Punching through two sheets of steel....

[220/221]

When I was an apprentice, I pulled a 1" punch thru backwards using a ratchet punch

It punched the hole (not too cleanly) and didn't break anything. I remember thinking "This sure is hard. The punch must be dull"

The only punch failures I have had is when the guys don't screw the nipples in all the way and the threads strip (twice).

 

[LarryFine]

I remember thinking "This sure is hard. The punch must be dull"

And the guy you were working under probably thought the same thing about you.

 

[hunt4679]

If you punch it it will more than likely streatch your die and next time you use it it will leave a burr around the hole. Use an oversized hole saw for at for one layer then punch the other so you still have the fit of a punched hole