Robert Roland wrote:
On 27 Jul 2008 01:25:20 GMT, "DoN. Nichols"
wrote:


There are things which are die cast and then machined to final
dimensions in some places like automobile engine pistons.


Hard drives definitely fall into this category. The seat for the
spindle motor, the mount for the head pivot and the edge which
contacts the lid are machined. The machined surfaces are very shiny
and seem to resist oxidation very well.
Floppy drives and some CDrom drive frames are die cast zinc.
Not worth a whole lot. Hard drives are almost always cast
aluminum, worth a lot more. You can tell, as the pot metal is
brittle as can be, the aluminum is quite malleable. You can
also tell by "ringing" them. The pot metal rings with a loud,
long high-pitched sound, the aluminum goes thunk.

Oxidation is another indication, most aluminum cast alloys are
pretty oxidation resistant (after the fist layer forms in
seconds). The pot metal turns very gray after a while.

Jon