DoN. Nichols wrote:
On 2008-07-26, TwoGuns wrote:
Last month I bought about 50 damaged computer hard drives from a local
computer repair shop. I salvaged the magnets, motors and assorted
bearings, nuts and screws. The cases and circuit boards were loaded up
to take to a local metal recycler. I had called them before the trip
for a price check. They were paying $.68 for Aluminum unless it was
die cast. If it was die cast Aluminum the price was only $.34. Of
course when I get there they say it was all die cast. It was too
damned hot & humid to argue and I sure as hell didn't feel like taking
the junk back to the shop so I let them take it. Just for future
reference what is the difference between die cast Aluminum and the
higher grade and how can I tell?
The shape! Look at the parts. If they show precisions complex
shapes without machining marks, they were die cast. That is how they
were made, and the only logical way to make things like the housings for
hard drives. If you had to machine them -- even with a very fast CNC
mill -- the cost of production would be very high. Just think of how
many pounds of aluminum would have to be machined out of a solid block.
The die cast aluminum would be worth more to a hobby caster.
It is a different alloy which flows better in a die to make complex
shapes. But it is not as strong an alloy. And it may be that the other
components of the casting alloy would fight trying to make a harder
alloy from it.
There are things which are die cast and then machined to final
dimensions in some places like automobile engine pistons.
I had hit the tops of several cases
with a grinding wheel and if it showed shiny and bright I figured it
was a higher grade. What I assumed was die cast had a dull finish when
hit with a grinder.
Why?
I know they are full of **** at the recycler but I
didn't have enough information to make my case.
They called it right. No sane manufacturer would make those
housings by any way other than die casting -- except perhaps for
machining one or two prototypes to test out a design.
I was surprised at the price they paid for old circuit boards ($2.40/
pound but it takes a lot of circuit boards to make a pound of them.
The higher quality circuit boards may have a very thin coating
of gold on the traces overall (especially from makers like Tektronix),
and thicker coatings of gold on the fingers of edge connectors. This is
probably what brings up the value more than anything else.
I
do have a nice assortment of small bolts & screws though. One of them
was a perfect fit in a pair of old eyeglass frames I have on hand.
Most of the screws are probably metric sizes based on my
experience.
Enjoy,
DoN.
I only disagree in the statement of the strength of the die cast
material. This is a common misconception. The fact is, die cast alloys
are stronger in many ways than aluminum. Most approach the
characteristics of cast iron. Try to make those thin sections in
aluminum and see how long the part holds up!
http://www.eazall.com/materialproperties.aspx
ZA-12 or ZA-27 are excellent choices for making (casting) homebuilt
machines, like the gingery series, or for making jigs and fixtures. If a
wear surface is needed, it is a simple matter to include a piece of steel.
The greatest thing about ZA alloys for the home shop is it can be melted
without a furnace.
No, I don't sell ZA alloys, I just love to work with them.
--
Ron Thompson
Riding my '07 XL883C Sportster
On the Beautiful Florida Space Coast,
right beside the Kennedy Space Center,
USA
http://www.plansandprojects.com
My hobby pages are he
http://www.plansandprojects.com/My%20Machines/
Visit the castinghobby FAQ:
http://castinghobbyfaq.bareboogerhost.com/
Add yourself to the member map he
http://www.frappr.com/castinghobby
Want to have some fun? The next time you're at McDonald's, wait until
the kid has your change ready and then say "Wait, I've got the two cents."
-Ron Thompson