a solid third place, right behind the ever popular Cruwear. Or maybe BHQ has put out so many M4 models that people or bored with it. I'm interested in more real comparisons. I'm not really a big M4 fan, so I am curious how I am going to like K390. I'll be picking up a few from the Seki Sprint series to try for sure. Maybe some comparisons to Rex45 as well would be helpful?

[abbazaba]

Upward and onward. M4 is still my benchmark, but K390 (and REX45) have really impressed me. Why would I vote for an M4 Military when I already have one :)

[Pelagic]

M4 is a great all around steel. BBB however made it apparent that there is a huge difference in strength between M4 and K390. M4 is probably a tad tougher, but at 65 HRC (K390) vs 62-63 HRC (M4) that's expected. Sharpenability seems to be very similar imo, yet edge holding and apex strength is far in k390's favor.

[jpm2]

I think both steels with good heat treats at ~65 hrc would be a closer match, k390 with more edge retention, m4 taking less damage in rough use.... maybe.

[Doc Dan]

Is K390 the M4 killer? It is a fantastic steel.

2 years later, I think the Military 2 Steel Poll has answered this question. There we 0 votes for M4, so I replaced it in the poll with S45VN! K390 is in a solid third place, right behind the ever popular Cruwear. Or maybe BHQ has put out so many M4 models that people or bored with it. I'm interested in more real comparisons. I'm not really a big M4 fan, so I am curious how I am going to like K390. I'll be picking up a few from the Seki Sprint series to try for sure. Maybe some comparisons to Rex45 as well would be helpful?

You won’t like K390...you’ll love it.

[Slash]

M4 cuts better. I only say that cause I don't have k390.
I care more about knife design than which steel it has.
Thought part of the knife enjoyment and experience was sharpening it? Wouldn't have to do that if it was a super magic steel that never dulls...

[Pelagic]

M4 cuts better. I only say that cause I don't have k390.

Haha!