Hi iacdxb,
Thanks for the image that helps to get closer.
Let’s see what we have
The bottle-thread that you show, as you mentioned, has three threads,
each of them is starting 120º apart.
A fair assumption is, that they stop as well 120º apart.
A little bit more unclear, based on just one image, how much they overlap, roughly 40-50º seems plausible.
The steep value of the thread isn’t really precisely to catch, as the camera was too close and the lens based on the distance too wide. I prefer a 500 or even 1000mm lens and go as far as possible away, to get a nearly orthogonal shot of the subject. (I use a cheap Mirror lens for that, four decades old). Top, front and side. Works great.
To evaluate what you need, here is a set up as an example: (The focal length depends on the object size in question)
https://www.amazon.com/clouddrive/share/Y98KFu9SIgBBCk3jjFDAonYplCbqj1yALSxwusuufLo
So, having nit picked on that image (sorry about that, but I did so more to excuse my rough estimations), I would say we need a plane (overall) with a ratio of 1:18 (+/-). That is the minimum in height when its done, so we need more. Given the
Since it is clear that there is a tripple repetition, the polygon count horizontally needs to be dividable by three.
Three ways to model it, just one thread and bend it, clone and merge. Secondly, model only a third with a vertical cut, preferably where only one thread is in the seam. Third, and that is attached, as it allows for the simplest show and tell in the file, wrap it one time, shift it, and done. I used a segment to measure 10º so 36 segments, which allowed me then to have two segments in height creating a square, to follow my ratio from above roughly.
All other steps are explained in the tutorial. I used a different method here for the thread creation, as in first M~W (extrude inner) then M~T (extrude) with the selection intact, I pulled it a little bit down, to follow your image.
Scene file with the major steps.
https://www.amazon.com/clouddrive/share/SROTZd8yQ1zggkVgdElPNViZX6S2grLW62ZCWchmwo
Cheers
P.S.: in the file – CSTO stands for Current State To Object