PM2 K390 Hardness

DeadboxHero

DeadboxHero

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Mar 22, 2014
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Here is the hardness for the Bento Box PM2 in K390.
4BhPC62.jpg


@jcoolG19 also had gotten 63.5rc
So these are running 63-64rc
 
Could you explain what this reading actually means and why it is good or bad to an uneducated dummy like me?
 
boss_crew said:
Could you explain what this reading actually means and why it is good or bad to an uneducated dummy like me?
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Spyderco has a reputation of getting more out of there steel performance due to proper heat treats. Super steels have an advantage when “baked” properly. For instance, in theory, S35VN ran at 56 HRC won’t provide much advantage over 420HC or 440. S35VN at 59HRC is gettin much more out of the steel, a good balance of toughness and wear resistance. S35VN at 66HRC I’m sure is more than the steel can handle in the application of a knife; it would be very chippy. Just what I have read.
 
One concern is that Spyderco doesn’t keep many (or any) extra blades for these unique sprints/exclusives. So if I’m running my s110v PM2 and it chips badly or breaks it’s not a big deal, but with K390 I’m pretty sure you’d be out of luck once the run is done. That said, I think that a large number are being made.
 
boss_crew said:
Could you explain what this reading actually means and why it is good or bad to an uneducated dummy like me?
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It means it's hard, which means the edge may be stronger and less prone to rolling and wearing down, holds the carbides better. All at a trade off to making a better axe or crowbar, of course K390 would be horrible for that application even at low hardness because carbide volume itself reduces shock resistance and impact toughness. Most the production super steels are about ~59-60rc.
Carbides in the steels are much harder than the surrounding matrix, we don't measure carbide hardness with HRC testing but They do play a complex role in contribution to the matrix, there are different kinds, Different hardnesses and sizes and contribute in different ways.

So HRC is only part of the story.

Generally speaking, most mass produced, low end knives in lower tier steels range from 50-58rc. There are always expections of course.

Rockwell alone can't tell the whole story. The steels are made up of different things that make different structures from different chemistres and HT with advantages and disadvantages usually with inverse relationships. No free lunch.

So not something to get extreme tunnel vision on, but a nice factor to account for.
 
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What are folks experience with this steel?

I've had my K390 PM2 for about 3 weeks now. It was NIB when I got it (second hand) and had the standard spyderco-sharp (read - very, very sharp) edge. I took it to my extra fine rods until I could feel a faint burr, and then stropped it, to get it just about hair whittling. It was sticky fingerprint sharp, but not hair whittling. It took very little to get it to the next level sharp.

I have been using it daily to cut veggies and fruit and general kitchen use. A little patina is forming.

I have purposely been using it on a Corian cutting board, which is murder on just about any other knife I have. I really don't know why I have this cutting board, honestly. Ordinarily, it does so much damage! I have even been using the K390 PM2 with draw strokes with the very tip on the board. Chopping through carrots. Slicing tomatoes. Lots of edge contact.

ZERO damage, even on the tip, in 3 weeks. I am really, really impressed. It's still fingerprint-sticky sharp. No discernable chips or rolls. Just heckin sharp!
 
I'm really happy with my K390 PM2 from Bento Box. I have not done edge retention tests on it, but anecdotally it's really good and takes a great edge.

I bought the knife intending to modify it with Micarta scales however the action, detent, and smoothness of it are extraordinary. It's far better than any other PM2 or Para3 that I own. It's so good, I cant bring myself to crack the threadlocker on the pivot.
 
SubMicron said:
I'm really happy with my K390 PM2 from Bento Box. I have not done edge retention tests on it, but anecdotally it's really good and takes a great edge.

I bought the knife intending to modify it with Micarta scales however the action, detent, and smoothness of it are extraordinary. It's far better than any other PM2 or Para3 that I own. It's so good, I cant bring myself to crack the threadlocker on the pivot.
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Mine is completely opposite. Though I've lubed it, it does not drop shut and needs to be pressed closed.

That said, have I tried to adjust it? No. I'm completely satisfied with the construction, centering, detent and edge as is.

I have some that drop shut, I have some that do not. Makes no real difference to me either way.
 
I had the sharpening gear out yesterday and again this evening. I put a screaming sharp edge on my GB2 yesterday, and man was I tempted to really work up a nice polished edge on the k390. I prefer a little bit of a toothy edge. A fine polish/mirror edge is showy and doesn't last very long. But something tells me the k390 might be juuuuusssst fine with a polished edge that lasts and lasts.

Trouble was it just doesn't need even a little touch up yet. Still sharp!!
 
So im just really learning about steels, how does s110v and m390 compare to k390 assuming each is properly heat treated.
 
awd_xtc said:
So im just really learning about steels, how does s110v and m390 compare to k390 assuming each is properly heat treated.
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  • M390 and S110V are both stainless, K390 is not.
  • S110V beats M390 in wear resistance and will hold a toothy edge longer
  • S110V can be relatively brittle.
  • M390 is better balanced than S110V, its stronger, and quicker to sharpen.
  • K390 is harder, tougher, stronger at the apex, takes a better edge, and holds it longer than M390 or S110V.

As long as you're ok with maintaining a non-stainless steel, which isn't difficult, K390 is the superior steel. K390 is easily one of the best steels you can get if you want very high performance.
 
awd_xtc said:
Ok gotcha, how about maxamet vs k390. Is maxamet really that much more brittle than k390?
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Maxamet isn't brittle but its highly vulnerable to side-to-side lateral forces.

K390 isn't the toughest steel, but in general use, its tough. K390 can take the pressures that Maxamet cant handle.
 
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