Good advices for a newbie (threading tools lathe)

[C-Bag]

Hi Stefano, and welcome.

I'm new to threading on the lathe too, but there is a lot of folks on here like Paul and Marv who can help.

Just to be clear, the units in picture #5 are audio tweeter horns or wave guides, correct? And you are wanting to make larger versions of these? Are the drivers you are wanting to thread into the horns threaded?

I personally learn a new process best when I have a project, just like yours. I would think your first step would be if you have threads on the driver to use a thread gauge to determine the thread pitch. Then check your lathe gears to see if you have the correct gears to make that pitch. There are lots of great videos on YouTube on threading. Sorry if you already know all of this.