you're probably going to hurt yourself, and destroy the nibbler.
the gauge of steel used in some cases is more than some nibblers can handle, and it's hardened's steel, not just any steel.
you are much better using a drill and jigsaw with a bimetal blade.
as for ppl who use dremels, it's for modeling, and small scale finishing. you may as well use a spoon to dig a grave.