I really like the texture in the bolt rendering by Jaime.
http://www.ignorancia.org/en/index.php?page=Bolts_still
(I think he used a simple sphere sweep for the thread )
My own texture was a bit of a failure :-)
http://news.povray.org/povray.binaries.images/thread/%3Cweb.413aea09e929ab82a8399d8d0%40news.povray.org%3E/?ttop=235638
&toff=2050
