Meredith,

I suggest that you try sapphire or ruby balls from Small Parts Inc ( 
www.smallparts.com) For a couple of bucks apiece you can get grade 25 
balls that are highly polished and round to within .000025". These are 
used commercially as indicator tips and probes for coordinate measuring 
machines. They have excellent physical properties as well.

Dave...

meredith lamb wrote:

> Hi all,
>
> Haven't yet tried such; but it is obvious that there are various size 
> glass round balls
> around that could (?) be tried as a dual spaced pivot part of a seismo 
> hinge.  The
> contact surfaces for such could also be a flat glass, or of course, a 
> variety of other
> materials.  Probably for weight pressure limitations they may best 
> work for S-G's
> (vertical hanging mass pendulums), with lighter overall boom/mass weights.
>
>
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