Peter - I am not trying to be a wise guy here, but why would you want
to make your own? You can buy a 10' stick of Z to accommodate many
different sizes of material for about $4.

I do a lot of repairs, and bend a lot of flashing. But unless you
know what you are doing with sheetmetal, it can be very time
consuming, tedious and the material unforgiving. In other words, a
PITA.

Believe me, nothing made out of wood will give you crisp, perfect,
hard edges. That takes a real brake adjusted correctly, with clean
crisp fingers. Personally, with that in mind I never bend anything I
can buy.

But... if you need a to bend your own metal to specific sizes, you can
DAGS a "homemade sheet metal brake", "hobby metal brake" and a few
other search phrases and come up with a ton of info.

Robert