Tag Archives: Heavy Metal

STEEL K390 BÖHLER’S MICROCLEAN – UNCANNY BLADE MATERIAL.

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I have seen a video where someone is stabbing concrete with its Spyderco Police 4 to show how K390 is strong ! The blade of that famous knife is thin and this thinness is here for a purpose: Sal Glesser has decided to use the Police 4 plateforme according to his own desire but toughness and impact resistance may have weighed in on the decision. For once the Police is not especially aimed at the LEO but those ELU who use their thin knives hard !

“We make quite a few designs for the Law Enforcement market at this time, so the design for Police use is necessarily the case anymore, like it was in 1984. I designed the Police 4 to include what I would like in a knife, more than what a LEO might like. It’s still a kissing cousin, and large for most people. I widened the blade, enlarged the hole and selected a steel that I like to use. The design’s success in the marketplace is unknown at this time. But I get to have one. ” Sal Glesser.

K390 is not stainless. It’s a cold work tool steel which uses Bohler proprietary Microclean technology.  K390 has close to the same edge holding as A11 but is much tougher. Bohler’s third generation particle metallurgy contributes to the toughness of the steel.This steel will be hard to grind, finish and sharpen. Once it is sharp it will stay sharp for a long long long time. It’s CPM M4 on steroids which means K390 has more strength, durability, stability and wear resistance than M4 ! And I do love CPM M4.

Here is a video which confronts CPM M4 and K390:
https://youtu.be/TI53ziibeiQ

From Bohler’s commercial:

“K390 is quite simply the powder metallurgical cold work tool steel with the best properties for cold work applications available from BÖHLER at the moment. K390 MICROCLEAN was developed to meet the demanding wear resistance and compressive strength requirements of cutting, blanking and punching applications, for cold forming applications and for parts which are subjected to abrasive wear in plastics processing. Tool life can be increased by several hundred percent due to the outstanding wear resistance, high compressive strength and good toughness of BÖHLER K390 MICROCLEAN. These material properties enable our customers to make their production processes more efficient and consequently to reduce the price per part produced. Too hard to be machinable? Quite the opposite. The task of the tool steel manufacturer is to produce a steel which is, on the one hand, easy and economic to machine (with a hardness of around 280HB) and simple and unproblematic to heat treat, but which, on the other hand, has a very high hardness (up to 64HRc) and optimum performance in use. The secret lies in the powder metallurgy process. A very fine, homogeneous microstructure guarantees optimal machinability.

K390 owes its superior properties above all to the powder-metallurgical production process. The main advantages of BÖHLER MICROCLEAN steels over conventional steels are: • uniform carbide distribution • small carbide size • uniform chemical composition over the entire cross-section and length • virtually isotropic behaviour due to improved homogeneity and the absence of segregations.”

From Phil Wilson on the Spyderco Forums.:
“I have been using K390 from the start ever since it was introduced by Bohler and I got some small samples to try. A bit of history is that it is the European version of CPM 10V but not the exact chemistry (about 1% less V plus small addition of a few others). That is because the CPM 10V chemistry was protected by patent at the time. If you check the K390 data sheet it claims that the bit less V gives K 390 a little boost in impact toughness. It also can be heat treated at a lower temp. than 10v. So it is pretty much the same as the A11 grade but different in a few small details. It is hard to tell the difference between CPM 10v and BU K390 in the real world in my experience. I like both grades and they are the base line (along with Vanadius 10 and K294) from which I measure wear resistance. The 5 chrome is there to make them all air hardening among other things and does not contribute much to corrosion resistance. It is going to make a killer knife in the new offering and be another classic. Phil”

On my Urban, K390 has proven to be very tough. It is my main travelling folder. And it is a real wolf under sheep’skin. One of the little home test I got is by removing the metal around a bottle of wine’s cork. Most of the time, the knife edge is bent and shows some shining due to miss alignement but not with K390. The steel feels like plastic. On my three knives, the Pingo got the most stout blade and less pointy. This little knife is simply used very hard with zero damage to the edge: digging in wood, cut into staples, scrapping various paints and plastic. So far, even if the steel is not stainless, a mild patina has protected it from real rust.

So what do we got ? A tough blade which keeps its sharpness for a very long time. A forgiving edge which can be used by clumsy hands with no after thoughts.
The side effects are: the need of diamonds and ceramics to keep it razor.
Once convexed to me taste, I use white ceramic and some stropping just to get it mirror.

We definitively needs more knives in K390 !

 

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Patina on Cruwear ? Not that easy !

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Forcing a Patina on Cruwear!
Why?
Because I’m going to the sea and I just need to be certain it won’t pit.
Now Cruwear seems tricky compared to 52100 or Maxamet.
Let see how it will get…

 

45 minutes later… No patina yet some stains…
“It’s not as rusty as 1095 usually, so it’s easy to get complacent. It can go 3-4 days easier than O-1 or 1095 but 3-4 months is a different story. It’s easy to get fooled by steels with this level of chrome ( 8%) as to corrosion resistance. It will appear as a tiny spot of rust. Easy to overlook as it does not make it apparent that spot is deepening, not getting wider. The surface layer of rust covers up the hole. ”
The Mastiff

And he was right…

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Trying to mix oxygen and vinegar using tissues and apple vinegar ?… Nope.

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Apple vinegar and apple sugar under the sun….. Nope.

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Aceto di Modena…. nope.

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Even in the wind…

Naaah forget it. This steel won’t stain beautifully… Just a bit but not enough in my taste.
It will perhaps pit if let unclean some weeks but in my daily uses it should not.

Putting the blade back in the handle the tolerances on that knife are so great you can tight the screws with locktite and pur a drop of nano oil… the pivot is smooth as butter.
Also ten passes on white ceramic and it is back to jumping hairs harvest again.
So cruwear seems to be a very “friendly” steel which doesn’t smell anything when confronted to apple, apple vinegar, various vinegar including aceto … nothing seems to harm it surface.
It is like CPM 3V and will be kept oiled and shiny. My Ed Schempp’s Tuff never needed or develop a patina as my grey Military in Cruwear.
At least I got less worry. 🙂

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The Spyderco PPT Round 2 — The Son of Anarchy.

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Strangely I am coming back often to the PPT when I first thought it would be a collection and a safe queen. Safe queen my a$$ ! Pardon my French but there is something quite sensual when holding this knife, something which makes the other feel “hollow” in comparaison. The PPT got that heavy butt “anchoring” it to the palm but also the toxicated finish of the handle’s slab is a delight under the thumb.
There is something almost “paleo” in the finish. Something primal in the mechanical way it feels. It’s dense but is designed to be heavy metal. It’s a knife Opie could have admire…

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On the performance side, I have decided to get a convexed edge. Diamonds are the only language stubborn S90V seems to understand and scratches on the blade side are, well especially for the clumsy sharpener, something hard to avoid especially when using the stone at a 10° angle to get rid of that secondary bevel. The performance in pushcutting are really enhanced now. I can measure it to the Manly Peak and its thin S90V blade.

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I use white ceramic to make the steel shiny but S90V is really a tough cookie in the kindergarden of alloys: it’s a game of patience to obtain a nice finish.

But now on plastic I can enjoy the enhancement of that already very thin edge. It goes easy through.

Someone asked me why using a workhorse knife on tomatoes ? Tomatoes may look like some fragile fruits but they are not: their skin got no pity for any dull knife and their flesh will give in under any pressure. The best tools for tomatoes are serrated and micro serrated knives.

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Hence that test on my polished edges. You need a very keen blade to push cut in a tomato and make thin loaves. Plastic and bambou can be used to test the edge stability which often is only due to thermic treatment of steel.

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The alignement of the point on the PPT is very different from my Millie and is very close to the experience of the YO2: its makes powerful cuts.
Also the handle makes Icepick/reverse grip very confortable, knowing this is the favorite grip of Philippe Perroti on Fred Perrin’s La Griffe, a grip I have found handy in forcing a door. Just kidding but the confortable reverse grip (à la “griffe de chat” in French) is not a joke.

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You get also an excellent blade/handle ratio for a choiled knife compared to my Para3 for example.

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And as good as the non-choiled Sliverax !!

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My PPT has been used in the kitchen is not easy to clean because the way the hole in the liners are not accessible. This is serious issue if, for example, a piece of raw meat get stuck there and could contaminated the blade. The full Reeve Integral Locks are the best lock for checking your folding for any debris. I would have preferred solid titanium liners without that hidden cheese holes which ask for special maintenance starting by unscrewing the slabs to get full access and complete cleaning.

So in a wrap, the PPT is a compact hard user with very high performances featured by great ergos. It has a really strong character (it feels like it has been done for some Hell’s Angel fan) but once deployed it will pierce and cut with high reliability. Once the PPT is entering the game: this is serious business. For the record Fred Perrin was often one of the knifemakers going faithfully to bikers gathering. Bikers love La Griffe as a neckknife is handy on a ride. So it’s easy to understand some DNA in the PPT design.

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