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? 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. I know they are full of **** at the recycler but I
didn't have enough information to make my case.

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. 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.

DL

The only thing that occurs to me is that a lot of die cast is pot metal
(Zamac), which is mostly zinc. Perhaps your recycler is assuming the
worst, i.e., that it is pot metal. But pot metal is significantly more
dense than aluminum, so it isn't too hard to tell them apart.

This page shows "cast aluminum" (not die cast specifically) as one of
the most valuable forms of scrap aluminum:
http://www.recycle.net/Metal-N/Aluminum/index.html

And this shows the lack of value in zinc:
http://www.recycle.net/Metal-N/Zinc/...affilid=100029

Your best bet, I'd say, is too check with another recycler.

Bob

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.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

DoN's pretty right on about the circuit boards, but he forgot..

A: The price of copper is skyrocketing.

B: there is gold inside many (most?) of the IC's on the board. The wires
that connect the silicon "chip" to the "lead frame" are usually gold...

C: there are a bunch of other precious metals used in many of the passive
components like capacitors etc...

--.- Dave


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.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

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.
--
RoRo

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?

Easy to tell. What shape is the part. Is it an extrusion? Stamping?
fabricated from bar stock, Sheet aluminum? It's what they usually call
clean aluminum.
Is it a shape with many small corners and holes with only a few machined
pads for parts? Small complex item? That is cast aluminum.

There is also a class called dirty aluminum. That is things like an
engine block with steel sleeves and thread inserts. Or aluminum with
heli coils in it.

The cast aluminum is classed different due to the myriad of alloys and
additives in the aluminum. It could also appear to be cast aluminum and
actually be pot metal. Or something like a VW engine block which is a
high grade of cast magnesium.

--
Steve W.
Near Cooperstown, New York

Life is not like a box of chocolates
it's more like a jar of jalapenos-
what you do today could burn your ass tomorrow!

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

"DoN. Nichols" wrote in
:


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


Automobile engine pistons are _not_ die cast. They are permanent mold
gravity cast. Die casting does not generate the required micrograin
structure for this application of aluminum alloy.
Die casting is "Pressure Casting". The molten "shot" of aluminum is
forced into the die at extreme pressure.
Permanent mold gravity casting is more of a traditional casting
technology, except the mold is a semi-permanent one made of (typically, a
special alloy of H13) steel. Although there are variations, most are of
the 5 piece inner core mold type.
There are up to 12 pieces that make up the mold, 5 inside, up to 7
outside, depending on whether the part requires flip cores or not.
Inside:
Center wedge - A tapered piece and the heart of the inner mold core. this
is a 4-way wedge.
2x side cores - these make up the inside window shape (ribs, pockets,
inner pin bore shape, etc)
2x middle cores. These are also wedge shaped to a small degree, and go
between the window cores.
2x outside cores. these make up the OD of the casting, and have a hole
for the pincores.
(optional) 2x flip cores. these are hinged outer window cores used for
generating pockets up under the 3rd groove above the pin bore for weight
reduction. These replace part, but not all of the outside cores.
2x pincores. these create the cast pin hole
1x head core. this creates the crown geometry.

After the part has solidified enough to be handled, the center wedge
pulls down, as the center wedge pulls down, it pulls the middle cores
toward the empty space left by the center wedge then down, then the side
cores are pulled inward to relase the casting. All of this is made as one
assembly. Then the head core releases. If flip cores are used, they swing
away, then the outside cores retract. The part is then removed from the
mold. Close all mold parts, insert new screen, and pour another part.

This type of mold allows you to cast pockets and other features inside
the casting that have negative draft.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

Anthony wrote:
"DoN. Nichols" wrote in
:


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


Automobile engine pistons are _not_ die cast. They are permanent mold
gravity cast. Die casting does not generate the required micrograin
structure for this application of aluminum alloy.
Die casting is "Pressure Casting". The molten "shot" of aluminum is
forced into the die at extreme pressure.
Permanent mold gravity casting is more of a traditional casting
technology, except the mold is a semi-permanent one made of (typically, a
special alloy of H13) steel. Although there are variations, most are of
the 5 piece inner core mold type.
There are up to 12 pieces that make up the mold, 5 inside, up to 7
outside, depending on whether the part requires flip cores or not.
Inside:
Center wedge - A tapered piece and the heart of the inner mold core. this
is a 4-way wedge.
2x side cores - these make up the inside window shape (ribs, pockets,
inner pin bore shape, etc)
2x middle cores. These are also wedge shaped to a small degree, and go
between the window cores.
2x outside cores. these make up the OD of the casting, and have a hole
for the pincores.
(optional) 2x flip cores. these are hinged outer window cores used for
generating pockets up under the 3rd groove above the pin bore for weight
reduction. These replace part, but not all of the outside cores.
2x pincores. these create the cast pin hole
1x head core. this creates the crown geometry.

After the part has solidified enough to be handled, the center wedge
pulls down, as the center wedge pulls down, it pulls the middle cores
toward the empty space left by the center wedge then down, then the side
cores are pulled inward to relase the casting. All of this is made as one
assembly. Then the head core releases. If flip cores are used, they swing
away, then the outside cores retract. The part is then removed from the
mold. Close all mold parts, insert new screen, and pour another part.

This type of mold allows you to cast pockets and other features inside
the casting that have negative draft.


Great description! Would you mind if I included it on the castinghobby FAQ?

Thanks,

--


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

Die cast aluminum often has a very high amount of zinc, which is used to
make the aluminum flow better when casting, but once alloyed with the
aluminum it not only weighs more, but must be separated before the aluminum
can be used on its own. Die cast aluminum with zinc must never be used in a
wet environment because of electrolosis and unfortunately it is all the
time.
Steve

"TwoGuns" wrote in message
...
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? 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. I know they are full of **** at the recycler but I
didn't have enough information to make my case.

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. 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.

DL

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

I'd say that the reason is the aluminum alloys for casting vary widely
in alloy and that makes an unknown casting harder to use. By the time
you melt a lot of it together, you probably have a pretty poor "soup".
We use 356 for the (relatively) very high tensile strength since
we make wheels that are, after heat treating, shrunk/pressed onto steel
axles and must never come loose. The 3XX series have silicon and copper
as the major alloying elements.

2XX- copper
4XX- silicon
5XX- magnesium
7XX- zinc
8XX- tin

So you can see that mixing them would make any one of them unsuitable
for any other application.

Pete Stanaitis
-------------------------------

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? 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. I know they are full of **** at the recycler but I
didn't have enough information to make my case.

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. 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.

DL

spaco wrote:
I'd say that the reason is the aluminum alloys for casting vary widely
in alloy and that makes an unknown casting harder to use. By the time
you melt a lot of it together, you probably have a pretty poor "soup".
...

True, but the OP's recycler pays $.34 for die cast and $.68 for all
other aluminum. The "all other" can vary widely in its alloy, too. If
they're paying twice as much for "all other", you'd think that they
would be more particular about its alloy.

Bob

TwoGuns wrote:
... 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. ...

Ronald Thompson "webmaster remove wrote in
g.com:


Great description! Would you mind if I included it on the castinghobby
FAQ?

Thanks,


Don't mind at all.

--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

On Mon, 28 Jul 2008 17:14:20 -0400, Bob Engelhardt
wrote:




True, but the OP's recycler pays $.34 for die cast and $.68 for all
other aluminum. The "all other" can vary widely in its alloy, too. If
they're paying twice as much for "all other", you'd think that they
would be more particular about its alloy.

Bob


Is it disingenuous to suggest that the OP should get a crucible for melting
(or pot, it's only scrap) and a length of angle iron for a mould and turn his
die cast scrap into "ingot". Then take it to the scrap yard.


Might be worth the effort for double the price G


Mark Rand
RTFM

Mark Rand wrote:
On Mon, 28 Jul 2008 17:14:20 -0400, Bob Engelhardt
wrote:



True, but the OP's recycler pays $.34 for die cast and $.68 for all
other aluminum. The "all other" can vary widely in its alloy, too. If
they're paying twice as much for "all other", you'd think that they
would be more particular about its alloy.

Bob


Is it disingenuous to suggest that the OP should get a crucible for melting
(or pot, it's only scrap) and a length of angle iron for a mould and turn his
die cast scrap into "ingot". Then take it to the scrap yard.


Might be worth the effort for double the price G

But what is the time and energy cost for that melt?

On Jul 28, 5:58 pm, Mark Rand wrote:
On Mon, 28 Jul 2008 17:14:20 -0400, Bob Engelhardt
wrote:



True, but the OP's recycler pays $.34 for die cast and $.68 for all
other aluminum. The "all other" can vary widely in its alloy, too. If
they're paying twice as much for "all other", you'd think that they
would be more particular about its alloy.

Bob

Is it disingenuous to suggest that the OP should get a crucible for melting
(or pot, it's only scrap) and a length of angle iron for a mould and turn his
die cast scrap into "ingot". Then take it to the scrap yard.

Might be worth the effort for double the price G

Mark Rand
RTFM

I am the one that asked the question originally. Actually I have
thought about saving up the next batch of hard drives I get and doing
just that. I have a good friend that is into ceramics and she will let
me use her kiln any time I need it.

I want to thank you all for the good info you have posted.

GL2

On Tue, 29 Jul 2008 12:06:33 -0700 (PDT), TwoGuns
wrote:



I am the one that asked the question originally. Actually I have
thought about saving up the next batch of hard drives I get and doing
just that. I have a good friend that is into ceramics and she will let
me use her kiln any time I need it.

I want to thank you all for the good info you have posted.

GL2


So far I have disassemble 60-odd hard drives from work at home (not counting
the ones needing to be destroyed at work due to the presence of classified
information). I Have done it to remove the useful magnets. In the forseable
future, I would hope to be raiding the scrap pile for casting metal :-)


Mark Rand
RTFM