71 Rockwell C CPM REX 121 blade vs. brick

[@kknives_switzerland]

DISCLAIMER: DO NOT REPEAT THIS! A customer of mine, going by the handle @pm2og on Instagram, decided to put one of my Rex121 blades at 71 HRC to the test. This is what proper heat treat can do folks.

[@stephan123321]

Stark, also das die Schockbelastung so gut aufgefangen wurde. 🙂

[@Nudel-nc1cp]

Yikes I didn't expect this to be honest. Well done.

[@lars43771]

Bet you were clenching the cheeks together watching this one😆 I know I was!

[@kknives_switzerland]

You bet I was. But I also was confident in my product.

[@lars43771]

@@kknives_switzerland as you should be!💪

[@verdigrissirgidrev4152]

Das ist schon impossant, allerdings wäre es aufschlüssiger, zu sehen, wie oft man das machen kann, bis das Messer aufgrund der angesammelten Gitterdefekte durchbricht bzw. Ausbrüche bekommt. Selbst mit einem Gummihammer dürfte das ja an der Schneide irgendwann so laufen.

[@kknives_switzerland]

Vielleicht macht er mal weiter - was mir hier wichtig war zu zeigen ist, dass 71 HRC eben NICHT wie Glas beim ersten Schlag zerbricht, obwohl die Klinge deutlich härter als Glas ist. Der bisherige/aktuelle Konsens ist ja leider immer noch mehrheitlich, dass alles über 60 HRC schon kritisch wird, was die Zähigkeit angehet. Wobei ich argumentieren würde, dass die Druckstabilität mindestens so wichtig ist, was mit diesem Test eigentlich mehr getestet wird als die sog. "Kerbschlagzähigkeit". (Auch ein schönes deutsches Wort.) Wenn ich mal etwas Zeit und entsprechende Ressourcen habe, würde ich gerne eine Fixtur bauen, weleche diesen Test mit verschiedenen Testmedien reflektiert, aber in einer absolut kontrollierten Umgebung. Würde gerne noch viel mehr schreiben, aber muss in die Werkstatt zurück; die Messer machen sich nicht von alleine. 😅

[@sharpcokorea]

👍

[@southerncross100]

👏👏

[@kknives_switzerland]

Thanks for watching

[@sharpfactory3705]

Rex 121 auf 71hrc und so zäh das ist unglaublich. Das Messer sollte eigentlich komplett zerspringen

[@kknives_switzerland]

Ich bin sehr zufrieden mit dem Resultat

[@TimJohnson-x1o]

thats a gimmick. reminds me of BBB plucking hardwood and making dramatic cracking sounds. These are not real tests of toughness, they are parlor tricks. Go ahead and gently tap that edge on the lip of a glass or a steel mug and see what happens. Forget the dramatic hammer. Gently tap the edge onto the corner of that brick and see what happens. Strength and toughness are not the same thing. Harder steel is stronger. Harder steel is also less tough.

[@kknives_switzerland]

You seem to have missed the purpose of this test. The purpose was demonstrating to people my Rex121 at 71 HRC knives can be used without treating them like glass, which is what most people would instinctively assume. No tricks here. If you look around and check out what I do, you'll arrive at the same conclusion I hope. Also, how should a gentle tap on glass be a better test for either toughness or strength, that makes no sense. (Less amount shock won't give us any additional insights.) Side note, since you mentioned strength vs hardness correlation: this test is indeed a demonstration of strenght first and foremost, which when it comes to knives arguably is at least as important, if not slightly more important often than gross toughness. But due to the impacts generated by the blows of the hammer, toughness also is being tested here. Long story short, for the afformentioned reasons, this a good, reality based test for what advanced steels combined with thought out heat treats can achieve.

[@Laurarium]

@@kknives_switzerlandI think what he means is that the contact area is too large with full edge length, combined with a small rubber faced hammer, there is really not much impact, where as in real life, it is usually only a tiny protion contacting glass or ceramic. I understand that this test is not to boast its toughness rather than being a basic check as “It is not like glass brittle”. However, I think it is worth trying the tapping test, let’s see what happens.