In message , Dave Plowman
writes
In article ,
The Natural Philosopher wrote:
I think the term you were looking for was "stripped" rather than
"threaded", i.e. "I have stripped the head on the bolt". Or maybe the
technical term "knackered" would be better.

Abd of course the stud extractor - a reverse threaded self tap screw
with a socket top...it screws in to any hole anti-clockwise and jams
there. Used for pulling broken studs out of almost anything.

Usually called Easi-out. They either split the top of the screw due to
side forces caused by the taper, or break off and are impossible to drill
out due to being made of hardened steel. Make sure you buy good quality
ones - market stall ones are usually just rubbish.

And when the tip breaks off, you are truly in the ****

experience talking here
--
geoff