Tim Mitchell wrote:

In article , The Natural Philosopher writes

Dan Gravell wrote:

Hi there,
I have a very small allen key screw which screws into the bottom of
my shower mixer unit to fasten the thermostat and control to the
shower.
I recently had some problems with the shower running colder than
normal so following the advice of the manual (and this newsgroup) I
took out the thermostat, flushed it and gave it a good clean, and
reinserted it. Unfortunately this didn't work, and after a phone
call to the manufacturers I got sent a new unit (can't fault the
service btw, the company was Marflow).
Now, the problem is that when I went to install the thermostat, I
realised the screw's inside has become threaded, in that it is almost
circular and not hexagonal any more. The allen key (which I suspect
was probably slightly too small in the first place) just rotates in
the socket. This "threading" happened when I rescrewed after trying
the flush.
I tried extracting with all manner of pliers, assuming I could get a
decent grip and twist it out, but to no avail. Perhaps I screwed it
in incorrectly.
Anybody got any suggestions for extracting this screw? I thought
possibly using a junior hacksaw to create a slot to use a normal
screwdriver to screw it out. Would that work? Or would it just mangle
the screw?
Thanks, Dan
p.s. Sorry if threaded is not the proper term... Perhaps someone
could suggest a better one to help other people searching for
similar problems.


You have had one good suggestion - glue in the key.

Another one is to invest in a small file, and an over seze allen keye,
and file it down rather tapered til its a very tight fit, and hammer
it in.

Also I have sometimes managed to get them out using a flat blade
screwdriver which fits across two corners of the hexagon.

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.