What you really want is one of the old Di-Acro shears. Good luck
finding one of those though.
Currently, I’d avoid harbor freight like the plague. My old shop had
one of their guillotine shears. It was marginally better than
hacking the sheet apart with an axe, but not much.
I’ve heard good things about the new Durston shear. Haven’t seen
one, but the build quality on their rolling mills is impeccable, so I
can’t imagine the shear is anything less than very good. The drawback
is price. (on the other hand, if you can possibly stretch to afford
it, you won’t regret it.)
16-18 ga copper is pretty thick. You’re going to be right at the
very edge of what the cheapo shears can handle, and they won’t do it
well. You’re probably better off biting the bullet, and getting a
Might be worth contacting some of the used tool folks to see if
there’s a used shear floating around anywhere. (Otto Frei sometimes
has used tools, Gold Machinery in RI is nothing but used tools.
There’ve been others listed here on Orchid recently, but I can’t
remember under what thread.)
For whatever that all’s worth.