On Fri, 2 Jul 2010 05:40:44 -0700 (PDT), Owain wrote:

Half a copper ball-cock ball?

6" copper float about a tenner from BES, 8" also available.

Good bit of lateral thinking, bit big for a the top fo 4" post but

Probably easier to panel-beat an attractive dimpled finish into an
existing hemisphere than try and form a hemisphere from flat sheet.

I agree, I'm no panel beater but just thinking about how a flat sheet
of metal will need to stretch and bend to form a hemisphere is
non-trivial. One might be able to get a half hemisphere without a
skirt fairly easily but a full one which self forms to a skirt would
be much harder.

--
Cheers
Dave.