On Tue, 01 Feb 2005 11:53:54 +0000, the inscrutable
spake:
This is because it uses Alnico type metal magnets
which must NEVER be removed from their associated pole
pieces (not even for milliseconds!) unless you have the
facilities to re-magnetise in situ after final assembly.
That's dibble and fluff. Alnico magnets do decay, albeit slowly (over
years). But no magnetic base uses a "keeper" while it's in use (none I know
of have a keeper, at all), or it wouldn't stick to anything. The keeper is
designed to _complete_ the flux circuit, in order to lengthen the life of
the magnet. If the circuit were completed with a keeper (shunting the field
between the poles), the magnet couldn't stick to your work surface.
He's confused.
More likely, anyway (if the base is relatively new - say twenty years or
less), it has a ceramic/ferrite magnet. They hardly decay in strength at
all, with or without a keeper.
LLoyd