DoN. Nichols wrote:
On 2010-07-08, Bob La Londe wrote:

"Buerste" wrote in message
...

"Bob La Londe" wrote in message
...

I need to figure out a way to punch out shapes from .025 aluminum sheet.


[ ... ]


Tell me about your press.

Well, I just have a generic open frame 12 ton air over hydraulic H-frame,
but I was thinking something like a compound lever action arbor press might
work better if it will produce enough force.


Make your punch and die out of O-1, you can

I'll have to look see what O-1 is. If it machines well I guess I could just
make it with my little mill easily enough.


O-1 is a high carbon oil hardening tool steel. You heat it up
until it no longer attracts a magnet, then quench it in oil. Then, if
you don't want it to be too hard and brittle, heat it up again, to a
temperature determined by what hardness you want. I would suggest about
Rockwell C 59 to 61 as being reasonable. From the tables in:

http://www.artmetal.com/files/import...es/O1tech.html

you heat it to about 475 F (should be able to do it in the kitchen oven,
if SWMBO does not object).

I mentioned to a friend recently that the dishwasher would be a good
way to clean some copper parts prior to patination. The alkali nature of
the wash agent being good at removing finger prints etc. Apparently that
and the patination worked a treat although she said her husband did give
her a few odd looks when he saw the stuff in the dishwasher, it didn't
bother her.


They suggest an hour per inch of thickness to get the tempering
done all the way through.


harden it easily with an OA torch and quench it in oil. Easy-peasy! I'd
be glad to quote the part if you like.

Hmmm.... that is an option.


Since you want a precise clearance between punch and die, and
since the steel expands slightly when hardened -- you want to make it
with overlap between the punch and die, and after hardening, use a die
grinder to adjust to the desired final dimensions.

Make the hole too small, because it will grow with the material
surrounding it. Make the punch just slightly too big to give room to
grind back to a clean surface.

BTW You want the hole in the die to be the right size at the surface,
and to taper larger behind the surface, so you don't wind up
with the slugs getting stuck in the dies. (Especially here,
where the slug is what you actually want to make. :-)

I *think* (but you should verify this first) that the usual
clearance angle in the die is 7 degrees.

Good Luck,
DoN.