This is for stove register plate.

1.5mm mild steel sheet to 3mm mild steel angle

Can't get to other side to fit nut.

Self Tappers do it? or too thick?
I may just pop rivet it on as I'm unlikely to need to dismantle it and not
the end of the world if I do have to, almost as quick if not quicker to
drill the heads off.

Also need to fix the sheet to concrete don't want to use sleeve anchors -
need a nice finish ie pan head.
Concrete is a bit crumbly. Can't use plastic plugs - must be heat proof or
can I? How hot will the perimeter get?

--
Mike W