Additional information

Weight 0,400 kg
Blade length (mm)


Blade thickness (mm)


Weight (g)

170 with sheath

Blade height (mm)




Adrian Bayer, the founder of MMB Monostahl (Messer & Mechanik Bayer), is himself an absolute knife passionate and also likes to use the knives quite hard. So it came about that he built a pocket fixed one day himself, as all folding knives did not meet his ideal of being robust enough.

Adrian’s products are supposed to be robust, versatile and compact. Wir haben es getestet und waren nicht schlecht erstaunt, was diese kleine Taschenaxt alles wegstecken kann. Die Messer werden in einer Kleinserie hergestellt und unterscheiden sich alle ein wenig voneinander, da Sie alle mit der Hand aus dem vollen geschliffen werden. Es sind keine Vitrinenmesser, sondern sie sollen benützt werden, dass ist auch genau unser Motto. Für Kunden die hier mit der Lupe kleinen Fehler suchen sind diese Messer nicht gebaut, sondern als Backup und Allroundhelfer und für die besonderen harten Fälle. Wir haben ein Test gemacht, welchen Sie sich hier ansehen können, bitte aber nicht nachmachen. Da es wirklich darum ging die Grenzen auszuloten, wie weit wir gekommen sind, sehen Sie hier im Video.

Made in Germany / Black Forest
The knives are delivered with a certificate in a box.

The 4034 steel by Adrian Bayer:

Until today and probably also in the future, various cutting tools are made with it, from razors to surgical knives with 20 cm blades, plus big names like Buck and Leatherman.

In the past, knives such as Boy Scout knives were sometimes hardened to only 55 – 56 HRC so that they would not break even in the case of rough mischief, but rather bend when overloaded. Who wants to be responsible for children who are perhaps not yet so confident in their use of knives injuring themselves? This quickly leads to the story that “the steel is bad” – although it is only the heat treatment that makes it hard or softer. Of course, there are many other correlations and also many steels that have a higher service hardness. But not all of them can be brought back to shaving hardness so quickly and easily, some not even at all (large carbides).

The “designation problem”:
1.4034 – a steel that has been around for about 100 years – is traded in the USA as “420-C” and not as “420” because it has a somewhat higher C content, about 0.43 – 0.5 %. Due to the chromium alloy with 13 %, it should behave similarly to a carbon steel with approx. 0.8 % C when well heat treated. The “normal” 420 in the USA, however, would also correspond to our 1.4028 or 1.4031, for example, both of which, however, have less C. Therefore, misunderstandings can probably arise here as well.

Here is a list:

Designation: EN-DIN: AISI:
1.4028 MO 1.4028 420X (+Mo)
1.4028 YC, YN 1.4028 AISI 420, 420B
1.4031 YA ~1.4031 AISI 420
1.4031 YC, YE 1.4031 AISI 420, ~420X
1.4034 YN 1.4034
1.4034 YS, YE, YK 1.4034 AISI 420, 420C
1.4035 YU 1.4035 AISI 420C (+S)
1.4037 YR 1.4037 AISI 420

You can clearly see the different DIN/EN standardisation of the steels, but not always so with the US designations, you could just call them all 420 and it wouldn’t even be a lie.

All in all, 4034 is a pretty good blade steel that doesn’t have any real weaknesses if it is well heat treated, but it is just not a fad with some high peaks, or great designation. In addition, there is the forgeability – which is essential for the MMB mono steel.

With the right heat treatment, a good hardness value of 57-58HRC can be achieved, with still good toughness. That is why I give the knives to a hardening shop whose core business is hardening stainless steels.

The heat treatment of the MMB mono steel looks like this:
Werkstoff: 1.4034 / X46Cr13
Vakuumhärten bis 1080° C
Tiefkühlen 4 h
5 times tempering


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