The method of making a tsuba steel with tekkotsu
Some old tsubas wear TEKKOTSU.
As we come close to modern age, a powerful tekkotsu becomes rare.
Now, let's have a look how to make a steel for such tsuba.
Recently, one tsuba maker revealed his method for making tekkotsu. He had been studying Owari tsuba for many years.
The tsuba made by him wears many visible tekkotsu and are a good copy of the Owari style tsuba.
His method of creating tsuba is complicated: he puts a lot of small pieces of a hard steel between the steel layers during the fold welding work.
I think it is a good method how to make a good copy. But I can't see if the Owari tsuba smiths take such a complicated method, for what?
It may be not the original way of old Owari tsubas' days.
Here is a problem: is tekkotsu designed or does it appear naturally by long time wearing of a tsuba?
This has created a problem for people who evaluate tsuba.
Sometimes we can find a tsuba with many visible tekkotsu so it looks to be designed, made consciously.
On the other hand, tekkotsu on some tsubas looks very natural so it seems to come from many years of wearing.
This tsuba has some powerful tekkotsu, not only on the rim but also on the very surface.
When I got this tsuba, I believed this tekkotsu had appeared naturally by wearing because this tsuba has a fine radial pattern on both surfaces.
If the maker made tekkotsu consciously, such file work was not necessary.
At the time this tsuba was born, it must have had a plain shape and fine finishing.

I think, some tekkotsu could come into naturally. Then some samurais appreciated it so much as it increased the value of the tsuba. Perhaps this motivates some tsuba makers to create tekkotsu.
But we don't appreciate such purposed tekkotsu as well as naturally coming tekkotsu even if it is very visible.
We appreciate a natural feeling.
An example of fake tekkotsu
The signature is "Nobuie"
This is a product in 19th century copying the Nobuie in 16th century. But the signature may be put recently.
It has very uneven surface on the rim but it is not tekkotsu. It is designed by the tsuba maker.
The top of the tekkotsu-like rib is not smooth as natural tekkotsu. It doesn't look made by long time worn out.
Probably the maker wanted to express a powerful feeling, but the result smells purposeful.

I can think out several methods of the tsuba with natural tekkotsu.
Tsuba is not a blade, therefore the material is not necessary to be as fine as for the blade.
The cheaper steel may be enough to make a simple tsuba.
One block of TAMAHAGANE does not have a uniform quality inside of itself, and in the cheaper tamahagane, the differences are bigger.
Rough quality of tamahagane and a few times fold welding, such method will create a tsuba plate with irregular hardness inside.
In a work shop of a blacksmith for tsuba/armour, there is always a lot of small cut-out pieces that came from tsuba/armour making process.
In old days the smiths did not throw it away because iron/steel was very expensive.
So they stored it and used it again as the material, sometimes for a tsuba.
To weld such small pieces together, and to fold it a few times, it may be good enough for a tsuba, because every piece is already refined by fold welding when it was used to make armours.
Such steel can become a fine plate although of uneven quality .
After 16th century, some iron tsubas were made of three layered steel, a sandwich like construction.
Both the surface/outer steels are fine, while the core is not.
Such tsuba has a long furrow lined tekkotsu on the rim.