I too learned what clint said but that is only one theory and is actually questionable. If your sword cut it's way into it, it can also cut it's way back out and there is no real evidence that this was the real reason. One thing is for sure though if you ever held a sword without a blood groove and one with the blood groove the one with the blood groove is generally much better balanced. Without the blood groove the swords tend to be top/blade heavy which after much practice/fighting wears you out. A sword balanced more towards the handle is much better. Even removing that little of metal can make a difference. Another theory is that it was ornamental. Don't know about that idea either. In truth we can only guess and really don't know with real certainty.
In terms of European terms it is called the Fuller, In Japanese it is a Hi, or Bo-hi (Usually written Bo-bi)
Blood Groove is a terrible name since it has given way to misinformation. There has been a continuing thought that the "blood groove" stopped the sword becoming stuck in the body or that it helps bleed the target when stabbed, this is not the case. The objective of the indent is to lighten the blade while maintaining strength, and always has been.
We tried a number of blade styles on pig carcasses and the vacuum effect had no issue on long blade weapons and was only obvious in daggers and other short blades. As for bleeding, the wounds created from piercing each did their job to varying but lethal effect anyway.
In Iaido the Hi is popular since it makes a distinctly louder sound on swinging and results in a clear difference between perfect cutting angle and when the blade is slightly off.
That my friend is called a fuller. It was done for the same reason they make I beams; that is to make the blade stronger without the added weight. It was not a "blood groove", it was sometimes incorportated in with the ornimentation. There were several designs over the centuries, the most common being a single fuller (one on each side) but there were swords made with with doubles and an asemetrical pattern were 3 on one side and 2 on the other.
It's a blood Groove. Generally used for swords that were able to be thrusted into your opponent. the groove would prevent suction (like if you put you foot in quick sand it would provide resistance against being pulled out)
The grove prevents this and allows you to remove the sword and continue on your spree of carnage.
Exactly what the two before me said. It is called a fuller.
Hey, I've got a little question, on most swords you see a line on the blade, it's like 0.5 cm deep i think... What is it for?
