It is important when you go to buy a sword that you have a good understanding of exactly what a full tang sword is.
In many advertisements you will often see terms such as Full-Tang, Battle-Ready or Real Beater come up. This can be somewhat misleading, if you don't know exactly what this is about, and result in life-threatening situation. But why is this so important?
You must first make a clear distinction here between a functional sword or a decorative sword. Decorative swords are for purely decorative purposes and therefore not suitable for functional use. They are to be hung on the wall or placed on a table for purely decorative purposes. There is nothing wrong with that, except when they are sold as being "battle ready". Then you may have the idea that you can train or practice with these and THAT is life-threatening. You should never do this.
A functional sword must meet certain requirements in order to handle it safely. This includes the swords steel quality, heat treatment, but also a full tang sword. In the article Buying a sword you can read more about the other aspects, but will now go a little deeper into the concept of full tang.
This is actually about the blade and the handle it should be in. I assume that the blade meets the requirements of a functional sword and focus only on the handle and tang.
Full-Tang is therefore about the blade and handle.
The blade should be forged from one piece of steel and this blade should be firmly seated in the handle. The part of the sword inside the handle is not directly visible and is therefore sort of hidden. In swords, this part is called the tang. On a Japanese sword it is also called Nakago.
The part of the blade inside the hilt may not be welded, screwed or glued. This is very dangerous because as soon as the sword touches something the blade can break in half and this can lead to serious injuries. So in decorative swords you often see rat-tail pliers that cannot withstand forces. For the user this is very dangerous but also for the people standing around.
So actually with the handle you are holding part of the blade and you only see the blade. The blade is firmly anchored in the handle by means of a good construction. This is called a full tang sword, and is an important aspect of whether a sword is functional. A functional sword is also called a battle ready sword, but is more an American term probably from the Cold Steel corner. A Japanese Katana, Chinese Sword or European Sword must actually be full tang if you want to use it.
The tang of the blade should also be forged in such a way that it is actually strong enough to ensure that the sword does not break as soon as it hits something with a lot of impact. A forge with a lot of experience will only make swords with a blade that is forged correctly full tang and will incorporate this into the design. These blades can therefore withstand the forces that are released and the blade will not break. In japanese swords you often see that the tang is ¾ width of the blade. This amount of steel can withstand any forces released during use.
Drawing 1 is a 4/5 full tang functional sword (it does not break easily).
Full tang samurai sword katana
Drawing 2 is a full tang design but is still not capable of withstanding the forces (this sword will break quickly). The tang is too thin for a battle ready sword.
The handle should also be made of solid materials and the tang or sting should be firmly anchored in there with a good connection between the blade and tsuka. In a Japanese sword, it is actually two pieces of wood that are wrapped around the tang with a wrapping and fittings. These parts must all be of good quality.
Full tang is thus part of a set of requirements that good sword must meet to be truly functional. The sword must really be designed for functional use and only then could you say it is a full tang battle-ready sword. I prefer to speak of a sword that is suitable for functional use. Swords must also be used for the purpose for which they were developed. A sword is not strong enough to cut down a lamppost. In terms of sharpness, a sword is between an axe and a razor and these are designed to attack people.
If you want to talk about a qualitative functional sword then the following aspects are important. Steel quality of the blade, adequate heat treatment, handle finish, quality control, full tang and mounting quality. You can read more about this in the article buying a Katana.