K390 vs M390

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Neo

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Is this correct ?

K390 and M390 share about the same toughness.
M390 is stainless but K390 isn't very prone to rust neither
K390 has a much higher edge retention than M390 and is much more difficult to sharpen.

Has anyone experience with K390 and would you prefer it over M390 (for a fixed blade)?
 
Neo said:
Is this correct ?

K390 and M390 share about the same toughness.
M390 is stainless but K390 isn't very prone to rust neither
K390 has a much higher edge retention than M390 and is much more difficult to sharpen.

Has anyone experience with K390 and would you prefer it over M390 (for a fixed blade)?
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Can you post the toughness information for both and where you got the data? I have a hard time believing that one being stainless is as tough as the other. But maybe so.
 
Cobalt said:
Can you post the toughness information for both and where you got the data? I have a hard time believing that one being stainless is as tough as the other. But maybe so.
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They're about the same. At 61 RC A11 is 20 ft lbs, at 60 RC M390 is 22 ft lbs. That's fairly fragile for both compared to other steels that also have very adequate wear resistance. Of course, you can compensate for that fragility by making the blade thicker and thicker until it just doesn't cut anymore. Or you can get a steel like 4V that's 50 ft lbs at 60 RC that'll cut all day AND be able to withstand some decent abuse in thin grinds.
 
bodog said:
They're about the same. At 61 RC A11 is 20 ft lbs, at 60 RC M390 is 22 ft lbs. That's fairly fragile for both compared to other steels that also have very adequate wear resistance. Of course, you can compensate for that fragility by making the blade thicker and thicker until it just doesn't cut anymore. Or you can get a steel like 4V that's 50 ft lbs at 60 RC that'll cut all day AND be able to withstand some decent abuse in thin grinds.
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Ah, no wonder. Makes sense, neither is tough. ok.
 
I have a K390 mule and 3 folders in M390, BM 581 and 586, ZT 0770.
M390 is has excellent corrosion resistance. K390 needs care it will quite easily rust. That's my experience.
 
trevitrace said:
The only knife I have in k390 is a Spyderco mule, and I'd say it is much more prone to corrosion than the one knife I have in M390, a Spyderco PM2.
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Cursum Perficio said:
I have a K390 mule and 3 folders in M390, BM 581 and 586, ZT 0770.
M390 is has excellent corrosion resistance. K390 needs care it will quite easily rust. That's my experience.
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Ok m390 with 20% cr is more corrosion resistant than k390 4%...
What about the other 2 questions? I'm curious too.

BTW Bodog, k390 is supposed to be a slightly tougher version of a11/10v.
 
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jpm2 said:
Ok m390 with 20% cr is more corrosion resistant than k390 4%...
What about the other 2 questions? I'm curious too.

BTW Bodog, k390 is supposed to be a slightly tougher version of a11/10v.
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Maybe. BU states K390 J notch is about 45 joules. Don't know how that converts to ft lbs.

Here's Phil Wilson:

"CPM 10V, and**Bohler‐Uddeholm , BU K294 and BU K390,**The ASI A11 steel**
grades used for knife blades.**
How do the BU grades compare to CPM 10V?**They are all the A11 grade and the same basic chemistry
so It depends more on the heat treat and edge geometry than the make up. The BU particle process is
more refined but the particle size on all of them is so small that I am not sure the difference would show
up in a knife blade. I like all three steels. CPM 10V is about 40 years old since development and over this
time they have worked out all the potential problems. The BU versions are very nice indeed, they heat
treat easy and the finer grain and advertised cleaner mix are all welcome. Both companies have been
very helpful to custom makers. They provide good tech support and steel availability.**They are also
willing to supply material in small quantities and thickness that work for a knife blade.**
K390 has been tweeked a little with added tungsten and moly. Both these elements form carbides that
add to the vanadium carbide in the mix. The data sheet says a little less wear resistance than the std
A11. I guess that is because both moly and tungsten carbide are slightly softer than vanadium carbide.***I
have not seen that K390 has less edge holding than 10V or K294. They are all very good, in fact in the
same top category and I think it would take a laboratory and very controlled conditions to see a
difference. BU has mentioned that they are going to do some CATRA tests with K294 and K390 so when
that information comes out maybe it will tell us something more.**K390 does have the potential of
inching the hardness up a bit with a thin edge geometry or a more aggressive use with the same
geometry.**We may be talking about marginal differences but as more makers work with all three we
should get some feedback.****
Phil"
 
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jpm2 said:
Ok m390 with 20% cr is more corrosion resistant than k390 4%...
What about the other 2 questions? I'm curious too.
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I have only re-profiled and sharpened the K390 Mule once, and touched it up on the SM a few times, and haven't used it all that much. Yes it's harder to sharpen (meaning it takes longer to sharpen) than M390. I use a WE for sharpening.
The M390 blades I have, I've used a lot more. My impression is that K390 certainly does have better edge retention but I have limited experience using the K390 to be more specific.

When sharpening the K390 it 'feels' like a quite a hard steel under the stones to me, whereas the M390 has more of a wear resistant 'feel', as if the stones are more inclined to slide over it than bite.

Myself, with my limited knowledge/experience, I would prefer M390 in a fixed blade because I value it's high level of corrosion resistance, it does have pretty good edge retention, isn't hard to sharpen and touches up very nicely on the SM.

Whilst I try to share my limited experience, there are far more knowledgeable people here and hopefully you will get more experienced input.
 
Cursum Perficio said:
I have only re-profiled and sharpened the K390 Mule once, and touched it up on the SM a few times, and haven't used it all that much. Yes it's harder to sharpen (meaning it takes longer to sharpen) than M390. I use a WE for sharpening.
The M390 blades I have, I've used a lot more. My impression is that K390 certainly does have better edge retention but I have limited experience using the K390 to be more specific.

When sharpening the K390 it 'feels' like a quite a hard steel under the stones to me, whereas the M390 has more of a wear resistant 'feel', as if the stones are more inclined to slide over it than bite.

Myself, with my limited knowledge/experience, I would prefer M390 in a fixed blade because I value it's high level of corrosion resistance, it does have pretty good edge retention, isn't hard to sharpen and touches up very nicely on the SM.

Whilst I try to share my limited experience, there are far more knowledgeable people here and hopefully you will get more experienced input.
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I wouldn't really want either in a fixed blade unless it was meant for very light use in a highly abrasive environment. Otherwise there are steels better suited for wider variety of tasks in a fixed blade. Both would probably make great small pocket knives depending on your desired level of corrosion resistance.

If I absolutely needed some corrosion resistance in a fixed blade then I'd rather go with CPM 154 or CPM D2 depending on how corrosion resistant I needed the knife to be. Otherwise, again, there are better steels that can do more in a fixed blade. 3V, PD1, 4V, M4, 1095, 52100, and 5160 are much more diverse with a much higher variety of uses unless you absolutely need better corrosion resistance where elmax would be good. For the ultra narrowly defined work where knives are only needed to cut things like cardboard and rope then K390 and M390 would excel.

Of course the game changes when people start accepting really thick knives, then you can use just about anything with more or less equal results.
 
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I've knives in most steel but none in K390.
My favourite steel is VA4E very closely followed by 3V.
The custom knife maker uses both M390 and K390 so I have to choose.
I think I will go for the K390 because it's not so common and I don't have many knives in the high carbides range.

Some more comments from Phil Wilson

I may be the first maker to work with K390. I got a small sample to try from Alpha Knife supply and here is the report I sent back to Chuck and will put up on my website:
I can give some feedback on K390 based on one finished knife that I now have in my kit. This is a trailing point based on the Bow River design. I took it on a recent Mule deer hunt in Utah and it saw most of the duty from field dressing to cutting and trimming to vac pack in the freezer on two Mule deer. This is a FFG 4.5 inch blade ground to about .008 behind the sharpened edge. Hardness is RC 64. The heat treat was done based on the Bohler data sheet with the exception of an overnight subzero in LN2. I would say that edge holding in not an issue. After the use described it will still cut ¾ inch rope with less than 20 lbs on the scale. Due to the thin grind I do not pry apart joints or do any chopping so bending toughness and impact resistance still needs to be evaluated. I have not done a direct comparison of K390, K294, CPM 10V for edge holding but will say based on use in the field with all of these steels at the same hardness they are all in the same category. 10V has always been the standard that I use to compare edge holding on other grades. K390 compared to the other A11’s has less chrome and Vanadium but has added tungsten and cobalt according to the data sheet. The ideas is to improve the matrix, add hot hardness and give it better impact and bending toughness. It will take some more work, heat treating and different hardness targets to evaluate all this. Also hopefully other makers will try it and chime in as time goes on. I was concerned about corrosion resistance. So far the blade has a slight patina and no rust or pits. I left it “as is” after field dressing the last deer on the trip home just to see what would happen. Normally with these non stainless grades a good cleaning is recommended and then some mineral oil applied before it goes back in the sheath. With wet conditions then there is going to be some more serious corrosion. This is not a grade to be used in very wet conditions or around salt water. I would go to CPM S110V, CPM S90V or M390 for that application. Sharpened with a fine SC Norton stone it is a very aggressive cutter. No need for a polished edge here with this one. It also responds to a loaded strop to tune up when it loses the bite. The other thing I noted is that it “pops” nice in heat treat. This will allow the possibility of a higher finished hardness and with a little more toughness, a finer edge. Grinding and finish based on one blade is a challenge. Each maker will have to work out his techniques here. I will say use new belts and maybe stop at 220 and call it good. I hand rubbed this one to 400 satin finish and probably will not do that again. Phil
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Neo said:
I've knives in most steel but none in K390.
My favourite steel is VA4E very closely followed by 3V.
The custom knife maker uses both M390 and K390 so I have to choose.
I think I will go for the K390 because it's not so common and I don't have many knives in the high carbides range.

Some more comments from Phil Wilson
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I really like V4E too from what I've seen. Great combination of attritrubes.
 
K390 has very high hardenability (typically Rc63-64) and edge retention in abrasive environments. In my experience it tends to stain more easily than 10V, but I've never seen rust on mine. I have had very small rust flecks on my 10V.

M390 is generally not used as hardened as 10V/K390 typically Rc61-62 edge retention is good, but not in the same level as K390.

I have a K390 "slicer" ground pretty thin and hardened to Rc64. But its a slicer not a hard use knife.
I like both but I'd choose K390 over M390 in a custom.
 
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