What I do is half a turn, back a quarter, and then repeat,
rather in the style of tapping a screw thread, using Rocol
also in the same style.

In this case, after 3 1/2 turns I reached the obstruction,
and retracted to examine. There didn't appear to be any obstruction
in the thread, although it was difficult to see because it was down
an aluminium tunnel, and so I applied greater force for the next
half turn, at which point it jammed up, and so reference to
this NG!

Odd that even a direct practical and technical question such
as this matter brought so many of the resident CB types out
of the wood work to sneer 'n' jeer on the sidelines. Their
behaviour in this public forum perhaps does more to create
a bad press for HamRadio and to lower the standards
than they perhaps realise?

"KW" wrote in message
...
"Airy R. Bean" wrote in message
...
It is standard practice when you have a tight/rusty
screw but neither the tap nor the die for the thread
to drive a nut against the corrosion.
You can tighten slightly the nut on the screw then tap the around sides of
the nut freeing off the thread. next tighten down again and repeat until
sufficiant thread is compatible with the nut.
BTW... don't change the nut for another.