Brian Whatcott wrote in message . ..
As it happens, the Whitworth profile DOES have a radiused root.
Still, the caution is well-founded.
One can only suggest that it is better to clean up a thread with a die
nut than force the threaded connection to engage, on a lesser of two
evils basis.

Not the lesser. Regardless of profile, a rolled thread is rolled for
a good metalurgical reason, and is no longer a rolled thread when
recut with a die (outer grain structure altered). Any way you cut it
(pun) metal is being removed where a thread was rolled so that no
metal would be removed. This is why replacement fittings are made,
and which likely cost less than what the OP may pay for threading
tools + shipping & time. If it won't clean up well enough on a wire
wheel it should be tossed. Sounds like a turnbuckle & we know they
only fail when it is *very* inconvenient.