m390 tough enough ?

C

caseynz

Joined
Apr 1, 2007
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I recently made a hunting skinning knife for my father. I have made plenty of knives and am fairly confident in my ablity to make a decent knife. I got the steel heat treated by a professional heat treater to 62 rc. my father has chopped up a few deer with the knife and it has performed well, holding an edge as it should . But, on the last deer he went to cut out the stags eye teeth ( he saves them as they are ivory ) and he snapped off a good half an inch of the tip. on inspecting the knife I see another small chip further up the blade too . now before you start saying he shouldn't be prying teeth out with a knife,he has a big jar full of stags tusks,and he hasn't had this problem before . what is your opinions on m390 ? keep it for the kitchen ?
 
M390 might be tough enough, but probably at a lower rc. I think a tougher steel like cpm 3v might suit your father's application better.
 
caseynz said:
I got the steel heat treated by a professional heat treater to 62 rc.
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Question 1:

How was it heat treated?

That is my first question because M390 can be temperamental from my discussion with a few makers. Knowing a bit more on the specifics for heat treatment can help everyone identify possible issues.

Question 2.

How thin is the blade ground?
 
I do not know the details of the heat treat unfortunately all I know is it was done by a large , reputable business. The issue could be with an incorrect heat treat , that is why I have asked for other peoples experiences with this steel so I can form an opinion on it myself. the knife was ground reasonably thin at the tip , but I have also made a filleting knife out of the same barstock that is lasting well.
 
Why would anyone think that a high carbon, high chrome stainless steel, Rc'd to 62 is going to be tough. And I bet it has a thin grind as well, typical of a good cutter which is what that knife was probably meant to be. Definitely the wrong steel for the job.
 
Cobalt said:
Why would anyone think that a high carbon, high chrome stainless steel, Rc'd to 62 is going to be tough. And I bet it has a thin grind as well, typical of a good cutter which is what that knife was probably meant to be. Definitely the wrong steel for the job.
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I tend to agree with you but there are a lot of people on this forum that would argue it is though enough.

I think a slightly thicker geometry might have been the key here to prevent such failure (assuming everything with removal of can of the M390 prior to HT, and all other steps were done correct).

I have had good experiences with M390 in customs ground to 0.01 of an inch (0.025mm) and slightly below. But for the use as described that would be slightly too thin. For general neglect I would prefer around 0.04 of an inch (1mm).
 
Maybe try M4 or D2 next time you make dad a knife. I'm not sure what model knife is best for digging teeth out of a jaw. I'm thinking a chisel or a very thick bowie might be better.
 
Just what happens when bone meets knife. I've enjoyed M390 in the backcountry as well as commercial kitchens with no issue. Maybe buy some old stainless dental gear for the tusk removal?
 
Without pics, my best guess is a thin blade profile with a 62 rc, made one heck of a slicer, but a pryer it was not...

I've been under the impression m390 is very similar to s30v in regards to edge retention and high carbide cutting ability. It has a small bit more carbon whereas s30v has a nitrogen boost, but when you figure the much higher chromium content giving its great stainless attributes, and all others things combined, it has something like 6% less (softer) iron then s30v within the matrix, which would do it no favors in terms of chipping under hard use at a high rc.

It's "tough enough" to probably dress deer, boar, bear, elk and moose for years and years on end... But you probably want to;
A) go for a slightly lower rc like 60 for a field knife vs. a kitchen knife, (Bradford shoots for 61 on the guardians)
&
B) use it for all your cutting/slicing tasks, but keep a rugged thicker bladed, thicker spined folder handy specifically for any prying tasks...
 
yes, my reason for being disappointed with the m390 was that I have made him knives from o1 and 52100 etc in the same sort of profiles, lower rc of course , and they have had the same abuse for years , and lasted well . I guess I thought this super steel would handle better. next time I will shoot for a slightly lower rc and slightly thicker grind.
 
The super steel would have held up better, in terms of edge retention and stainlessness, which is what m390 is "super" at...
s35vn would be much better super steel for "toughness", it likely won't hold an edge quite as well as m390, it will still hold an edge better then your standard varieties, and still has enough hard carbides (with niobium) to be a solid slicer, but the overall alloy leaves it still having a higher % of iron remaining, with tungsten, cobalt, and nickle added to help improve toughness.

n690co, even vg10, 154cm, aus10 should all be "tougher" then m390, but "toughness" wasn't the primary goal of m390...
 
I think M390 makes for a better EDC steel than skinner or hard use steel.

I'd go with 3v, like Focusblade said.
 
Fair enough...
[video=youtube;HXbk1s3T8k8]https://www.youtube.com/watch?v=HXbk1s3T8k8[/video]
 
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There are a couple of threads discussing this. Here you go:

http://www.bladeforums.com/forums/s...-Toughness-Expansion-on-Charpy-C-Notch-Values

http://www.bladeforums.com/forums/showthread.php/1305088-ZT-0180-Hard-Use

http://www.bladeforums.com/forums/s...-Edge-Retention-cutting-5-8-quot-rope/page134

The short answer is no, there aren't many stainless steels that can be used for really rough work and still be thin enough to be useful as a cutting implement. These links have real tests, real science, and real discussions with other links to materials science studies, depending on what you really want to look at. There are some steels which will work for these rough jobs and they will not generally be stainless. They won't rust if you look at them wrong, but they can rust if really neglected.
 
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caseynz said:
yes, my reason for being disappointed with the m390 was that I have made him knives from o1 and 52100 etc in the same sort of profiles, lower rc of course , and they have had the same abuse for years , and lasted well . I guess I thought this super steel would handle better. next time I will shoot for a slightly lower rc and slightly thicker grind.
Click to expand...

O1 and 52100 are likely a lot tougher than M390, but probably won't hold an edge as long and aren't nearly as stain resistant. There is a tradeoff- you can get good toughness or good edgeholding, but it is hard to get both at the same time. Also they always say that it takes a combination of good steel, good geometry, and good heat treat to make a knife with good performance.
 
Brew-Jitsu said:
Survive! Knives did well with M390 in their GSO 4.1, but no idea what the hardness was.
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Note Jim Ankerson's post...it's VERY likely that he had tested a GSO M390 sample knife for hardness...

I have owned four of Guy Seiferd's GSO series knives...one was a 4.1 in M390 which I gifted to one of my sons.
His knives and his steels are excellent... I've had them in M390, CPM-3V and CPM-20CP.

This is from Guy's web-page. Note that CPM-20CV and M390 are chemically identical. From one web-source...
M390 / CPM 20CV is a PM stainless steel that offers good wear resistance with excellent corrosion resistance through the use of high chromium and vanadium content. The PM process combined with the high chromium content imparts M390 / CPM 20CV with good grindability and excellent polishability. Its high austenizing temperature imparts M390 with a high attainable hardness of RC 58-62.

from Guy Seiferd's site... (in bold print)
About CPM-20CV: CPM-20CV is a very high quality martensitic stainless steel, with outstanding corrosion resistance and excellent edge holding. CPM-20CV does lack the impact toughness of CPM-3V but being made with the CPM process, this steel is still very resistant to lateral stress (flex) breakage. Consider CPM-20CV for a very low maintenance, all weather cutting tool.

What is the Rockwell hardness of your knives?
All of our blades made with CPM steels are expertly heat treated to 58-59 Rc. Our S7 blades are expertly heat treated to 57-58Rc. All of our blades undergo multiple tempers and a cryo treatment, to maximize toughness and longevity.
 
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For a job that requires toughness and strength, there are many choices. M390 is not one of them.
 
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