Baz you can use it to tidy a thread, There is a 5 degree difference between a Whitworth and unf thread form. So I would keep the die as slack as poss to cut the minimum. I guess anything you can do is better than a knackered thread. Ron
Thanks for the suggestions Gents.
I am going to try plan B. I have plenty of spare nuts and only a couple of rough spots, so, run a nut over the rough spots with grinding paste a few times.
('Home, home on the range')
Please do not do that BAz you will destroy the thread
The trick as printed hundreds of times in motorcyclists magazines for the teens on is
Get a nut of the right thread
Slit it along the axis as close to square as you can
Flatten the cut face on what ever you want but finish on a coarse oil stone
You will now have 2 x 1/2 nuts with sharp edges
Place them as high up the thread as you can, hopefully on a good section
Clamp them together with a pair of round jawed lock jaw pliers
Lube the thread and work you make shift die down the thread to the end where most of the damage is
If it gets blunt, a few strokes on the oil stone will sharpen it back up again.
I have used this trick so many times to get me out of the poo it is not funny
Really really good for cross threaded bolts and works a treat on clutch centers & cush drives because you can start above the damage & work your way down,
Basically it is the same as the old 2 piece split dies that were adjustable to give a good fit