[Lynn Eades]

I was only ever talking about the finished length of the rod, including the threads and nothing extra. I'm sure I have already covered this. (see line 5 first post)

The rod is a medium tensile, which is what you would require. You have to be able to put a thread on it, but you want it strong.
Free cutting mild steel has a lower tensile strength than mild steel (mild steel doesn't have a spec) It is higher in lead content to make the thread cutting easier. It is not suitable for this job.

On the thread cutting;
It is easy to screw it up! (start it crooked)
When you buy your steel for your long rods, and you have cut them to length, you have only one shot at it.
The best way to do it (unless you have access to special thread rolling gear) is to put the rod in a lathe (chuck) and your die holder against the spindle of the tail stock.
This helps you to keep it all square for the thread cutting
You can then "feed' the die with the tail stock, while turning the chuck by hand (maybe easier swinging it with the chuck key)
It the case of the long rods, careful planning to support the rod is required (maybe put it in a pipe that fits in the hole through the headstock and supporting the other end with a stand or timber frame or what have you) Make sure the lathe is isolated (switched off at the main) or serious damage is likely.