On Aug 21, 2:01 pm, mkr5000 wrote:
I don't know why but I've been in this force of habit getting some of
my small parts quoted in 5052 aluminum.

I just compared the price of a certain part done in steel and I'm
saving over 50%

What is the typical (common) grade of steel that is used in parts
where the thickness is anyhwere from 050 to 062 (all I ever use) and
the part may also have some 90 degree bends, some small holes etc.

Typical (and most inexpensive) material for electronic chassis and the
like.

I assume you mean sheet metal parts although some of those steels
imply machined bar, rod or tubing.

In small quantities aluminum usually is best overall because you don't
have to finish it, although you can paint or plate or brush or anodize
it if you want to. 6061-T6 is the most common grade for electronics, I
think because it's the strongest alloy that can be bent with few
problems, and welded. 5052 is somewhat weaker and bends to a sharper
corner without cracking. The higher performance alloys all have some
gotcha like brittleness or welding issues, the softer ones are better
for severe forming but aren't stiff enough when flat. Bud chassis
boxes are a good example, they deform easily and don't hold screws
well.

The price of aluminum seems to vary wildly between suppliers, I don't
know why. I've been quoted $60 for a 4X8 sheet from one local dealer
and over $200 from another.

"Cold Rolled Steel" or CRS around 20 to 26 gauge (~ 0.018" - 0.036")
is similar in stiffness to 0.050 or 0.062 aluminum. It's used to
repair car bodies, often in thinner gauges, and for sheet-metal
furniture and appliances. Some of its strength comes from the cold
rolling so you can't compare it directly to hot-rolled steel of
similar carbon content like A36. It's almost always plated or painted
or powder-coated even for indoor use. Some people's fingerprints will
rust it.

Hot rolled steel is the cheapest to buy and most expensive to finish.
A36 is a common type. It's easy to weld and generally used where
strength counts more than appearance.

Galvanized sheet steel is CRS with a zinc coating which protects it
from rusting, including the cut edges. I've used it for electronics
where I needed magnetic shielding and didn't have enough Mu metal. It
works about as well as aluminum but it doesn't look as good and
doesn't hold paint well. It's used for heating ducts so it's available
in small amounts, which can be a problem for metals. The largest local
dealer had a minimum order of $500 last time I checked.

There's a type of galvanized or zinc-primed or whatever steel with a
matte grey finish used for computer internals that could be the best
answer if you can find some. Common bending machines might scratch the
coating. The undersides of my SUV and truck are made of something
similar.

12L14 and its free-machining buddies make life easier for the
machinist but it rusts badly, as does chrome-moly.

A stainless steel such as 304 could be worth considering. It's more
durable than aluminum for things that will be banged around and also
doesn't need expensive finishing. Some types like 302 made decent flat
springs for no-tool panel latches.

I ask the shop for their recommendations and see if I can save money
by fitting my design to their standard practices, for instance not
calling out holes they can't punch or bends beyond their brake's
capacity. The setup is a large part of the cost for a small batch of
parts.

I set up a home shop substantially to learn materials and
manufacturing processes so I could design a $5 bracket that didn't
cost $3000 to make. Electrical engineers rarely know much about
mechanical engineering or production and too often make very expensive
design decisions. My machine tools are far too old, slow and small for
economical production - that's why they were available cheap - but
they are good enough to make a single prototype or machine a small
emergency batch of simple parts that the sheet metal shop fabricating
the job couldn't handle. Often I notice an improvement or interference
when making prototypes that I missed when drawing them.

Jim Wilkins