On Sat, 27 Sep 2008 13:47:26 -0700 (PDT), Rob wrote:

Thank you all.
I do have a lot of the tools suggested, next week I will be picking up
my plasma cutter.
For the duct work. I don't want to compete with the pieces which you
can by at the locale hardware shops.
I want to do the items which a unique to each job. Specialty items.
What size of brake would be required? I am looking at a 50" box pan
brake with interchangeable dies.
Who would be a good source to buy some of the pieces?
This might be a strange question but are there any books available? I
have worked with metal for a while but more on a milling machine and
not sheet.

Thanks,
Rob

The air conditioning stuff is usually done as flat sheets with the
edges formed to lock together, like forming big bends and transitions.
Long sections of square duct are done as two L's that button-lock
together, and use S and Drive style splines to lock lengths together.

Another way to do big ducts is form rolled strip stock into
Spirolock round duct - it would look like a barber pole if painted
along the seam. Perfect for use with exposed ceilings in "industrial"
styled buildings. Can come off the machine as long as you need, but
for practical purposes you want to make the sections 8' to 12' long
for ease of handling, then flange one end and crimp the other so they
couple together.

If you do ductwork, you also need gear for handling the blanket and
semi-rigid fiberglass insulation on the inside. Round ducts are easy,
they ship the insulation pre-formed in rigid tubes to slide inside -
but you have to cut it into wedges yourself to line segmented elbows.

And remember that you can easily price yourself out of the market -
I've done a lot of AC ductwork with raw sheetmetal and hand benders,
pop rivets and "sharps" screws, only because the sheetmetal shop was
WAY too proud of their custom work. It's not a Museum Piece, even
though it may be air conditioning a museum... ;-)

-- Bruce --