What is a crook

Why is a "katana" (Japanese sword) curved or why is the scimitar crooked?

Truly a question that moves us deeply. Simple question, simple answer, right?

One possible answer would be, for example, the blacksmith tapped a little too much of the rice schnapps at the barrel and missed it while forging. Whoops, that part was crooked! It doesn't look bad, so a "fashion trend" has been set and all the other blacksmiths bend their swords and sabers to follow the new fashion.

NOT CORRECT!!!

The other answer is a little more complicated and has to do with the mix of materials used.

To explain the matter, let's go back to the beginnings of iron processing.

In the past it was very costly to first smelt iron out of iron ore. In order to make steel out of the iron, an immense amount of time and resources had to be invested.

It is understandable that at that time the whole sword was not made out of steel, but rather a material mix of "cheap & soft" iron and "expensive & hard" steel was chosen. Another positive aspect was the fact that the soft iron protected the hardened steel from breaking.

Last but not least!

Of course, various working techniques have changed over time.

The Japanese are particularly conscious of tradition, which is why the original structure of the blade has been preserved here.

In the Orient, the blade structure has continued to develop. The mixture of steel and iron was pushed on and on until several hundred layers were often found in the saber. This layer structure is called DAMAST.

If you make a saber out of this damask, it won't bend anymore.

What remained is the crooked shape, only that it has now been forged and has not been created during hardening. Also a way of maintaining tradition.

PS: Another addendum! The "crooked" shape has also been retained because of another circumstance. In combat, the curved shape of the blade had the advantage that it created deeper wounds. This design was and is more effective as a weapon.

MOOCit question

In which operations (in which order) is steel hardening carried out?

workpiece heat, Temperature hold, Workpiece scare off, directly afterwards the workpiece start.