for all my metalsmithing friends:
buy these. buy these. buy these.
(I think you can get them on amazon for ten bucks-ish)
JOYCE CHEN SHEARS
if you've been in the studio with me, you'll know I'm not a big fan of the hand shear. I will tell you to saw it out. I honestly met a woman in Atlanta this past week who said "I never saw anymore".
personally, I wouldn't go that far, but I did cut a piece of 20g sheet with great accuracy & zero warping/distortion.
THE TRICK IS TO KEEP THE BOTTOM BLADE IN COMPLETE CONTACT WITH THE SHEET, the whole time you are cutting. it feels awkward at first, but prevents warping. entirely. I promise you.
you may never saw again