Harry I was just looking over your pictures again and I noticed it seems you are using "galvanised" all thread.
I am not saying it won't work but the galvanised thread offers a great deal more resistance to the nut than does the zinc all-thread. In addition I have found that a lot of the galvanised all-thread has great lumps of "galv" in places which will need to be cleaned off.
Running a "thread chaser" or die over it may help although that will likely remove quite a bit of the galv and hence may cause the threaded rod to rust.
Also it looks as though it is a 5/16 or 3/8 rod. Nothing wrong with that but be aware that as a result of that it will have a coarser thread and using a coarser thread will give you less resolution than the finer 1/4" all-thread - 20 tpi that I use.
Unfortunately the zinc plated all-thread is only available in Australia in imperial sizes - I personally don't find that a problem - but a younger chap like yourself may object to it.
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